Income Tax Disclosure [Abstract] Summary of consolidated income tax expense Income Tax Expense (Benefit), Continuing Operations [Abstract] Current Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Total current income tax expense Current Income Tax Expense (Benefit) Deferred Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Total deferred income tax expense (benefit) Deferred Income Tax Expense (Benefit) Total income tax expense Income Tax Expense (Benefit) Tax benefit of operating loss carryforwards Other Tax Expense (Benefit) Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] First Security Bank First Security Bank [Member] First Security Bank [Member] Collegiate Peaks Bank Collegiate Peaks Bank [Member] Collegiate Peaks Bank [Member] The Foothills Bank The Foothills Bank [Member] The Foothills Bank [Member] Business Acquisition Business Acquisition [Line Items] Fair value of consideration transferred Business Combination, Consideration Transferred [Abstract] Fair value of Company shares issued, net of equity issuance costs Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Cash consideration for outstanding shares Payments to Acquire Businesses, Gross Effective settlement of pre-existing receivable Business Combination, Effective Settlement of a Pre-Existing Relationship Effective Settlement of a Pre-Existing Relationship on a business combination. Total fair value of consideration transferred Business Combination, Consideration Transferred Recognized amounts of identifiable assets acquired and liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract] Identifiable assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Cash and cash equivalents Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Debt securities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Marketable Securities Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale acquired at the acquisition date. Loans receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans Receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans Receivable Core deposit intangible Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Accrued income and other assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets Amount of other assets acquired at the acquisition date. Total identifiable assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract] Deposits Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits Amount of deposits assumed at the acquisition date Borrowings Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Borrowings Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Borrowings. Accrued expenses and other liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Total liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Total identifiable net assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Goodwill recognized Goodwill, Acquired During Period Core Deposit Intangible, Weighted Average Useful Life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Subordinated Debentures Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Subordinated Debentures Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Subordinated Debentures Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative [Table] Derivative [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative, Name [Domain] Derivative Contract [Domain] Interest Rate Swap One Interest Rate Swap One [Member] Interest rate swap. Interest Rate Swap Two Interest Rate Swap Two [Member] Interest rate swap. Interest rate swap derivative financial instruments Derivative [Line Items] Forecasted Notional Amount Derivative Liability, Notional Amount Fixed Interest Rate Derivative, Fixed Interest Rate Fair Value Disclosures [Abstract] Fair value measurement of assets and liabilities measured at fair value on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Fair value measurement of assets measured at fair value on a non-recurring basis Fair Value Measurements, Nonrecurring [Table Text Block] Quantitative information about assets measured at fair value on a non-recurring basis for which Level 3 inputs were used Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Carrying amounts and estimated fair values of financial instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Debt Disclosure [Abstract] Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table] Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Residential mortgage backed securities Residential Mortgage Backed Securities [Member] Commercial mortgage backed securities Commercial Mortgage Backed Securities [Member] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Overnight and Continuous Maturity Overnight [Member] Up to 30 Days Maturity Less than 30 Days [Member] Securities Sold Under Agreements to Repurchase Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items] Repurchase Agreements Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] CDE Certified Development Entities [Member] Certified development entities. LIHTC low Income Housing Tax Credit [Member] Low-income housing tax credit. Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other assets Other Noncurrent Assets [Member] Variable Interest Entities Schedule of Equity Method Investments [Line Items] Tax credit period Tax Credit Period The period in which an investor receives tax credits from a tax credit project. Carrying value of equity investments in LIHTCs Amortization Method Qualified Affordable Housing Project Investments Tax credit compliance period Tax Credit Compliance Period The period in which a tax credit project must stay in compliance for the investor to keep the tax credits. Unfunded contingent commitments Qualified Affordable Housing Project Investments, Commitment Impairment losses Affordable Housing Project Investment, Write-down, Amount Other Expenses [Abstract] Schedule of Other Expenses Schedule of Other Operating Cost and Expense, by Component [Table Text Block] Debt Instruments [Abstract] Summary of Subordinated Debentures Terms of Subordinated Debentures [Table Text Block] Terms of subordinated debentures. Receivables [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Residential Real Estate Residential Portfolio Segment [Member] Commercial Commercial Portfolio Segment [Member] Consumer and Other Consumer Portfolio Segment [Member] Class of Financing Receivable [Axis] Class of Financing Receivable, Type [Axis] Class of Financing Receivable [Domain] Class of Financing Receivable, Type [Domain] Residential Real Estate Residential Real Estate [Member] Commercial Real Estate Commercial Real Estate [Member] Other Commercial Commercial Loan [Member] Home Equity Home Equity Home Equity Line of Credit [Member] Loan based on the equity of the borrower's residential property. Includes close-ended loans in which the borrower receives the loan amount upfront and revolving, open-ended loans under a line of credit. Other Consumer Consumer Loan [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Summary of Loans Receivable Financing Receivable, Net [Abstract] Loans receivable Loans and Leases Receivable, Net of Deferred Income Allowance for loan and lease losses Loans and Leases Receivable, Allowance Loans receivable, net Loans and Leases Receivable, Net Amount Net deferred origination (fees) costs included in loans receivable Unamortized Loan Origination Fees and Costs Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases. Net purchase accounting (discounts) premiums included in loans receivable Unamortized Discounts and Premiums on Loans Amount of premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Weighted-average interest rate on loans (tax-equivalent) Weighted Average Interest Rate on Loans Weighted average interest rate on loans. Quarterly Financial Information Disclosure [Abstract] Summarized unaudited quarterly financial data Quarterly Financial Information [Table Text Block] Other Expenses Other Income and Expenses [Abstract] Consulting and outside services Consulting Fees Consulting fees other than legal and accounting fees. Mergers and acquisition expenses Business Combination, Integration Related Costs Debit card expenses Debit Card Expense Debit card expense. Telephone Telephone Expenses Telephone expenses Employee expenses Miscellaneous Employee Expenses Miscellaneous employee expenses other than compensation and benefits. Business development Business Development VIE amortization and other expenses VIE Write-downs, Losses and Other Expenses Write-downs, Losses and Other Expenses related to Variable Interest Entities. Loan expenses Loan-Related Expenses Loan-related expenses. Printing and supplies Supplies Expense Postage Postage Expense Legal fees Legal Fees Accounting and audit fees Accounting Fees Accounting Fees Checking and operating expenses Deposit-Related Expenses Deposit related expenses other than interest expense. ATM expenses ATM Expenses ATM Expenses Other Other Cost and Expense, Operating Total other expenses Other Noninterest Expense Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Federal and State Income Taxes Income Tax Disclosure [Text Block] Investments, Debt and Equity Securities [Abstract] Debt Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Capital Leases and Operating Leases Future Minimum Payments Due [Abstract] Capital leases and operating leases future minimum payments due. Capital Leases Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] For the Year Ended December 31, 2019 Capital Leases, Future Minimum Payments Due, Next Twelve Months For the Year Ended December 31, 2020 Capital Leases, Future Minimum Payments Due in Two Years For the Year Ended December 31, 2021 Capital Leases, Future Minimum Payments Due in Three Years For the Year Ended December 31, 2022 Capital Leases, Future Minimum Payments Due in Four Years For the Year Ended December 31, 2023 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Total minimum lease payments Capital Leases, Future Minimum Payments Due Less: Amount representing interest Capital Leases, Future Minimum Payments, Interest Included in Payments Present value of minimum lease payments Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments Less: Current portion of obligations under capital leases Capital Lease Obligations, Current Long-term portion of obligations under capital leases Capital Lease Obligations, Noncurrent Operating Leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] For the Year Ended December 31, 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months For the Year Ended December 31, 2020 Operating Leases, Future Minimum Payments, Due in Two Years For the Year Ended December 31, 2021 Operating Leases, Future Minimum Payments, Due in Three Years For the Year Ended December 31, 2022 Operating Leases, Future Minimum Payments, Due in Four Years For the Year Ended December 31, 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Minimum Lease Payments Operating Leases, Future Minimum Payments Due Total Operating And Capital Leases Future Minimum Payments Due [Abstract] Operating and capital leases future minimum payments due. For the Year Ended December 31, 2019 Operating and Capital Leases Future Minimum Payments Due Current Operating and capital leases future minimum payments due current. For the Year Ended December 31, 2020 Operating and Capital Leases Future Minimum Payments Due in Two Years Operating and capital leases future minimum payments due in two years. For the Year Ended December 31, 2021 Operating and Capital Leases Future Minimum Payments Due in Three Years Operating and capital leases future minimum payments due in three years. For the Year Ended December 31, 2022 Operating and Capital Leases Future Minimum Payments Due in Four Years Operating and capital leases future minimum payments due in four years. For the Year Ended December 31, 2023 Operating and Capital Leases Future Minimum Payments Due in Five Years Operating and capital leases future minimum payments due in five years. Thereafter Operating and Capital Leases Future Minimum Payments Due Thereafter Operating and capital leases future minimum payments due thereafter. Total Minimum Lease Payments Operating and Capital Leases Future Minimum Payments Due Operating and capital leases future minimum payments due. Goodwill and Intangible Assets Disclosure [Abstract] Goodwill Roll Forward Goodwill [Roll Forward] Net carrying value at beginning of period Goodwill Acquisitions and adjustments Net carrying value at end of period Equity [Abstract] Stockholders' Equity Note [Abstract] Stockholders' Equity Note [Abstract] Accumulated Other Comprehensive Loss [Table] Accumulated Other Comprehensive Income (Loss) [Table] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Available-For-Sale Debt Securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Derivatives Used for Cash Flow Hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss) [Line Items] Balance, beginning Accumulated Other Comprehensive Income (Loss), Net of Tax Other comprehensive income (loss) before reclassification Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Reclassification adjustments for losses included in net income Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Reclassifications to retained earnings Reclassification from AOCI, Current Period, Tax Total other comprehensive (loss) income, net of tax Other Comprehensive Income (Loss), Net of Tax Balance, end Banking and Thrift [Abstract] Capital adequacy guidelines and compliance Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Loans Receivable, Net Financing Receivables [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Stock-based Compensation Plan Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Schedule of Financing Receivables Past Due [Table] Schedule of Financing Receivables Past Due [Table] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Financing Receivables, Period Past Due [Domain] Accruing loans 30 to 59 days past due Financing Receivables, 30 to 59 Days Past Due [Member] Accruing loans 60 to 89 days past due Financing Receivables, 60 to 89 Days Past Due [Member] Accruing loans 90 days or more past due Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Financing Receivable, Recorded Investment, Past Due [Line Items] Financing Receivable, Recorded Investment, Past Due [Line Items] Loan portfolio aging analysis Financing Receivable, Recorded Investment, Aging [Abstract] Past due loans Financing Receivable, Recorded Investment, Past Due Non-accrual loans Financing Receivable, Recorded Investment, Nonaccrual Status Total past due and non-accrual loans Financing Receivable Recorded Investment Past Due and Non Accrual Loans Financing receivable recorded investment past due and non accrual loans. Current loans receivable Financing Receivable, Recorded Investment, Current Total loans receivable Offsetting [Abstract] Offsetting Assets [Table] Offsetting Assets [Table] Interest Rate Swaps Interest Rate Swap [Member] Offsetting Assets [Line Items] Offsetting Assets [Line Items] Offsetting Derivative Assets Offsetting Derivative Assets [Abstract] Gross Amounts of Recognized Assets Derivative Asset, Fair Value, Gross Asset Gross Amounts Offset in the Statements of Financial Position Derivative Asset, Fair Value, Gross Liability Net Amounts of Assets Presented in the Statements of Financial Position Derivative Asset, Fair Value, Amount Not Offset Against Collateral Mergers and Acquisitions Mergers, Acquisitions and Dispositions Disclosures [Text Block] Borrowings Debt Disclosure [Text Block] Fair value measurement transfers from one level to another Fair Value Measurement Transfers From One Level To Another Fair Value Measurement Transfers From One Level To Another Fair Value Option, Disclosures [Table] Fair Value Option, Disclosures [Table] Loans Held For Sale [Member] Loans Held For Sale [Member] This item represents loans held-for-sale including, but not limited to, mortgage loans and finance receivables. Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Gain (Loss) on Sale of Loans [Member] Gain (Loss) on Sale of Loans [Member] Primary financial statement caption encompassing gain (loss) on sale of loans. Fair Value, Option, Quantitative Disclosures [Line Items] Fair Value, Option, Quantitative Disclosures [Line Items] Fair Value, Option, Changes in Fair Value, Gain (Loss) Fair Value, Option, Changes in Fair Value, Gain (Loss) Summary of loans receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Summary of the activity in the ALLL Allowance for Credit Losses on Financing Receivables [Table Text Block] Summary of recorded investment in loans and the balance in the ALLL Summary of Recorded Investment in Loans and ALLL on Portfolio Class Basis [Table Text Block] Summary of recorded investment in loans and ALLL on a portfolio class basis. Loan portfolio aging analysis Past Due Financing Receivables [Table Text Block] Summary of the impaired loans Impaired Financing Receivables [Table Text Block] Summary of TDRs Troubled Debt Restructurings on Financing Receivables [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Nonrecurring Measurements Fair Value, Measurements, Nonrecurring [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets with a recorded change from re-measuring at fair value on a non-recurring basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract] Other real estate owned Other Real Estate Owned Fair Value Disclosure Other real estate owned fair value disclosure. Collateral-dependent impaired loans, net of ALLL Collateral Dependent Impaired Loans Owned Fair Value Disclosure Collateral dependent impaired loans owned fair value disclosure. Total assets measured at fair value on a non-recurring basis Assets, Fair Value Disclosure Effective income tax rate reconciliation Effective Income Tax Rate Reconciliation, Percent [Abstract] Federal statutory rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent State taxes, net of federal income tax benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Tax rate change Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Tax-exempt interest income Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent Tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Other, net Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective tax rate Effective Income Tax Rate Reconciliation, Percent Subsequent Events [Abstract] Subsequent Event Subsequent Events [Text Block] Consideration transferred, identifiable net assets acquired and resulting goodwill Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Unaudited Pro Forma Summary of the Company as if the 2018 Acquisitions had Occurred at the Beginning of the Period Business Acquisition, Pro Forma Information [Table Text Block] Unaudited Pro Forma Summary of the Company as if the 2017 Acquisitions had Occurred at the Beginning of the Period BusinessAcquisitionProFormaInformationPriorYearTextBlock [Table Text Block] Business Acquisition ProForma Information Prior Year TextBlock [Table Text Block] Statement of Cash Flows [Abstract] Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Net Income (Loss) Attributable to Parent Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Provision for loan losses Provision for Loan, Lease, and Other Losses Net amortization of debt securities Accretion (Amortization) of Discounts and Premiums, Investments Net accretion of purchase accounting adjustments Accretion (Amortization) of Discounts and Premiums, Business Combinations The sum of the periodic adjustments of the differences between business combination asset and liability fair values and carrying values that are charged against earnings. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method. Amortization of debt modification costs Amortization of Debt Issuance Costs Origination of loans held for sale Payments for Origination and Purchases of Loans Held-for-sale Proceeds from loans held for sale Proceeds from Sale of Mortgage Loans Held-for-sale Gain on sale of loans Gain (Loss) on Sales of Loans, Net Loss on sale of debt securities Gain (Loss) on Sale of Investments Bank-owned life insurance income, net Life Insurance, Corporate or Bank Owned, Change in Value Stock-based compensation expense, net of tax benefits Share-based Compensation Depreciation of premises and equipment Depreciation, Nonproduction Loss (gain) on sale and write-downs of other real estate owned, net Gains (Losses) on Sales of Other Real Estate Deferred tax expense (benefit) Core deposit intangible amortization Amortization of Intangible Assets Amortization of investments in variable interest entities Variable Interest Entities Investment Amortization Amount of amortization expense of investment in variable interest entities. Net (increase) decrease in accrued interest receivable Increase (Decrease) in Accrued Interest Receivable, Net Net decrease in other assets Increase (Decrease) in Other Operating Assets Net increase (decrease) in accrued interest payable Increase (Decrease) in Interest Payable, Net Net increase (decrease) in other liabilities Increase (Decrease) in Other Operating Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Sales of available-for-sale debt securities Proceeds from Sale of Debt Securities, Available-for-sale Maturities, prepayments and calls of available-for-sale debt securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Purchases of available-for-sale debt securities Payments to Acquire Debt Securities, Available-for-sale Maturities, prepayments and calls of held-to-maturity debt securities Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Purchases of held-to-maturity debt securities Payments to Acquire Held-to-maturity Securities Principal collected on loans Proceeds from Loan and Lease Originations and Principal Collections Loan originations Payments for Loans Originated or Acquired Payments for loans originated or acquired. Net additions to premises and equipment Payments for (Proceeds from) Productive Assets Proceeds from sale of other real estate owned Proceeds from Sale of Wholly Owned Real Estate and Real Estate Acquired in Settlement of Loans Proceeds from redemption of non-marketable equity securities Proceeds from Sale of Federal Home Loan Bank Stock Purchases of non-marketable equity securities Payments to Acquire Federal Home Loan Bank Stock Proceeds from bank-owned life insurance Proceeds from Life Insurance Policy Investments in variable interest entities Payments to Acquire Other Investments Net cash received from (paid in) acquisitions Payments to Acquire Businesses, Net of Cash Acquired Net cash (used in) provided by investing activities Net Cash Provided by (Used in) Investing Activities Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Net increase (decrease) in deposits Increase (Decrease) in Deposits Net increase (decrease) in securities sold under agreements to repurchase Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase Net increase (decrease) in short-term Federal Home Loan Bank advances Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less Proceeds from long-term Federal Home Loan Bank advances Proceeds from FHLBank Borrowings, Financing Activities Repayments of long-term Federal Home Loan Bank advances Payments of FHLBank Borrowings, Financing Activities Net (decrease) increase in other borrowed funds Proceeds from (Repayments of) Other Debt Cash dividends paid Payments of Ordinary Dividends, Common Stock Tax withholding payments for stock-based compensation Payments Related to Tax Withholding for Share-based Compensation Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash, cash equivalents and restricted cash Cash and Cash Equivalents, Period Increase (Decrease) Cash, cash equivalents and restricted cash at beginning of period Cash and Cash Equivalents, at Carrying Value Cash, cash equivalents and restricted cash at end of period Supplemental Disclosure of Cash Flow Information Supplemental Cash Flow Information [Abstract] Cash paid during the period for interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Cash paid during the period for income taxes Income Taxes Paid Supplemental Disclosure of Non-Cash Investing Activities Other Noncash Investing and Financing Items [Abstract] Transfer of debt securities from held-to-maturity to available-for-sale Transfer from Investments Sale and refinancing of other real estate owned Real Estate Owned, Transfer from Real Estate Owned Transfer of loans to other real estate owned Real Estate Owned, Transfer to Real Estate Owned Dividends declared but not paid Dividends Payable Fair value of common stock shares issued Stock Issued Cash consideration for outstanding shares Cash Consideration for Outstanding Shares Cash Consideration for Outstanding Shares Fair value of assets acquired Noncash or Part Noncash Acquisition, Value of Assets Acquired Liabilities assumed Noncash or Part Noncash Acquisition, Value of Liabilities Assumed Schedule of Financing Receivable, Allowance for Credit Losses [Table] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Financing Receivable, Allowance for Credit Losses [Line Items] Financing Receivable, Allowance for Credit Losses [Line Items] Allowance for loan and lease losses Financing Receivable, Allowance for Credit Losses [Roll Forward] Balance at beginning of period Financing Receivable, Allowance for Credit Losses Charge-offs Financing Receivable, Allowance for Credit Losses, Write-downs Recoveries Financing Receivable, Allowance for Credit Losses, Recovery Balance at end of period Gain or loss on sale of investments Gain (Loss) on Investments [Abstract] Available-for-sale Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] Proceeds from Sales and Calls of Debt Securities Proceeds from Sales and Calls of Debt Securities, Available-for-sale Proceeds from Sales and Calls of Debt Securities, Available-for-sale Gross realized gains Available-for-sale Securities, Gross Realized Gains Gross realized losses Available-for-sale Securities, Gross Realized Losses Held-to-maturity Debt Securities, Held-to-maturity, Sale or Transfer of Investment [Abstract] Proceeds from calls of debt securities Held-to-Maturity Securities, Gross Realized Gains (Losses), Sale Proceeds The total amount of proceeds received for the sale of securities categorized as held-to-maturity during the reporting period. The sale of held-to-maturity securities includes proceeds from maturities, prepayments and calls. Gross realized gains Held-to-Maturity Securities, Sold Security, Realized Gain This item represents the gain realized on the sale of held-to-maturity securities disposed of during the period. Gross realized losses Held-to-Maturity Securities, Sold Security, Realized Loss This item represents the loss realized on the sale of held-to-maturity securities disposed of during the period. Additionally, this item may include, if not separately presented, any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt securities which are being or have been recognized in earnings during the period. Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] First Company Statutory Trust 2001 First Company Statutory Trust 2001 [Member] First Company Statutory Trust 2001 First Company Statutory Trust 2003 First Company Statutory Trust 2003 [Member] First Company Statutory Trust 2003 Glacier Capital Trust II Glacier Capital Trust II [Member] Glacier Capital Trust II Citizens (ID) Statutory Trust I Citizens (ID) Statutory Trust I [Member] Citizens (ID) Statutory Trust I Glacier Capital Trust III Glacier Capital Trust III [Member] Glacier Capital Trust III Glacier Capital Trust IV Glacier Capital Trust IV [Member] Glacier Capital Trust IV Bank of the San Juans Bancorporation Trust I Bank of the San Juans Bancorporation Trust I [Member] Bank of the San Juans Bancorporation Trust I Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Subordinated debentures owed to trust subsidiaries Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Member] Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust [Member] Tier 2 subordinated debentures Junior Subordinated Debt [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Terms of Subordinated Debentures Terms of Subordinated Debentures Abstract Terms of subordinated debentures. Balance Subordinated Debt Rate at December 31, 2018 Debt Instrument, Interest Rate, Effective Percentage LIBOR Rate Spread Debt Instrument, Basis Spread on Variable Rate Condensed Financial Information Disclosure [Abstract] Condensed Income Statement [Table] Condensed Income Statement [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Parent Company Parent Company [Member] Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Condensed Statements of Operations and Comprehensive Income Statement of Operations [Abstract] Statement of operations. Income Revenues [Abstract] Dividends from subsidiaries Investment Income, Dividend Gain on sale of investments Debt Securities, Realized Gain (Loss) Intercompany charges for services Intercompany Charges for Services Intercompany charges for services. Other income Other Income Total income Revenues Expenses Costs and Expenses [Abstract] Compensation and employee benefits Labor and Related Expense Other operating expenses Total expenses Noninterest Expense Income before income tax benefit and equity in undistributed net income of subsidiaries Earnings Before Income Tax Benefit and Equity in Undistributed Earnings of Subsidiaries Earnings before income tax benefit and equity in undistributed earnings of subsidiaries. Income tax benefit Income before equity in undistributed net income of subsidiaries Income Before Equity in Undistributed Earnings of subsidiaries Income before equity in undistributed earnings of subsidiaries. Equity in undistributed net income of subsidiaries Subsidiary Income (in Excess of ) Less than Dividends Distributed Subsidiary Income (in Excess of ) Less than Dividends Distributed Net Income Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Commitments and Contingencies Disclosure [Abstract] Outstanding commitments Other Commitments [Table Text Block] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Consolidated VIEs Variable Interest Entity, Primary Beneficiary [Member] Loans Receivable Loans Receivable [Member] Accrued Interest Receivable Accrued Interest Receivable [Member] Primary financial statement caption encompassing accrued interest receivable. Other Assets Prepaid Expenses and Other Current Assets [Member] Other Borrowed Funds Borrowings [Member] Accrued Interest Payable Accrued Interest Payable [Member] Primary financial statement caption encompassing accrued interest payable. Other Liabilities Accounts Payable and Accrued Liabilities [Member] Consolidated VIEs Variable Interest Entity [Line Items] Assets Variable Interest Entity, Consolidated, Carrying Amount, Assets Liabilities Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Core Deposits Intangibles Core Deposits [Member] Finite-Lived Intangible Assets Finite-Lived Intangible Assets [Line Items] Net Core Deposit Intangibles and Aggregate Amortization Expense Finite-Lived Intangible Assets, Net [Abstract] Gross carrying value Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Net carrying value Finite-Lived Intangible Assets, Net Aggregate amortization expense Estimated Amortization Expense Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] For the year ending December 31, 2019 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months For the year ending December 31, 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Two For the year ending December 31, 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Three For the year ending December 31, 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Four For the year ending December 31, 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Five Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] Financing Receivable, Impaired [Line Items] Financing Receivable, Impaired [Line Items] Summary of the impaired loans by portfolio class of loans Summary of Impaired Loans by Portfolio Class of Loans [Abstract] Summary of the impaired loans by portfolio class of loans. Loans with a Specific Valuation Allowance, Recorded Balance Impaired Financing Receivable, with Related Allowance, Recorded Investment Loans with a Specific Valuation Allowance, Unpaid Principal Balance Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance Specific valuation allowance Impaired Financing Receivable, Related Allowance Loans with a Specific Valuation Allowance, Average Balance Impaired Financing Receivable, with Related Allowance, Average Recorded Investment Loans without a Specific Valuation Allowance, Recorded Balance Impaired Financing Receivable, with No Related Allowance, Recorded Investment Loans without a Specific Valuation Allowance, Unpaid Principal Balance Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance Loans without a Specific Valuation Allowance, Average Balance Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment Recorded balance Impaired Financing Receivable, Recorded Investment Unpaid principal balance Impaired Financing Receivable, Unpaid Principal Balance Average balance Impaired Financing Receivable, Average Recorded Investment Activity for restricted stock awards Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Maximum Number of Consecutive Quarters for Deferral of Interest Payments on Trust Preferred Securities Maximum Number of Consecutive Quarters for Deferral of Interest Payments on Trust Preferred Securities Maximum Number of Consecutive Quarters for Deferral of Interest Payments on Trust Preferred Securities Size of company eligible for Tier 1 grandfather provision Size of company eligible for Tier 1 grandfather provision Size of company eligible for Tier 1 grandfather provision. Number of Years Before Allowed to Prepay Tier 2 Subordinated Debt Number of Years Before Allowed to Prepay Debt Number of Years Before Allowed to Prepay Debt Property, Plant and Equipment [Abstract] Premises and Equipment Property, Plant and Equipment Disclosure [Text Block] Investments in Qualified Affordable Housing Projects Investments in Affordable Housing Projects [Abstract] Amortization expense Amortization Method Qualified Affordable Housing Project Investments, Amortization Tax credits and other tax benefits recognized Affordable Housing Tax Credits and Other Tax Benefits, Amount Schedule of Marketable Securities [Table] Schedule of Marketable Securities [Table] Schedule of Marketable Securities [Table] U.S. government and federal agency US Government Agencies Debt Securities [Member] U.S. government sponsored enterprises US Government-sponsored Enterprises Debt Securities [Member] State and local governments US States and Political Subdivisions Debt Securities [Member] Corporate bonds Corporate Bond Securities [Member] Debt Securities Schedule of Marketable Securities [Line Items] [Line Items] for Schedule of Marketable Securities [Table] [Table] Available-for-sale Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Available-for-sale, Fair Value Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] Less than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 12 Months or More Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Total Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Available-for-sale, Unrealized Loss Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] Less than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 12 Months or Longer Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Held-to-maturity Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position [Abstract] Held-to-maturity, Fair Value Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] Less than 12 Months Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value 12 Months or More Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value Total Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value Held-to-maturity, Unrealized Loss Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] Less than 12 Months Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 12 Months or More Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss Organization, Consolidation and Presentation of Financial Statements [Abstract] Nature of Operations and Summary of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Contingencies and Commitments Commitments and Contingencies Disclosure [Text Block] Loans Receivable Loans and Leases Receivable Disclosure [Abstract] Number of segments in the Company's loan portfolio Financing Receivable, Number of Portfolio Segments Number of portfolio segments in the company's total financing receivables. Variable rate loans Loans Receivable with Variable Rates of Interest Fixed rate loans Loans Receivable with Fixed Rates of Interest Loans pledged as collateral Loans Pledged as Collateral Percentage of consolidated stockholders equity exceeding which no borrower had outstanding loans or commitments Percentage of Consolidated Stockholders Equity Exceeding Which no Borrower had Outstanding Loans or Commitments Percentage of consolidated stockholders equity exceeding which no borrower had outstanding loans or commitments. Loans serviced for others Servicing Asset at Amortized Cost Aggregate amount of loans outstanding to related parties Loans and Leases Receivable, Related Parties New loans to related parties Loans and Leases Receivable, Related Parties, Additions Repayments of loans by related parties Loans and Leases Receivable, Related Parties, Proceeds Effect of changes in composition of related party loans Loans and Leases Receivable Related Parties Change in Composition Loans and Leases Receivable Related Parties Change in Composition Interest income that would have been recorded on non-accrual loans Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans TDR With Pre Modification Loan Balance for Which Oreo Was Received TDR With Pre Modification Loan Balance for Which Oreo Was Received TDR with pre modification loan balance, for which OREO was received. Consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process Mortgage Loans in Process of Foreclosure, Amount OREO Secured by Residential Real Estate Real Estate Acquired Through Foreclosure, Secured by Residential Real Estate Real Estate Acquired Through Foreclosure, Secured by Residential Real Estate Additional unfunded commitments on TDRs Additional Outstanding Commitments on Troubled Debt Restructuring Additional outstanding commitments on TDRs. Charge-offs on TDRs Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down Earnings Per Share [Abstract] Basic and Diluted Earnings Per Share Earnings Per Share Reconciliation [Abstract] Net Income Average outstanding shares - basic Weighted Average Number of Shares Outstanding, Basic Add: dilutive restricted stock awards and stock options Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Average outstanding shares - diluted Weighted Average Number of Shares Outstanding, Diluted Basic earnings per share Earnings Per Share, Basic Diluted earnings per share Earnings Per Share, Diluted Earnings Per Share Earnings Per Share, Diluted, Other Disclosures [Abstract] Restricted stock awards and stock options excluded from the diluted average outstanding share calculation Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Income Tax Examination [Table] Income Tax Examination [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Federal Internal Revenue Service (IRS) [Member] Montana Montana [Member] Montana. Idaho Idaho [Member] Idaho. Utah Utah [Member] Utah. Colorado Colorado [Member] Colorado. Arizona Arizona [Member] Arizona [Member] Income Tax Examination Income Tax Examination [Line Items] Income tax return jurisdictions and years that remain subject to examination Income Tax Examination, Description Earnings Per Share Earnings Per Share [Text Block] Summary of consolidated income tax expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Summary of effective tax rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Summary of net deferred tax asset Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Income tax return jurisdictions and years subject to examination Summary of Income Tax Examinations [Table Text Block] Deposits [Abstract] Deposits Deposits (Textual) [Abstract] Deposits textual. FDIC Insurance limit Cash, FDIC Insured Amount Time deposits that meet or exceed FDIC Insurance limit Time Deposits That Meet or Exceed FDIC Insurance Limit The aggregate amount of domestic time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations that meet or exceed the FDIC Insurance limit. Overdraft demand deposits reclassified as loans Overdraft Demand Deposits Reclassified as Loans Overdraft demand deposits reclassified as loans. Deposits with related parties Related Party Deposit Liabilities General Business Description and Basis of Presentation [Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Debt Securities Marketable Securities, Policy [Policy Text Block] Temporary versus Other-Than-Temporary Impairment Temporary Versus other Than Temporary Impairment [Policy Text Block] Temporary versus other than temporary impairment. Loans Held for Sale Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block] Loans Receivable Finance, Loans and Leases Receivable, Policy [Policy Text Block] Allowance for Loan and Lease Losses Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Premises and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Other Real Estate Owned Finance, Loan and Lease Receivables, Held for Investments, Foreclosed Assets Policy [Policy Text Block] Long-lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Business Combinations and Intangible Assets Goodwill and Intangible Assets, Policy [Policy Text Block] Equity Securities Equity Securities [Policy Text Block] Equity Securities [Policy Text Block] Bank-Owned Life Insurance Bank-Owned Life Insurance Policy [Policy Text Block] Bank-Owned Life Insurance Policy Derivatives and Hedging Activities Derivatives, Policy [Policy Text Block] Revenue Recognition Revenue Recognition, Policy [Policy Text Block] Stock-based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Advertising and Promotion Advertising Cost, Policy, Expensed Advertising Cost [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Comprehensive Income Comprehensive Income, Policy [Policy Text Block] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Accounting Guidance Adopted in 2018 and Pending Adoption at December 31, 2018 New Accounting Pronouncements, Policy [Policy Text Block] Summary of net deferred tax asset Components of Deferred Tax Assets and Liabilities [Abstract] Deferred tax assets Components of Deferred Tax Assets [Abstract] Allowance for loan and lease losses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses Acquisition fair market value adjustments Deferred Tax Assets, Equity Method Investments Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Employee benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Benefits Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Available-for-sale debt securities Deferred Tax Assets, Unrealized Losses on Available-for-Sale Securities, Gross Interest rate swap agreements Deferred Tax Assets, Derivative Instruments Other real estate owned Deferred Tax Assets, Other Real Estate Owned Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from other real estate owned. Other Deferred Tax Assets, Other Total gross deferred tax assets Deferred Tax Assets, Gross Deferred tax liabilities Deferred Tax Liabilities, Gross [Abstract] Intangibles Deferred Tax Liabilities, Intangible Assets Depreciation of premises and equipment Deferred Tax Liabilities, Property, Plant and Equipment Deferred loan costs Deferred Tax Liabilities, Tax Deferred Income FHLB stock dividends Deferred Tax Liabilities Stock Dividends Deferred tax liabilities stock dividends. Debt modification costs Deferred Tax Liabilities, Deferred Expense, Debt Issuance Costs Available-for-sale debt securities Deferred Tax Liabilities, Other Comprehensive Income Other Deferred Tax Liabilities, Other Total gross deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred tax asset Deferred Tax Assets, Net Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Range Minimum [Member] Maximum Range Maximum [Member] Weighted Average Range Weighted Average [Member] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Sales Comparison Approach Valuation, Market Approach [Member] Combined Approach Combined Approach Valuation Technique [Member] Combined Approach [Member] Cost Approach Valuation, Cost Approach [Member] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Selling costs Measurement Input, Cost to Sell [Member] Quantitative Information About Level 3 Fair Value Measurements Fair Value Measurement Inputs and Valuation Techniques [Line Items] Other real estate owned Other Real Estate Owned, Measurement Input Collateral-dependent impaired loans, net of ALLL Impaired Loans, Measurement Input Value of input used to measure impaired loans. Retirement Benefits [Abstract] Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Scheduled maturities of time deposits Scheduled Maturities of Certificates of Deposit [Table Text Block] Scheduled maturities of certificates of deposit. Other Intangible Assets and Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Core Deposit Intangibles Acquired Accumulated impairment charge Goodwill, Impaired, Accumulated Impairment Loss Summary of Interest Rate Swap Derivative Financial Instruments Schedule of Derivative Instruments [Table Text Block] Summary of Pre-Tax Gains or Losses Derivative Instruments, Gain (Loss) [Table Text Block] Offsetting Assets Offsetting Assets [Table Text Block] Offsetting Liabilities Offsetting Liabilities [Table Text Block] Securities Pledged for Repurchase Agreements Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements Lines of credit Line of Credit Facility, Maximum Borrowing Capacity Parent Holding Company Information (Condensed) Condensed Financial Information of Parent Company Only Disclosure [Text Block] Activity within Accumulated Other Comprehensive Loss, Net of Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Document and Entity Information [Abstract] Document and entity information. Entity Registrant Name Entity Registrant Name Trading Symbol Trading Symbol Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Shell Company Entity Shell Company Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Schedule of Gain (Loss) on Securities [Table] Schedule of Gain (Loss) on Securities [Table] Summary of debt securities Gain (Loss) on Securities [Line Items] Available-for-sale Debt Securities, Available-for-sale [Abstract] Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Gross Unrealized Gains Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Total Debt Securities, Available-for-sale Held-to-maturity Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract] Amortized Cost Debt Securities, Held-to-maturity Gross Unrealized Gains Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain Gross Unrealized Losses Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss Fair Value Debt Securities, Held-to-maturity, Fair Value Debt Securities, Available-for-sale and Held-to-maturity [Abstract] Debt Securities, Available-for-sale and Held-to-maturity [Abstract] Amortized Cost Debt Securities, Amortized Cost Basis This item represents the cost of available-for-sale and held-to-maturity debt securities, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. Gross Unrealized Gains Securities, Gross Unrealized Gain Accumulated in Investments Amount of accumulated unrealized gain before deducting unrealized loss on investments in available-for-sale and held-to-maturity securities impacting investments. Gross Unrealized Losses Securities, Gross Unrealized Loss Accumulated in Investments 1 Amount of accumulated unrealized loss before deducting unrealized gain on investments in available-for-sale and held-to-maturity securities impacting investments. Fair Value Debt Securities, Fair Value Fair value of investments in debt securities classified as available-for sale and held-to-maturity. Mortgage-backed securities Collateralized Mortgage Backed Securities [Member] Available-for-Sale Available-for-sale Securities, Debt Maturities [Abstract] Available-for-Sale, Amortized Cost Debt Securities, Available-for-sale, Maturity, Amortized Cost, Rolling Maturity [Abstract] Due within one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Amortized Cost Due after ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost Total before mortgage-backed securities Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost Mortgage-backed securities Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Amortized Cost Available-for-Sale, Fair Value Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract] Due with one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Fair Value Due after ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value Total before mortgage-backed securities Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value Mortgage-backed securities Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Held-to-Maturity Debt Securities, Held-to-maturity, Maturity [Abstract] Held-to-Maturity, Amortized Cost Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract] Due within one year Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost Due after one year through five years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost Due after five years through ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Amortized Cost Due after ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost Total before mortgage-backed securities Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost Mortgage-backed securities Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Amortized Cost Amortized Cost Held-to-Maturity, Fair Value Debt Securities, Held-to-maturity, Maturity, Fair Value, Rolling Maturity [Abstract] Due within one year Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value Due after one year through five years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value Due after five years through ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Fair Value Due after ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value Total before mortgage-backed securities Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value Mortgage-backed securities Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value Total Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Statements of Financial Condition Statement of Financial Position [Abstract] Assets Assets [Abstract] Cash on hand and in banks Cash and Due from Banks Interest bearing cash deposits Interest-bearing Deposits in Banks and Other Financial Institutions Cash and cash equivalents Cash, Cash Equivalents, and Federal Funds Sold Other assets Other Assets Investment in subsidiaries Investments in Subsidiaries Investments in Subsidiaries Total assets Assets Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Dividends payable Subordinated debentures Other liabilities Other Liabilities Total liabilities Liabilities Common stock Common Stock, Value, Outstanding Paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Total stockholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders’ equity Liabilities and Equity Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Condensed Statements of Cash Flows Subsidiary income in excess of dividends distributed Amortization of purchase accounting adjustments Gain on sale of investments Stock-based compensation, net of tax benefits Net change in other assets and other liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash provided by operating activities Net (increase) decrease of premises and equipment Proceeds from sale of non-marketable equity securities Payments for Proceeds from Non Marketable Equity Securities Payments for proceeds from non-marketable equity securities. Equity contribution to subsidiaries Payments to Acquire Additional Interest in Subsidiaries Net cash used in investing activities Net increase in other borrowed funds Tax withholding payments for stock-based compensation Net cash used in financing activities Net increase (decrease) in cash, cash equivalents and restricted cash Carrying amounts of consolidated VIEs' assets and liabilities Schedule of Variable Interest Entities [Table Text Block] Amortization expense and tax credits and other tax benefits recognized for qualified affordable housing project investments Equity Method Investments [Table Text Block] Offsetting Liabilities [Table] Offsetting Liabilities [Table] Offsetting Liabilities [Line Items] Offsetting Liabilities [Line Items] Offsetting Derivative Liabilities Offsetting Derivative Liabilities [Abstract] Gross Amounts of Recognized Liabilities Derivative Liability, Fair Value, Gross Liability Gross Amounts Offset in the Statements of Financial Position Derivative Liability, Fair Value, Gross Asset Net Amounts of Liabilities Presented in the Statements of Financial Position Derivative Liability, Fair Value, Amount Not Offset Against Collateral Statement [Table] Statement [Table] Property, Plant and Equipment by Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Office Buildings Building [Member] Furniture, fixtures and equipment Furniture and Fixtures [Member] Adjustments Due to New Accounting Pronouncements [Axis] Adjustments Due to New Accounting Pronouncements [Axis] Adjustments Due to New Accounting Pronouncements [Axis] Adjustments Due to New Accounting Pronouncements [Domain] Adjustments Due to New Accounting Pronouncements [Domain] Adjustments Due to New Accounting Pronouncements [Domain] Accounting Standards Update 2017-12 Accounting Standards Update 2017-12 [Member] Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] Accounting Standards Update 2017-08 Accounting Standards Update 2017-08 [Member] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] Nature of Operations and Summary of Significant Accounting Policies Statement [Line Items] Number of Bank Divisions Number of Bank Divisions Number of Bank Divisions Number of Operating Segments Number of Operating Segments Maximum Period of Original Maturity to be Included in Cash and Cash Equivalents Maximum Period of Original Maturity to be Included in Cash and Cash Equivalents Maximum Period of Original Maturity to be Included in Cash and Cash Equivalents Federal Reserve Balance or Cash on Hand Required Federal Reserve Balance or Cash on Hand Required Federal Reserve balance or cash on hand required. Minimum Period Past Due to Consider Loans as Delinquent Minimum Period Past Due to Consider Loans as Delinquent Minimum Period Past Due to Consider Loans as Delinquent Minimum Period Past Due to Consider Loans as Non Accrual Minimum Period Past Due to Consider Loans as Non Accrual Minimum Period Past Due to Consider Loans as Non Accrual Number of years for home equity loan origination term Number of years for home equity loan origination term Number of years for home equity loan origination term Number of Quarters Used to Evaluate Historical Loss Experience Financing Receivable, Allowance for Credit Losses, Number of Quarters Used to Evaluate Historical Loss Experience The number of quarters used to evaluate the historical loss experience when determining the general valuation allowance component of the allowance for credit losses. Minimum Number of Days Delinquent to Charge Off Loans Threshold Period Past Due for Write-off of Financing Receivable Useful life of premises and equipment Property, Plant and Equipment, Useful Life Maximum period up to which purchase price of business is allocated to assets acquired and liabilities assumed Maximum Period up to Which Purchase Price of Business is Allocated to Assets Acquired and Liabilities Assumed Maximum Period up to Which Purchase Price of Business is Allocated to Assets Acquired and Liabilities Assumed. Number of Reporting Units Subsequent to Aggregation for Goodwill Assessment Number of Reporting Units Subsequent to Aggregation for Goodwill Assessment Number of Reporting Units Subsequent to Aggregation for Goodwill Assessment Number of steps included in goodwill impairment test Number of steps included in goodwill impairment test Number of steps included in goodwill impairment test Revenue from Contracts with Customers Revenue from Contract with Customer, Including Assessed Tax Impairment losses on receivables related to contracts with customers Capitalized Contract Cost, Accumulated Impairment Percentage of likelihood for term more likely than not as it relates to income taxes Percentage of Likelihood for Term More Likely Than Not Percentage of likelihood for term more likely than not. Number of Steps to Achieve Core Revenue Recognition Principal Number of Steps to Achieve Core Revenue Recognition Principal Number of Steps to Achieve Core Revenue Recognition Principal Effect of cumulative change on retained earnings from applying new accounting pronouncement New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets Effect of cumulative change on assets from applying new accounting pronouncement New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Assets New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Assets Effect of cumulative change on liabilities from applying new accounting pronouncement New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Liabilities New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Liabilities Percentage of Outstanding Common Stock Acquired Business Acquisition, Percentage of Voting Interests Acquired Fair value of consideration transferred Number of Shares Issued for Aquisition Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Loans receivable Business Combination, Acquired Receivable, Fair Value Loans Receivable Acquired, Gross Principal and Contractual Interest Due Business Combination, Acquired Receivables, Gross Contractual Amount Third-party Acquisition Related Costs Business Combination, Acquisition Related Costs Net interest income and non-interest income Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Net income Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Condensed Statements of Financial Condition Condensed Balance Sheet [Table Text Block] Condensed Statements of Operations and Comprehensive Income Condensed Income Statement [Table Text Block] Condensed Statements of Cash Flows Condensed Cash Flow Statement [Table Text Block] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Domain] Other Comprehensive Income Location [Domain] Other Comprehensive Income Other Comprehensive Income (Loss) [Member] Interest Expense Interest Expense [Member] Pre-Tax Gains or Losses Derivative Instruments, Gain (Loss) [Line Items] Amount of gain (loss) recognized in OCI Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Amount of loss reclassified from OCI to interest expense Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net FHLB Advances Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract] Maturing within one year, Amount Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months Maturing within one year, Weighted rate Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due within One Year of Balance Sheet Date Maturing one year through two years, Amount Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two Maturing one year through two years, Weighted rate Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, One to Two Years from Balance Sheet Date Maturing two years through three years, Amount Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three Maturing two years through three years, Weighted rate Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Two to Three Years from Balance Sheet Date Maturing three years through four years, Amount Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Four Maturing three years through four years, Weighted rate Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Three to Four Years from Balance Sheet Date Maturing four years through five years, Amount Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Five Maturing four years through five years, Weighted rate Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Four to Five Years from Balance Sheet Date Thereafter, Amount Federal Home Loan Bank, Advances, Maturities Summary, Due after Year Five