Derivative Instruments and Hedging Activities Disclosure [Abstract] Offsetting Assets [Table] Offsetting Assets [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swaps Interest Rate Swap [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Institutional counterparties Institutional Counterparties [Member] Represents information pertaining to the institutional counterparties. Commercial counterparties Commercial Counterparties [Member] Represents information pertaining to the commercial counterparties. Offsetting Assets [Line Items] Offsetting Assets [Line Items] Offsetting of Financial Assets and Derivative Assets Offsetting Derivative Assets [Abstract] Gross amounts of recognized assets Derivative Asset, Fair Value, Gross Asset Gross amounts offset in the Statements of Condition Derivative Asset, Fair Value, Gross Liability Net amounts of assets presented in the Statements of Condition Derivative Asset Gross amounts not offset in the Statements of Condition, financial instruments Derivative Asset, Not Offset, Policy Election Deduction Gross amounts not offset in the Statements of Condition, cash collateral received Derivative, Collateral, Obligation to Return Cash Net amount Derivative Asset, Fair Value, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election Earnings Per Share [Abstract] EARNINGS PER SHARE Earnings Per Share [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] STOCK-BASED COMPENSATION PLANS Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Receivables [Abstract] Schedule of Financing Receivables Past Due [Table] Schedule of Financing Receivables Past Due [Table] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Commercial Real Estate Commercial Real Estate Portfolio Segment [Member] Commercial and industrial loans Commercial and Industrial Loans Portfolio Segment [Member] Commercial and Industrial Loans Portfolio Segment [Member] Residential Mortgages Residential Portfolio Segment [Member] Consumer Loans Consumer Portfolio Segment [Member] Class of Financing Receivable, Type [Axis] Class of Financing Receivable, Type [Axis] Class of Financing Receivable, Type [Domain] Class of Financing Receivable, Type [Domain] Construction Construction Loans [Member] Other Other Receivable [Member] Class of financing receivables related to other financing receivables. 1-4 family 1 to 4 Family [Member] Class of financing receivables related to 1 to 4 Family financing receivables. Home equity Home Equity Loan [Member] Auto and other Auto And Other Receivable [Member] Class of financing receivables related to auto and other financing receivables. Receivable Type [Axis] Receivable Type [Axis] Receivable [Domain] Receivable [Domain] Business Activities Loans Loans From Business Activities [Member] Represents information pertaining to the loans from business activities. Acquired Loans Loans Acquired From Business Combinations [Member] Represents information pertaining to the loans acquired from business combinations. Acquired Credit Impaired Loans Acquired Credit Impaired Loans [Member] Represents the information pertaining to Acquired credit impaired loans. Non-accrual loans Financing Receivable, Recorded Investment, Past Due [Line Items] Non-accrual loans Financing Receivable, Recorded Investment, Nonaccrual Status Derivative [Table] Derivative [Table] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Total cash flow hedges Cash Flow Hedging [Member] Total economic hedges Economic Hedging [Member] Represents information pertaining to derivatives that are not designated as accounting hedges but are being used as economic hedges. Reverse interest rate swaps Reverse Interest Rate Swaps [Member] Represents information pertaining to the reverse interest rate swaps which can be used to synthetically convert fixed rate debt to floating. Risk participation agreements with dealer banks Risk Participation Agreements [Member] Represents the information pertaining to risk participation agreements with dealer banks. Forward sale commitments Forward Commitments [Member] Represents the forward commitments that are free-standing derivatives which are carried at fair value with changes recorded in the mortgage banking component of noninterest income in the entity's consolidated statements of income. Commitments to lend Commitments to Extend Credit [Member] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] FHLB borrowings Federal Home Loan Bank Borrowings [Member] Tax advantaged economic development bonds Nontaxable Municipal Bonds [Member] Loans with commercial loan customers Commercial Paper [Member] Derivative [Line Items] Derivative [Line Items] Interest rate swap agreements and non-hedging derivative assets and liabilities Derivative Instrument Detail [Abstract] Notional amount Derivative, Notional Amount Weighted average maturity Derivative, Average Remaining Maturity Weighted average rate, received (as percent) Derivative, Weighted Average Rate, Received Represents information pertaining to the derivative weighted average rate which is received. Weighted average rate, contract pay rate (as percent) Derivative, Weighted Average Rate, Paid Represents information pertaining to the derivative weighted average rate which is paid. Estimated fair value asset (liability) Derivative Assets (Liabilities), at Fair Value, Net Debt Disclosure [Abstract] Schedule of Borrowed Funds Schedule of Debt [Table Text Block] Summary of Maturities of FHLBB Advances Schedule of Maturities and Weighted Average Interest Rates of Federal Home Loan Bank Advances [Table Text Block] Tabular disclosure of the contractual maturities and weighted average interest rates on borrowings or advances from Federal Home Loan Bank. Fair Value Disclosures [Abstract] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Non-recurring Fair Value, Measurements, Nonrecurring [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Capitalized servicing rights Capitalized Mortgage Servicing Rights [Member] Represents the details pertaining to capitalized mortgage servicing rights. Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Weighted Average Weighted Average [Member] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Loss severity Measurement Input, Loss Severity [Member] Appraised value Measurement Input, Appraised Value [Member] Constant prepayment rate (CPR) Measurement Input, Constant Prepayment Rate [Member] Discount rate Measurement Input, Discount Rate [Member] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Fair Value of Collateral Fair Value Of Collateral Valuation Technique [Member] Fair value of collateral approach valuation technique used to measure fair value. Discounted Cash Flow Valuation Technique, Discounted Cash Flow [Member] 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 3 Fair Value, Inputs, Level 3 [Member] Quantitative information about the significant unobservable inputs within Level 3 Fair Value Measurement Inputs and Valuation Techniques [Line Items] Impaired loans Impaired Loans, Fair Value Disclosure Represents the amount of impaired loans assets reported on the balance sheet at period end measured at fair value by the entity. Capitalized servicing rights Servicing Asset at Fair Value, Amount Total Assets, Fair Value Disclosure Impaired Financing Receivables, Unobservable Input Impaired Financing Receivables, Measurement Input Impaired Financing Receivables, Measurement Input Servicing Asset, Unobservable Input Servicing Asset, Measurement Input Economic hedges Non-hedging derivatives Nonhedging [Member] Represents information pertaining to derivatives that are not used for hedging purposes and thus are not designated as accounting hedges. Industrial revenue bond Industrial Revenue Bond [Member] Represents information pertaining to the industrial revenue bond, a financing instrument issued by designated local industrial development boards (IDB's) or other issuers authorized by state law. Unrealized gain/(loss) recognized in other non-interest income Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments Favorable (Unfavorable) change in credit valuation adjustment recognized in other non-interest income Derivative Instruments Favorable Changes in Credit Valuation Adjustment Recognized in Other Non Interest Income The favorable changes in credit valuation adjustments on derivative instruments that were recognized in other non-interest income during the current period. Realized gain (loss) in other non-interest income Gain (Loss) on Sale of Derivatives Stockholders' Equity Note [Abstract] CAPITAL RATIOS AND SHAREHOLDERS' EQUITY Stockholders' Equity Note Disclosure [Text Block] Deposits [Abstract] DEPOSITS Deposit Liabilities Disclosures [Text Block] Investments, Debt and Equity Securities [Abstract] Investment Holdings [Table] Investment Holdings [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Municipal bonds and obligations US States and Political Subdivisions Debt Securities [Member] Agency collateralized mortgage obligations Collateralized Debt Obligations [Member] Agency mortgage-backed securities Residential Mortgage Backed Securities [Member] Agency commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Corporate bonds Corporate Bond Securities [Member] Other bonds and obligations Other Debt Obligations [Member] Tax advantaged economic development bonds Tax Advantaged Economic Development Bonds [Member] Represents the information pertaining to the tax advantaged economic development bonds. Investment Holdings [Line Items] Investment Holdings [Line Items] Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] Available for sale securities, less than twelve months, gross unrealized losses Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Available for sale securities, over twelve months, gross unrealized losses Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Available for sale securities, continuous unrealized loss position, accumulated loss Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] Available for sale securities, continuous unrealized loss position, less than twelve months, fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Available for sale securities, continuous unrealized loss position, over twelve months, fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Available for sale securities, continuous unrealized loss position, fair value Debt Securities, Available-for-sale, Unrealized Loss Position Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position [Abstract] Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position [Abstract] Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Held to maturity securities, accumulated unrecognized holding loss Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value Held to maturity securities, accumulated unrecognized holding loss, fair value Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value Securities available for sale and held to maturity Available For Sale Securities and Held To Maturity Securities Continuous Unrealized Loss Position [Abstract] Held to maturity and available for sale securities continuous unrealized loss position, less than twelve months, aggregate losses Debt Securities, Available-for-sale and Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Represents the excess of amortized cost basis over the fair value of securities that have been in a loss position for less than twelve months for those securities that are categorized as held-to-maturity and available-for-sale. Held to maturity and available for sale securities continuous unrealized loss position, less than twelve months, fair value Debt Securities, Available-for-sale and Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months Represents the aggregate fair value of investments in debt and equity securities categorized as held-to-maturity and available-for-sale that have been in a continuous unrealized loss position for less than twelve months. Held to maturity and available for sale securities continuous unrealized loss position, over twelve months, aggregate losses Debt Securities, Available-for-sale and Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Represents the excess of amortized cost basis over the fair value of securities that have been in a loss position for twelve months or longer for those securities that are categorized as held-to-maturity and available-for-sale. Held to maturity and available for sale securities continuous unrealized loss position, over twelve months, fair value Debt Securities, Available-for-sale and Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer Represents the aggregate fair value of investments in debt and equity securities categorized as held-to-maturity and available-for-sale that have been in a continuous unrealized loss position for twelve months or longer. Held to maturity and available for sale securities continuous unrealized loss position, aggregate losses Debt Securities, Available-for-sale and Held-to-maturity, Unrealized Loss Position, Accumulated Loss Represents the excess of amortized cost basis over the fair value of securities that have been in a loss position, which are categorized as held-to-maturity and available-for-sale. Held to maturity and available for sale securities continuous unrealized loss position, fair value Debt Securities, Available-for-sale and Held-to-maturity, Unrealized Loss Position Represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized as held-to-maturity and available-for-sale securities. Organization, Consolidation and Presentation of Financial Statements [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2018-02 Accounting Standards Update 2018-02 [Member] Accounting Standards Update 2018-02 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Reclassification from AOCI Tax Cuts And Jobs Act Of 2017 Reclassification From Aoci To Retained Earnings Tax Effect Tax Cuts And Jobs Act Of 2017 Reclassification From Aoci To Retained Earnings Tax Effect Decrease in retained earnings Retained Earnings (Accumulated Deficit) DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES Derivative Instruments and Hedging Activities Disclosure [Text Block] Revenue from Contract with Customer [Abstract] Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] LOANS Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Net unrealized holding gain (loss) on AFS securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Net unrealized loss on cash flow hedging derivatives Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Net unrealized holding (loss) on pension plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated other comprehensive (loss)/income AOCI Attributable to Parent [Member] Gross changes in each component of accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Balance at Beginning of Period Stockholders' Equity Attributable to Parent Other comprehensive gain before reclassifications OCI, before Reclassifications, Net of Tax, Attributable to Parent Less: amounts reclassified from accumulated other comprehensive income (loss) Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Total other comprehensive (loss)/income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Less: amounts reclassified from accumulated other comprehensive income (loss) related to adoption of ASU 2016-01 and ASU 2018-02 Reclassification From AOCI, Accounting Standards Update, Current Period, Net Of Tax, Attributable To Parent Reclassification From AOCI, Accounting Standards Update, Current Period, Net Of Tax, Attributable To Parent Balance at End of Period Schedule of Actual and Required Capital Ratios Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Schedule of Components of Accumulated Other Comprehensive Income Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Components of Other Comprehensive Income Comprehensive Income (Loss) [Table Text Block] Schedule of Gross Changes in Each Component of Accumulated Other Comprehensive Income Schedule of Changes in Accumulated Other Comprehensive Income (Loss) [Table Text Block] Tabular disclosure of the changes in components of accumulated other comprehensive income (loss). Schedule of Amounts Reclassified Out of Each Component of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Estimated fair values of financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial Assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Trading security Debt Securities, Trading, and Equity Securities, FV-NI Marketable equity securities Equity Securities, FV-NI Securities available for sale Debt Securities, Available-for-sale Securities held to maturity Debt Securities, Held-to-maturity, Fair Value FHLB bank stock and restricted securities Federal Home Loan Bank Stock and Other Restricted Securities at Cost This element represent as Federal Home Loan Bank Stock And Other Restricted Securities. Net loans Loans Receivable, Fair Value Disclosure Loans held for sale Loans Held-for-sale, Fair Value Disclosure Accrued interest receivable Interest Receivable Cash surrender value of bank-owned life insurance policies Cash Surrender Value, Fair Value Disclosure Derivative assets Assets held for sale Disposal Group, Including Discontinued Operation, Assets Financial Liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Total deposits Deposits, Fair Value Disclosure Short-term debt Short-term Debt, Fair Value Long-term Federal Home Loan Bank advances Federal Home Loan Bank Borrowings, Fair Value Disclosure Subordinated borrowings Subordinated Debt Obligations, Fair Value Disclosure Derivative liabilities Derivative Liability, Fair Value, Gross Liability Statement [Table] Statement [Table] ASU 2016-01 Accounting Standards Update 2016-01 [Member] Statement [Line Items] Statement [Line Items] Net unrealized holding gain (loss) Other Comprehensive Income (Loss) before Reclassifications [Abstract] Before Tax OCI, before Reclassifications, before Tax, Attributable to Parent Tax Effect Other Comprehensive Income (Loss) before Reclassifications, Tax Net of Tax Less: reclassification adjustment for gains (losses) realized in net income Reclassification from Accumulated Other Comprehensive Income Current Period [Abstract] Before Tax Reclassification from AOCI, Current Period, before Tax, Attributable to Parent Tax Effect Reclassification from AOCI, Current Period, Tax Net of Tax Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Before Tax Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent Tax Effect Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Less: reclassification related to adoption of ASU Reclassification From AOCI, Accounting Standards Update [Abstract] Reclassification From AOCI, Accounting Standards Update [Abstract] Before Tax Reclassification From AOCI, Accounting Standards Update, Current Period, Before Tax, Attributable To Parent Reclassification From AOCI, Accounting Standards Update, Current Period, Before Tax, Attributable To Parent Tax Effect Reclassification From AOCI, Accounting Standards Update, Current Period, Tax Reclassification From AOCI, Accounting Standards Update, Current Period, Tax Net of Tax Total change to accumulated other comprehensive (loss) AOCI Attributable to Parent [Abstract] Before Tax Total Change To AOCI Before Tax, Attributable To Parent Total Change To AOCI Before Tax, Attributable To Parent Tax Effect Total Change To AOCI Tax, Attributable To Parent Total Change To AOCI Tax, Attributable To Parent Net of Tax Total Change To AOCI Net Of Tax, Attributable To Parent Total Change To AOCI Net Of Tax, Attributable To Parent Fair Value Option, Disclosures [Table] Fair Value Option, Disclosures [Table] Recurring Fair Value, Measurements, Recurring [Member] Loans Held for Sale Loans Held For Sale [Member] Represents the details pertaining to loans held for sale. Loans Held for Sale Fair Value, Option, Quantitative Disclosures [Line Items] Marketable equity securities, fair value Marketable equity securities, amortized cost Equity Securities, FV-NI, Cost Marketable equity securities, gains Equity Securities, FV-NI, Gain (Loss) Marketable equity securities, fair value Available-for-sale Securities, Equity Securities Marketable equity securities, amortized cost Available-for-sale Equity Securities, Amortized Cost Basis Marketable equity securities, gains Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax Aggregate Fair Value Aggregate Unpaid Principal Aggregate Fair Value Less Aggregate Unpaid Principal Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables BORROWED FUNDS Debt Disclosure [Text Block] Banking and Thrift, Interest [Abstract] Schedule of Net Interest Income After Provision for Loan Losses Interest Income and Interest Expense Disclosure [Table Text Block] Net interest income Interest Income (Expense), Net Provision for loan losses Provision for Loan and Lease Losses Net interest income after provision for loan losses Interest Income (Expense), after Provision for Loan Loss Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Pass Pass [Member] Special mention Special Mention [Member] Substandard Substandard [Member] Doubtful Doubtful [Member] Performing Performing Financial Instruments [Member] Nonperforming Nonperforming Financial Instruments [Member] Non Accrual Non Accrual [Member] Represents the category of financing receivables considered to be non-accrual. Classified Classified [Member] Represents the category of financing receivables considered to be classified. Criticized Criticized [Member] Credit quality information Financing Receivable, Recorded Investment [Line Items] Total Loans Loans and Leases Receivable, Net of Deferred Income SECURITIES AVAILABLE FOR SALE, HELD TO MATURITY, AND MARKETABLE EQUITY SECURITIES Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Document and Entity Information Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Other accumulated comprehensive income (loss), before tax AOCI before Tax, Attributable to Parent Income taxes related to items of accumulated other comprehensive income AOCI Tax, Attributable to Parent Total shareholders’ equity Amortized cost Debt Securities, Trading, Amortized Cost Trading security, at fair value Debt Securities, Trading Statement of Cash Flows [Abstract] Cash flows from 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] Net amortization of securities Accretion (Amortization) of Discounts and Premiums, Investments Change in unamortized net loan costs and premiums Change in Unamortized Net Loan Costs and Premiums This element represent as Change In Unamortized Net Loan Costs And Premiums. Premises and equipment depreciation and amortization expense Depreciation, Depletion and Amortization, Nonproduction Stock-based compensation expense Share-based Compensation Accretion of purchase accounting entries, net Amortization Amortization of other intangibles Amortization of Intangible Assets Write down of other real estate owned Impairment of Real Estate Income from cash surrender value of bank-owned life insurance policies Bank Owned Life Insurance Income Securities losses (gains), net Marketable Securities, Realized Gain (Loss) Originations of loans held for sale Increase (Decrease) in Loans Held-for-sale Proceeds from sale of loans held for sale Proceeds from Sale of Loans Held-for-sale Net gain on sale of loans and other mortgage banking income Gain (Loss) In Change Of Fair Value Of Loans Held For Sale Gain (Loss) In Change Of Fair Value Of Loans Held For Sale Loss on disposition of assets Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Gain on sale of real estate Gains (Losses) on Sales of Other Real Estate Amortization of interest in tax-advantaged projects Amortization of Tax Credits Represent the information pertaining to amortization of tax credits Net change in other Other Noncash Income (Expense) Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Net decrease in trading security Increase (Decrease) in Debt Securities, Trading, and Equity Securities, FV-NI Proceeds from sales of securities available for sale Proceeds from Sale of Available-for-sale Securities Proceeds from maturities, calls, and prepayments of securities available for sale Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Purchases of securities available for sale Payments to Acquire Available-for-sale Securities Proceeds from sales of marketable equity securities Proceeds from Sale of Available-for-sale Securities, Equity Purchases of marketable equity securities Payments to Acquire Available-for-sale Securities, Equity Proceeds from maturities, calls, and prepayments of securities held to maturity Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Purchases of securities held to maturity Payments to Acquire Held-to-maturity Securities Net change in loans Payments for (Proceeds from) Loans and Leases Purchases of bank owned life insurance Payment to Acquire Life Insurance Policy, Investing Activities Proceeds from surrender of bank-owned life insurance Proceeds from Life Insurance Policy Proceeds from sale of Federal Home Loan Bank stock Proceeds from Sale of Federal Reserve Bank Stock Purchase of Federal Home Loan Bank stock Payments to Acquire Federal Reserve Bank Stock Net investment in limited partnership tax credits Payments for (Proceeds from) Other Investing Activities Purchase of premises and equipment, net Payments to Acquire Property, Plant, and Equipment Payment to terminate cash flow hedges Payments for (Proceeds from) Derivative Instrument, Investing Activities Proceeds from sale of other real estate Proceeds from Sale of Other Real Estate Net cash (used) by investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Net increase in deposits Increase (Decrease) in Deposits Proceeds from Federal Home Loan Bank advances and other borrowings Proceeds from Issuance of Long-term Debt Repayments of Federal Home Loan Bank advances and other borrowings Repayments of Long-term Debt Exercise of stock options Proceeds from Stock Options Exercised Common and preferred stock cash dividends paid Payments of Ordinary Dividends, Common Stock Common stock issued, net Proceeds from Issuance of Common Stock Acquisition contingent consideration paid Payment for Contingent Consideration Liability, Financing Activities Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value, Including Discontinued Operations Cash and cash equivalents at end of period Supplemental cash flow information: Supplemental Cash Flow Information [Abstract] Interest paid on deposits Interest Paid on Deposits This element represent as Interest Paid On Deposits. Interest paid on borrowed funds Interest Paid, Excluding Capitalized Interest, Operating Activities Income taxes paid (refund), net Income Taxes Paid, Net Other non-cash changes: Other Noncash Investing and Financing Items [Abstract] Other net comprehensive income Real estate owned acquired in settlement of loans Real Estate Owned Acquired in Settlement of Loans Represents the value of real estate acquired in settlement of loans through non cash transactions. Basis of Presentation Consolidation, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Prior Period Acquisition Business Combinations Policy [Policy Text Block] Recently Adopted Accounting Principles and Future Application of Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Revenue Revenue Recognition, Policy [Policy Text Block] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Commercial real estate Residential mortgages Consumer Allowance for loan losses Financing Receivable, Allowance for Credit Losses [Line Items] Activity in the allowance for loan losses Allowance for Loan and Lease Losses [Roll Forward] Balance at beginning of period Loans and Leases Receivable, Allowance Charged-off loans Allowance for Loan and Lease Losses, Write-offs Recoveries on charged-off loans Allowance for Loan and Lease Loss, Recovery of Bad Debts Provision/(releases) for loan losses Balance at end of period Individually evaluated for impairment Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment Collectively evaluated for impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment Total Schedule of Loans Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Schedule of Activity in the Accretable Yield for the Acquired Loan Portfolio that Falls Under the Review of ASC 310-30, Accounting for Certain Loans or Debt Securities Acquired in a Transfer Schedule of Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Accretable Yield Movement [Table Text Block] Tabular disclosure of changes in accretable yield for purchased credit impaired finance receivables by way of additions, accretion, reclassifications and disposals during the period. Summary of Past Due Loans Past Due Financing Receivables [Table Text Block] Summary of Information Pertaining to Non-Accrual Loans Schedule of Financing Receivables, Non Accrual Status [Table Text Block] Schedule of Loans Evaluated for Impairment Schedule of Loans Evaluated for Impairment [Table Text Block] Tabular disclosure related to loans evaluated for impairment. Summary of Impaired Loans Impaired Financing Receivables [Table Text Block] Summary of the Average Recorded Investment and Interest Income Recognized on Impaired Loans Impaired Financing Receivables Average Balances and Related Interest Income Recognized [Table Text Block] Tabular disclosure of average recorded investment in impaired loans and related interest income recognized for the periods indicated. Schedule of Recorded Investment and Number of Modifications for TDRs Identified During the Period Troubled Debt Restructurings on Financing Receivables [Table Text Block] Schedule of TDR Activity Financing Receivable Troubled Debt Restructuring Activity [Table Text Block] Tabular disclosure of activity of troubled debt restructuring financial receivables. Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Non-Vested Stock Awards Outstanding Restricted Stock [Member] Stock Options Outstanding Employee Stock Option [Member] Stock-based compensation plans Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Non-vested Stock Awards Outstanding, Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Balance at the beginning of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Stock awards vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Balance at the end of the period (in shares) Non-vested Stock Awards Outstanding, Weighted-Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Balance at the beginning of the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Stock awards vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Balance at the end of the period (in dollars per share) Stock Options Outstanding, Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Balance at the beginning of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Stock options exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Balance at the end of the period (in shares) Exercisable options at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Stock Options Outstanding, Weighted-Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Balance at the beginning of the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Stock options exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Expired (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Balance at the end of the period (in dollars per share) Exercisable options at the end of the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Total Fair Value Debt securities Debt Securities [Member] Marketable equity securities Equity Securities [Member] Agency collateralized mortgage obligations Collateralized Mortgage Obligations [Member] Agency residential mortgage-backed securities Trust preferred securities Trust Preferred Securities Subject to Mandatory Redemption [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] Trading security Securities available for sale Capitalized servicing rights 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] Commerce Commerce Bancshares Corporation [Member] Commerce Bancshares Corporation [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common stock Common Stock [Member] Preferred stock Preferred Stock [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Company stock issued to Commerce common shareholders Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Cash in lieu paid to Commerce shareholders Payments to Acquire Businesses, Gross Total consideration paid Business Combination, Consideration Transferred Recognized amounts of identifiable assets acquired and (liabilities) assumed, at fair value: Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract] Cash and short-term investments Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Short-term Investments Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Short-term Investments Cash and short-term investments, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Cash and Short-term Investments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Cash and Short-term Investments Investment securities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities Investment securities, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Marketable Securities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Marketable Securities Loans, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets Loans, net, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets Premises and equipment Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Premises and equipment, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment Core deposit intangibles Business Combinations, Recognized Identifiable Assets Acquired and Liabilities Assumed, Core Deposit Intangibles Business Combinations, Recognized Identifiable Assets Acquired and Liabilities Assumed, Core Deposit Intangibles Core deposit intangibles, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Core Deposit Intangibles Business Combination, Provisional Information, Initial Accounting Incomplete, Core Deposit Intangibles Deferred tax assets, net Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Deferred tax assets, net, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Deferred Tax Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Deferred Tax Assets Goodwill and other intangibles Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Goodwill And Other Intangibles Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Goodwill And Other Intangibles Goodwill and other intangibles, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Goodwill and Other Intangible Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Goodwill and Other Intangible Assets Other assets Business Combinations, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets Business Combinations, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets Other assets, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Assets Deposits Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits Deposits, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deposits Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deposits Borrowings Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Borrowings, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Long-term Debt Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Long-term Debt Other liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Assumed Other liabilities, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Liabilities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Liabilities Total identifiable net assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Total identifiable net assets, fair value adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets and Liabilities, Net Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets and Liabilities, Net Goodwill Goodwill Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] 1-4 Family Impaired loans Financing Receivable, Impaired [Line Items] Recorded Investment Impaired Financing Receivable, Recorded Investment [Abstract] With no related allowance Impaired Financing Receivable, with No Related Allowance, Recorded Investment With an allowance recorded Impaired Financing Receivable, with Related Allowance, Recorded Investment Total Impaired Financing Receivable, Recorded Investment Unpaid Principal Balance Impaired Financing Receivable, Unpaid Principal Balance [Abstract] With no related allowance Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance With an allowance recorded Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance Total Impaired Financing Receivable, Unpaid Principal Balance Related Allowance Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] With an allowance recorded Impaired Financing Receivable, Related Allowance Debt securities: Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] Available-for-sale debt securities, amortized cost basis Debt Securities, Available-for-sale, Amortized Cost Available-for-sale debt securities, accumulated gross unrealized gain Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Available-for-sale debt securities, accumulated gross unrealized loss Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Available-for-sale securities, debt securities Securities held to maturity Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract] Held to maturity, amortized cost basis Debt Securities, Held-to-maturity Held to maturity securities accumulated unrecognized holding gains Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain Held to maturity securities, accumulated unrecognized holding loss Securities held to maturity, fair value Marketable equity securities, gross unrealized gains Equity Securities, FV-NI, Unrealized Gain Marketable equity securities, gross unrealized losses Equity Securities, FV-NI, Unrealized Loss Total, amortized cost basis Debt Securities, Available-for-sale and Held-to-maturity, and Equity Securities, FV-NI, Amortized Cost Represents the cost of debt and equity securities, which are categorized as held-to-maturity and available-for-sale, 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. Total, gross unrealized gain Debt Securities, Available-for-sale and Held-to-maturity, and Equity Securities, FV-NI, Accumulated Gross Unrealized Gain, before Tax Represents the gross unrealized gains for securities, at a point in time, which are categorized as held-to-maturity and available-for-sale securities. Total, gross unrealized loss Debt Securities, Available-for-sale and Held-to-maturity, and Equity Securities, FV-NI, Accumulated Gross Unrealized Loss, before Tax Represents the gross unrealized losses for securities, at a point in time, which are categorized as held-to-maturity and available-for-sale securities. Total, fair value Debt Securities, Available-for-sale and Held-to-maturity, and Equity Securities, FV-NI Debt Securities, Available-for-sale and Held-to-maturity, and Equity Securities, FV-NI 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] Fixed rate advances Federal Home Loan Bank Fixed Rate Advances [Member] Fixed rate borrowings from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and also in times of liquidity shortages. Debt Instrument [Line Items] Debt Instrument [Line Items] Principal Federal Home Loan Bank, Advances, Rolling Maturity [Abstract] 2018 Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Rolling Twelve Months 2019 Federal Home Loan Bank, Advances, Maturities Summary, Due in Rolling Year Two 2020 Federal Home Loan Bank, Advances, Maturities Summary, Due in Rolling Year Three 2021 Federal Home Loan Bank, Advances, Maturities Summary, Due in Rolling Year Four 2022 and beyond Federal Home Loan Bank, Advances, Maturities Summary, Due after Rolling Year Four Amount of advances from Federal Home Loan Bank (FHLBank) maturing after the fourth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Total FHLB advances Advances from Federal Home Loan Banks Weighted Average Rate (as a percent) Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due [Abstract] 2018 Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due within One Year of Balance Sheet Date 2019 Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, One to Two Years from Balance Sheet Date 2020 Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Two to Three Years from Balance Sheet Date 2021 Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Three to Four Years from Balance Sheet Date 2022 and beyond Federal Home Loan Bank Advances Maturities Summary Average Interest Rate of Amounts Due after Four Years of Balance Sheet Date The weighted average interest rate applicable to the Federal Home Loan Bank advances maturing after the fourth fiscal year following the latest fiscal year. Total FHLB advances Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Interest Rate at Period End Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Bank Subsidiaries [Member] Tier 1 capital to risk-weighted assets Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Total capital to risk weighted assets Capital to Risk Weighted Assets Common equity tier 1 capital to risk weighted assets Common Equity Tier One Risk Based Capital to Risk Weighted Assets Common equity Tier 1 capital divided by risk weighted assets as defined by regulations. Tier 1 capital to risk weighted assets Tier One Risk Based Capital to Risk Weighted Assets Tier 1 capital to average assets Tier One Leverage Capital to Average Assets Regulatory minimum to be well capitalized, Total capital to risk weighted assets (as percent) Capital Required to be Well Capitalized to Risk Weighted Assets Regulatory minimum to be well capitalized, Common equity tier 1 capital to risk weighted assets (as percent) Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets The Common equity Tier 1 capital ratio (Common equity Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. Regulatory minimum to be well capitalized, Tier 1 capital to risk weighted assets (as percent) Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Regulatory minimum to be well capitalized, Tier 1 capital to average assets (as percent) Tier One Leverage Capital Required to be Well Capitalized to Average Assets Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Unvested stock award shares Stock options Anti-dilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Securities excluded from the earnings per share calculations (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Forward commitments Forward Contracts [Member] Commitments to lend Historical Trend Historical Trend Valuation Technique [Member] Historical trend approach valuation technique used to measure fair value. Pricing Model Pricing Model Valuation Technique [Member] Pricing model approach valuation technique used to measure fair value. Closing Ratio Measurement Input, Closing Ratio [Member] Measurement Input, Closing Ratio [Member] Origination Costs, per loan Measurement Input, Origination Costs [Member] Measurement Input, Origination Costs [Member] Trading security Derivative Asset Servicing Asset Servicing Asset Total Fair Value, Net Asset (Liability) Trading Security, Significant Unobservable Input Debt Securities, Trading, Measurement Input Derivative Asset. Significant Unobservable Input Derivative Asset, Measurement Input Servicing Asset, Significant Unobservable Input Summary of securities available for sale (AFS) and held to maturity Marketable Securities [Table Text Block] Schedule of amortized cost and estimated fair value of available for sale (AFS) and held to maturity (HTM) securities, segregated by contractual maturity Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of securities with unrealized losses, segregated by the duration of their continuous unrealized loss positions Schedule of Unrealized Loss on Investments [Table Text Block] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Commercial loans Commercial Portfolio Segment [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Schedule of Interest Rate Swap Agreements and Non-Hedging Derivative Assets and Liabilities Schedule of Derivative Instruments [Table Text Block] Schedule of Amounts Included in the Consolidated Statements of Income and in the Other Comprehensive Income Section of the Consolidated Statements of Comprehensive Income Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Amounts Included in the Consolidated Statements of Income Related to Economic Hedges and Non-Hedging Derivatives Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of Assets Subject to an Enforceable Master Netting Arrangement Offsetting Assets [Table Text Block] Schedule of Liabilities Subject to an Enforceable Master Netting Arrangement Offsetting Liabilities [Table Text Block] Advances from the FHLB Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] Subordinated borrowings Private Placement Subordinated Notes [Member] Represents information pertaining to the private placement fixed and floating rate junior subordinated notes. Junior subordinated borrowings Junior Subordinated Debt [Member] Short-term borrowings Short-term Debt Long-term borrowings Long-term Debt Total borrowings Debt and Capital Lease Obligations Weighted average rate on short-term borrowings (as percent) Short-term Debt, Weighted Average Interest Rate, at Point in Time Weighted average rate on long-term borrowings (as percent) Long-term Debt, Weighted Average Interest Rate, at Point in Time Weighted average rate (as percent) Debt, Weighted Average Interest Rate FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] Loans receivable: balance at end of period Loans and Leases Receivable, Other Information [Abstract] Individually evaluated for impairment Financing Receivable, Individually Evaluated for Impairment Purchased credit-impaired loans Financing Receivable, Purchased Credit-Impaired Loans Financing Receivable, Purchased Credit-Impaired Loans Collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Impairment Total loans Schedule of Activity in the Allowance for Loan Losses Allowance for Credit Losses on Financing Receivables [Table Text Block] Schedule of Loans by Risk Rating Financing Receivable Credit Quality Indicators [Table Text Block] Summary of Information About Total Loans Rated Special Mention or Lower Schedule of Financing Receivable Rated Special Mention or Lower [Table Text Block] Tabular disclosure of financing receivables, rated as special mention or lower. Income Statement [Abstract] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Mortgage banking originations Mortgage Banking [Member] Loan related income Bank Servicing [Member] Deposit related fees Deposit Account [Member] Insurance commissions and fees Insurance Revenue [Member] Insurance Revenue [Member] Wealth management fees Asset Management Fees [Member] Asset Management Fees [Member] Total fee income Banking [Member] Interest and dividend income Interest and Dividend Income, Operating [Abstract] Loans Interest and Fee Income, Loans and Leases Securities and other Interest and Dividend Income, Securities, Operating Total interest and dividend income Interest and Dividend Income, Operating Interest expense Interest Expense [Abstract] Deposits Interest Expense, Deposits Borrowings Interest Expense, Borrowings Total interest expense Interest Expense Net interest income Non-interest income Noninterest Income [Abstract] Other, net Noninterest Income, Other Gain/(loss) on securities, net Debt and Equity Securities, Gain (Loss) Gain on sale of business operations and other assets, net Gain (Loss) on Disposition of Business Loss on termination of hedges Gain Loss on Termination of Derivative Instruments Designated as Hedging Instruments Represents the amount of gain (loss) recorded during the reporting period related to termination of hedging derivative instruments. Total non-interest income Noninterest Income Total net revenue Revenues Non-interest expense Noninterest Expense [Abstract] Compensation and benefits Labor and Related Expense Occupancy and equipment Occupancy and Equipment This element represent as Occupancy And Equipment. Technology and communications Communications and Information Technology Marketing and promotion Marketing Expense Professional services Professional Fees FDIC premiums and assessments Federal Deposit Insurance Corporation Premium Expense Other real estate owned and foreclosures Other Real Estate Owned This element represent as Other Real Estate Owned. Amortization of intangible assets Acquisition, restructuring, and other expenses Other Nonrecurring Expense Other Other Noninterest Expense Total non-interest expense Noninterest Expense Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Net income Preferred stock dividend Preferred Stock Dividends, Income Statement Impact Income available to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Earnings per common share: Earnings Per Share, Basic and Diluted [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Weighted average shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Schedule of Earnings Per Share Basic and Diluted [Table] Schedule of Earnings Per Share Basic and Diluted [Table] Disclosure pertaining to the entity's basic and diluted earnings per share. Earnings per share Earnings Per Share Basic and Diluted [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Average number of common shares issued (in shares) Weighted Average Number of Shares Issued, Basic Less: average number of treasury shares (in shares) Weighted Average Number of Shares, Treasury Stock Less: average number of unvested stock award shares (in shares) Weighted Average Number of Shares, Restricted Stock Plus: average participating preferred shares (in shares) Weighted Average Number of Shares Outstanding, Preferred Stock Weighted Average Number of Shares Outstanding, Preferred Stock Average number of basic common shares outstanding (in shares) Plus: dilutive effect of share-based payment arrangements (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Average number of diluted common shares outstanding (in shares) LOAN LOSS ALLOWANCE Allowance for Credit Losses [Text Block] Summary of Time Deposits Schedule of Time Deposits [Table Text Block] Tabular disclosure of deposits that cannot be withdrawn before a set date without penalty or for which notice of withdrawal is required. Time deposits include, but are not limited to, certificates of deposits, individual retirement accounts and open accounts. Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Number of trading securities in the portfolio (security) Investment Portfolio Number of Securities Represents the number of securities in the entity's security portfolio. Gains (losses) in fair value of loans held for sale included in earnings Fair Value, Option, Changes in Fair Value, Gain (Loss) Junior subordinated debentures re-price period (in days) Junior Subordinated Debentures Re-price Period Represents the re-price period of junior subordinated debentures. Number of Modifications Financing Receivable, Modifications, Number of Contracts Pre-Modification Outstanding Recorded Investment Financing Receivable, Modifications, Pre-Modification Recorded Investment Post-Modification Outstanding Recorded Investment Financing Receivable, Modifications, Post-Modification Recorded Investment Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Table] Realized gains on AFS securities: Realized (losses) on cash flow hedging derivatives: Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Amount Reclassified From Accumulated Other Comprehensive Income (loss) Reclassification out of Accumulated Other Comprehensive Income [Member] Amounts reclassified out of each component of accumulated other comprehensive income Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Non-interest income Interest expense Non-interest expense Tax (expense) benefit REVENUE Revenue from Contract with Customer [Text Block] Cash flow hedges Accumulated net gain (loss) from cash flow hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] Cash collateral pledged Derivative, Collateral, Right to Reclaim Cash Amortized cost of securities pledged as collateral to derivative counterparties Derivative Securities Pledged as Collateral Amortized Cost Represents the amortized cost of securities that are pledged as collateral to the derivative counterparties. Fair value of securities as pledged collateral to derivative counterparties Financial Instruments, Owned and Pledged as Collateral, at Fair Value Number of instruments (contract) Derivative, Number of Instruments Held Durations of derivative instruments (in years) Derivative, Term of Contract Interest expense Amount of ineffectiveness Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness Fixed rate of interest (as percent) Derivative, Fixed Interest Rate Maturity period (in years) Debt Instrument, Term Credit valuation adjustments Derivative, Credit Risk Valuation Adjustment Derivative Assets (Liabilities) Net Amount of credit risk valuation adjustments to the net of derivative assets (derivative liabilities) to properly reflect the credit quality of the counterparties. Net asset position Derivative Asset, Fair Value, Amount Offset Against Collateral Derivative liability Derivative Liability Amount of collateral posted for the net liability positions Collateral Already Posted, Aggregate Fair Value Offsetting Liabilities [Table] Offsetting Liabilities [Table] Offsetting Liabilities [Line Items] Offsetting Liabilities [Line Items] Offsetting of Financial Liabilities and Derivative Liabilities Offsetting Derivative Liabilities [Abstract] Gross amounts of recognized liabilities Gross amounts offset in the Statements of Condition Derivative Liability, Fair Value, Gross Asset Net amounts of liabilities presented in the Statements of Condition Gross amounts not offset in the Statements of Condition, financial instruments Derivative Liability, Not Offset, Policy Election Deduction Gross amounts not offset in the Statements of Condition, cash collateral pledged Net amount Derivative Liability, Fair Value, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES Interest Income and Interest Expense Disclosure [Text Block] Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward] Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward] Balance at beginning of period Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Accretion Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion Net reclassifications from (to) nonaccretable difference Certain Loans Acquired in Transfer not Accounted for as Debt Securities Changes in Cash Flow not Affecting Nonaccretable Difference Certain Loans Acquired in Transfer not Accounted for as Debt Securities Changes in Cash Flow not Affecting Nonaccretable Difference Payments received, net Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Payments Received Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Payments Received Disposals Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Disposals of Loans Balance at end of period Statement of Financial Position [Abstract] Series B Convertible Preferred Stock Convertible Preferred Stock [Member] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Treasury stock (in shares) Treasury Stock, Shares Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Stock awards vested (in shares) Total compensation cost Allocated Share-based Compensation Expense Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Interest Expense Interest Expense [Member] Other non-interest expense Other Non-interest Expense [Member] Other Non-interest Expense [Member] Unrealized (loss) recognized in accumulated other comprehensive loss Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss) Less: reclassification of unrealized (loss) from accumulated other comprehensive income to interest expense Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Net tax (expense) benefit on items recognized in accumulated other comprehensive income Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Other comprehensive gain (loss) recorded in accumulated other comprehensive income, net of reclassification adjustments and tax effects Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Summary of fair values of acquired assets, liabilities assumed, and goodwill Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Assets Assets [Abstract] Cash and due from banks Cash and Due from Banks Short-term investments Cash Equivalents, at Carrying Value Total cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Marketable equity securities, at fair value Marketable Securities Securities available for sale, at fair value Available-for-sale Securities Securities held to maturity (fair values of $371,775 and $405,276) Federal Home Loan Bank stock and other restricted securities Total securities Investments Loans held for sale, at fair value Loans Receivable Held-for-sale, Net, Not Part of Disposal Group or Discontinued Operation Amount of loans held for sale, including but not limited to, commercial and consumer loans. Excludes loans not part of a disposal group or discontinued operation. Commercial real estate loans Loans Receivable, Gross, Commercial, Real Estate Commercial and industrial loans Loans Receivable, Gross, Commercial and Industrial Residential mortgages Loans and Leases Receivable, Gross, Consumer, Mortgage Consumer loans Loans and Leases Receivable, Gross, Consumer, Real Estate Less: Allowance for loan losses Net loans Loans and Leases Receivable, Net Amount Premises and equipment, net Property, Plant and Equipment, Net Other intangible assets Intangible Assets, Net (Excluding Goodwill) Cash surrender value of bank-owned life insurance policies Bank Owned Life Insurance Deferred tax assets, net Deferred Tax Assets, Net Other assets Other Assets Total assets Assets Liabilities Liabilities [Abstract] Demand deposits Demand Deposit Accounts NOW and other deposits Deposits, Negotiable Order of Withdrawal (NOW) Money market deposits Deposits, Money Market Deposits Savings deposits Deposits, Savings Deposits Time deposits Time Deposits Total deposits Deposits Short-term debt Long-term Federal Home Loan Bank advances Long-term Federal Home Loan Bank Advances Subordinated borrowings Junior Subordinated Notes Other liabilities Other Liabilities Total liabilities Liabilities Shareholders’ equity Stockholders' Equity Attributable to Parent [Abstract] Preferred Stock (Series B non-voting convertible preferred stock - $0.01 par value; 2,000,000 shares authorized, 521,607 shares issued and outstanding in 2018; 1,000,000 shares authorized, 521,607 shares issued and outstanding in 2017 Preferred Stock, Value, Issued Common stock ($.01 par value; 100,000,000 shares authorized and 46,211,894 shares issued and 45,420,478 shares outstanding in 2018; 50,000,000 shares authorized, 46,211,894 shares issued and 45,290,433 shares outstanding in 2017) Common Stock, Value, Issued Additional paid-in capital - common stock Additional Paid in Capital, Common Stock Unearned compensation Deferred Compensation Equity Retained earnings Accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury stock, at cost (791,416 shares in 2018 and 921,461 shares in 2017) Treasury Stock, Value Total liabilities and shareholders’ equity Liabilities and Equity Summary of Activity in the Stock Award and Stock Option Plans Share-based Compensation, Activity [Table Text Block] Statement of Stockholders' Equity [Abstract] Common stock, cash dividends declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Preferred stock, cash dividends declared (in dollars per share) Preferred Stock, Dividends Per Share, Declared Advances from the FHLB Federal Reserve Bank Advances Federal Reserve Bank Advances [Member] Federal Home Loan Bank Certificates And Obligations F H L B Amortizing Advances Federal Home Loan Bank Certificates And Obligations F H L B Amortizing Advances [Member] Represents information pertaining to federal home loan bank (FHLB) amortizing advances. Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Three-month LIBOR rate Debt Instrument Variable Rate Three Month L I B O R [Member] Represents the three-month London Interbank Offered Rate used to calculate the variable interest rate of the debt instrument. LIBOR London Interbank Offered Rate (LIBOR) [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Trust I Berkshire Hills Capital Trust I [Member] Represents information pertaining to Berkshire Hills Capital Trust I. Line of credit, current Line of Credit, Current Long-term line of credit Long-term Line of Credit Principal amount of debt issued Debt Instrument, Face Amount Discount rate (as a percent) Debt Instrument, Issuance Discount Rate Represents the discount rate at the issuance of the debt instrument. Fixed interest rate (as percent)