ELTIP Executive Long-Term Incentive Share Plan [Member] Executive Long-Term Incentive Share Plan [Member] Total amortized cost Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process Offsetting Liabilities [Line Items] Offsetting Liabilities [Line Items] Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Short-Term Investments and Investments Investment, Policy [Policy Text Block] Channel Islands and the UK Channel Islands And United Kingdom Segment [Member] Channel Islands And United Kingdom Segment [Member] Accrued interest and other liabilities Other liabilities, including accrued interest and payables to subsidiaries Other Liabilities, Miscellaneous Other Liabilities, Miscellaneous Appreciation / (depreciation) Changes Measurement [Member] Entity Listings, Exchange [Axis] Entity Listings, Exchange [Axis] Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Schedule of expected benefit payments Schedule of Expected Benefit Payments [Table Text Block] Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Additional paid-in capital Additional Paid-in Capital [Member] EDIP and ELTIP Employee Deferred Incentive Plan and Executive Long-Term Incentive Share Plan [Member] Employee Deferred Incentive Plan and Executive Long-Term Incentive Share Plan [Member] Tabular List, Table Tabular List [Table Text Block] Target allocation Defined Benefit Plan, Plan Assets, Target Allocation, Percentage Weighted average number of common shares held as treasury stock (in shares) Weighted Average Number of Shares, Treasury Stock New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Short-term investments other than restricted cash: purchases Payments to Acquire Short-Term Investments Schedule of related party transactions Schedule of Related Party Transactions [Table Text Block] Unrecognized Share-based Compensation Cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount [Abstract] Goodwill [Line Items] Goodwill [Line Items] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Measurement Basis [Axis] Measurement Basis [Axis] 2027 Other Commitment, to be Paid, Year Two Adjustment to Compensation: Adjustment to Compensation [Axis] Held-to-maturity securities with unrealized losses, 12 months or more, Fair value Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value Related party transactions Related Party Transactions Disclosure [Text Block] Overdrafts Overdraft Loan [Member] Overdraft Loan [Member] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] Restricted Stock and Performance Shares Restricted Stock and Performance Shares [Member] Restricted Stock and Performance Shares Net assets of subsidiaries Investments In Subsidiaries Investments In Subsidiaries Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Recoveries of previous charge-offs Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery Stock, Class of Stock [Table] Stock, Class of Stock [Table] Cash and Portfolio Secured Lending Collateral Cash And Portfolio Secured Lending Collateral [Member] Cash And Portfolio Secured Lending Collateral Schedule of cash and cash equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Current tax expense Current Income Tax Expense (Benefit) 1 to 5 years Debt Securities, Held-to-Maturity, Amortized Cost Excluding Accrued Interest, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year One through Five Prior year tax adjustments Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount Adjustment to Compensation, Amount Adjustment to Compensation Amount Pension plans Defined benefit pension plan Pension Plan [Member] (Increase) decrease in accrued interest receivable and other assets Increase (Decrease) in Other Operating Assets Basis of Consolidation Consolidation, Policy [Policy Text Block] Share-based payments and settlements Share-Based Payment Arrangement, Noncash Expense Notional  amounts  Derivative Asset, Notional Amount Income tax benefit (expense) Federal Income Tax Expense (Benefit), Continuing Operations Operating Lease Income Comprehensive Income Extensible List Not Disclosed Flag OperatingLeaseIncomeComprehensiveIncomeExtensibleListNotDisclosedFlag Operating Lease Income Comprehensive Income Extensible List Not Disclosed Flag Government Government Sector [Member] Employee stock option Share-Based Payment Arrangement, Option [Member] 2031 & thereafter Contractual Obligation, to be Paid, after Year Five Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Cash and Cash Equivalents and Consolidated Statements of Cash Flows Cash and Cash Equivalents, Policy [Policy Text Block] % Effective Income Tax Rate Reconciliation, Percent [Abstract] Net prior service credit (cost) Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax Short-term investments Cash, Cash Equivalent, and Short-Term Investment [Text Block] Fair value of awards vested Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested Property Occupancy, Net, Adjusted Occupancy, Net, Adjusted Common share cash dividends declared and paid, $1.88 per share (2024: $1.76 per share) Dividends, Common Stock, Cash Total shareholders’ equity Balance at beginning of year Balance at end of year Total shareholders’ equity Equity, Attributable to Parent Measurement Frequency [Axis] Measurement Frequency [Axis] 5 to 10 years Debt Securities, Held-to-Maturity, Amortized Cost Excluding Accrued Interest, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year 5 through 10 Schedule of Available-for-sale Securities [Table] Debt Securities, Available-for-Sale [Table] Insider Trading Policies and Procedures [Line Items] Schedule of premise, equipment, and computer software Property, Plant and Equipment [Table Text Block] Common shares, authorized (in shares) Common Stock, Shares Authorized Financial assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Issuance of common shares (in shares) Stock Issued During Period, Shares, New Issues Fair Value, Measurements, Recurring Fair Value, Recurring [Member] Credit-Related Arrangements Concentration Risk, Credit Risk, Policy [Policy Text Block] Cover [Abstract] Cover [Abstract] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Maximum Maximum [Member] Transfer to (out of) other real estate owned Real Estate Owned, Transfer to Real Estate Owned Held-to-maturity Amortized cost Held-to-maturity, amortized cost Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss Other acquired intangible assets, useful life (not exceeding) Finite-Lived Intangible Asset, Useful Life Annual benefit expense Defined Benefit Plan and Defined Contribution Plan, Net Periodic Benefit Cost [Abstract] Defined Benefit Plan and Defined Contribution Plan, Net Periodic Benefit Cost [Abstract] Weighted average rate of compensation increases Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Remaining life expectancy Defined Benefit Plan, Remaining Life Expectancy Defined Benefit Plan, Remaining Life Expectancy Net carrying amount Finite-Lived Intangible Assets, Net Available-for-sale securities with unrealized losses, Total fair value Debt Securities, Available-for-Sale, Unrealized Loss Position Over 10 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Time vesting shares Restricted Stock [Member] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Credit risk concentrations Concentration Risk Disclosure [Text Block] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Financing Receivable, Credit Quality Indicator [Table] Financing Receivable, Credit Quality Indicator [Table] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Cash and cash equivalents, securities purchased under agreements to resell and short-term investments Interest Income, Deposits with Financial Institutions Months of term extension Financing Receivable, Modified, Weighted Average Term Increase from Modification Net income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Leverage ratio, Actual Banking Regulation, Tier 1 Leverage Capital Ratio, Actual Deferred income taxes assets (liabilities) Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Transition Asset (Obligation), after Tax Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments Operating Segments [Member] Share-based settlements Adjustments to Additional Paid in Capital, Share-Based Settlements Adjustments to Additional Paid in Capital, Share-Based Settlements Other intangible assets, net Other Intangible Assets, Net Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Total interest expense Interest expense Interest Expense, Operating Series B Notes Due 2020 Series B Notes Due 2020 [Member] Series B Notes Due 2020 [Member] Offsetting Liabilities [Table] Offsetting Liabilities [Table] Income from operations Income (Loss) from Continuing Operations before Income Taxes, Domestic Software and Software Development Costs Software and Software Development Costs [Member] Document Fiscal Period Focus Document Fiscal Period Focus Weighted average rate of compensation increases Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Derivative Liability, Statement of Financial Position [Extensible Enumeration] Derivative Liability Statement Of Financial Position Extensible Enumeration Not Disclosed Flag Derivative Liability Statement Of Financial Position Extensible Enumeration Not Disclosed Flag Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Return of capital from a subsidiary Proceeds from Divestiture of Businesses and Interests in Affiliates Available-for-sale, amortized cost Amortized cost Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss Award Type [Axis] Award Type [Axis] Unrealized net gains (losses) on translation of net investment in foreign operations Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Hedging Relationship [Domain] Hedging Relationship [Domain] Bank of N.T. Butterfield & Son Ltd Parent Company [Member] Share-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Trading Symbol Trading Symbol 2029 Lessee, Operating Lease, Liability, to be Paid, Year Four Non-interest bearing Cash and Due from Banks [Abstract] Business Combinations Business Combination [Policy Text Block] Pension asset Deferred Tax Liabilities, Pension Asset Deferred Tax Liabilities, Pension Asset Change in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Long-term debt Interest Expense, Long-Term Debt Short-term investments other than restricted cash: proceeds from maturities and sales Short-term investments other than restricted cash: proceeds from maturities and sales Proceeds from Sale, Maturity and Collection of Short-Term Investments Entity Address, City or Town Entity Address, City or Town Investment [Line Items] Marketable Securities [Line Items] Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Net effect of exchange rates on cash, cash equivalents and restricted cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Deferred income tax asset after valuation allowance Deferred Tax Assets, Net of Valuation Allowance Foreign exchange translation adjustment Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Allowance for Credit Losses Credit Loss, Financial Instrument [Policy Text Block] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Guernsey Guernsey Segment [Member] Guernsey Segment [Member] Number of custodians Commitments to Extend Credit, Number of Custodians Commitments to Extend Credit, Number of Custodians Entity Emerging Growth Company Entity Emerging Growth Company Purchase of intangible assets Payments to Acquire Intangible Assets Positions not offset in the consolidated balance sheets, cash collateral received/paid Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Held-to-maturity securities with unrealized losses, Less than 12 months, Gross unrealized losses Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Options outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Condensed financial statements of the parent company only Condensed Financial Information of Parent Company Only Disclosure [Text Block] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Total net gains (losses) recognized in net income Derivative, Gain (Loss) on Derivative, Net 2028 Other Commitment, to be Paid, Year Three 2026 Defined Benefit Plan, Expected Future Benefit Payment, Year One Common shares, outstanding (in shares) Common Stock, Shares, Outstanding Change in deferred taxes Other Comprehensive Income (Loss), Defined Benefit Plan, Transition Asset (Obligation), Reclassification Adjustment from AOCI, after Tax Actuarial assumptions used to determine benefit obligations at end of year Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Schedule of marketable securities Marketable Securities [Table Text Block] Gross unrealized losses Debt Securities, Held-to-Maturity, Accumulated Unrecognized Loss Non-interest expense Noninterest Expense [Abstract] Cash and demand deposits with banks - Non-interest bearing Cash and demand deposits with banks Cash and Due from Banks Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Prepaid benefit cost included in accrued interest and other assets Assets for Plan Benefits, Defined Benefit Plan Cash and cash equivalents Due from Banks Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Gross Guarantor Obligations, Current Carrying Value Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Change in projected benefit obligation Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Weighted average interest rate, demand deposits Weighted Average Interest Rate, Demand Deposits Weighted Average Interest Rate, Demand Deposits Interest rate reduction Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification Changes in Outstanding ELTIP and EDIP Awards Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Pledged Status [Domain] Pledged Status [Domain] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Investments (none of the investment securities are intrinsically tax-exempt) Interest and Dividend Income, Securities, Operating Income tax benefit (expense) Income tax benefit (expense) Total tax (benefit) expense Income Tax Expense (Benefit) Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Accrued interest and other assets Other assets, including accrued interest, premises, equipment and computer software, equity method investments, receivables from subsidiaries and other real estate owned Other Assets Thereafter Time Deposit Maturities, after Year Five Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Hedging Relationship [Axis] Hedging Relationship [Axis] Risk Weighted Assets Banking Regulation, Risk-Weighted Assets, Actual Cost Property, Plant and Equipment, Gross Interest bearing Cash and Due from Banks, Interest-bearing [Abstract] Cash and Due from Banks, Interest-bearing [Abstract] Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Debt securities, available-for-sale, securities in unrealized loss positions, percentage of portfolio fair value Debt Securities, Available-for-sale, Securities In Unrealized Loss Positions, Percentage Of Portfolio Fair Value Debt Securities, Available-for-sale, Securities In Unrealized Loss Positions, Percentage Of Portfolio Fair Value Other Income and Expenses [Abstract] Other Income and Expenses [Abstract] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Custody and other administration services Custody and other administration services Custody and Other Administration Services Revenue Custody and Other Administration Services Revenue Term deposits, by year of maturity Deposits, by Component, Alternative [Abstract] Other Effective Income Tax Rate Reconciliation, Other Adjustments, Amount 2031 & thereafter Other Commitment, to be Paid, after Year Five Deferred income tax liability Deferred Tax Liabilities, Gross [Abstract] Outstanding at beginning of year (in shares) Outstanding at end of year (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Dividends from subsidiaries Dividend Income, Related Parties Dividend Income, Related Parties Tax loss carried forward Deferred Tax Assets, Operating Loss Carryforwards, Foreign Cash provided by (used in) operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Amounts recognized in the consolidated balance sheets consist of: Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract] Average number of outstanding awards of unvested shares (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested, Number of Shares Cayman Cayman Cayman Segment [Member] Cayman Segment [Member] Available-for-sale investments: proceeds from sale Proceeds from Sale of Debt Securities, Available-for-Sale Available-for-sale investments Carrying amount Available-for-sale, fair value Debt Securities, Available-for-Sale, Excluding Accrued Interest Proceeds from sale of other real estate owned Proceeds from Sale of Other Real Estate Preference shares, par value (in dollars per share or pounds per share) Preferred Stock, Par or Stated Value Per Share Amortization Amortization [Abstract] Useful life Property, Plant and Equipment, Useful Life Subsequent Event Subsequent Event [Member] Net interest income before provision for credit losses Net interest income Interest Income (Expense), Operating Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Other expenses Other Noninterest Expense, Marking Expense and Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Other Noninterest Expense, Marking Expense and Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component PEO Total Compensation Amount PEO Total Compensation Amount Tier 1 capital Banking Regulation, Tier 1 Risk-Based Capital, Actual Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Total depreciation charged to operating expenses Depreciation Gross negative fair value Gross fair value recognized Derivative Liability, Subject to Master Netting Arrangement, before Offset Equity Components [Axis] Equity Components [Axis] Loans originated 3 years past Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Sublease income Sublease Income Standby Letters of Credit Standby Letters of Credit [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] 2026 Other Commitment, to be Paid, Year One Non-interest income Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions and Other [Abstract] Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions and Other [Abstract] Number of reportable segments Number of Reportable Segments Weighted average annual medical cost increase rate Defined Benefit Plan, Ultimate Health Care Cost Trend Rate, Net Periodic Benefit Cost Defined Benefit Plan, Ultimate Health Care Cost Trend Rate, Net Periodic Benefit Cost Entity Address, Country Entity Address, Country Schedule of contractual obligation, fiscal year maturity Contractual Obligation, Fiscal Year Maturity [Table Text Block] Substandard Substandard [Member] Total interest income Interest income Interest and Dividend Income, Operating Special mention Special Mention [Member] Financial Asset, Aging [Domain] Financial Asset, Aging [Domain] 2029 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Loans, net of allowance for credit losses Loans Receivable, Fair Value Disclosure Other Financing Receivable, Excluding Accrued Interest, Allowance For Credit Losses, Other Adjustments Financing Receivable, Excluding Accrued Interest, Allowance For Credit Losses, Other Adjustments Foreign Foreign Income Tax Expense (Benefit), Continuing Operations [Abstract] Commercial and industrial Commercial and Industrial Sector [Member] Individual: Individual [Axis] Defined contribution expense Defined Contribution Plan, Cost Income Tax Jurisdiction [Domain] Income Tax Jurisdiction [Domain] Cash dividends paid on common shares Payments of Ordinary Dividends, Common Stock Document Annual Report Document Annual Report Time Deposits [Table] Deposit Liability [Table] Other Defined Benefit Plan, Cash and Cash Equivalents [Member] No specific or single maturity Debt Securities, Available-for-Sale, Maturity, without Single Maturity Date, Amortized Cost Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Repayment of long-term debt Repayments of Long-Term Debt Entity Interactive Data Current Entity Interactive Data Current Common Equity Tier 1, Actual Tier One Common Equity Risk Based Capital to Risk Weighted Assets Tier One Common Equity Risk Based Capital to Risk Weighted Assets Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Available-for-sale Interest Income, Debt Securities, Available-for-Sale, Operating Condensed Income Statement [Table] Condensed Income Statement [Table] Financing Receivable, Troubled Debt Restructuring [Line Items] Financing Receivable, Modified [Line Items] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Net gains (losses) on other real estate owned Net (gains) losses on other real estate owned Gains (Losses) on Sales of Other Real Estate Interest income Interest and Dividend Income, Operating [Abstract] Held-to-maturity securities Held-to-Maturity Securities [Member] Total non-interest expense Total non-interest expense Noninterest Expense Securities purchased under agreements to resell Federal Funds Sold and Securities Borrowed or Purchased under Agreements to Resell, Fair Value Disclosure 2029 Other Commitment, to be Paid, Year Four Total investment in securities Marketable Securities Payments delay in # of months Payment Deferral [Member] Deposits Interest Expense, Deposits Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Axis] Within 1 year Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Within 1 year Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Within 1 year Securities purchased under agreements to resell having original maturities of more than 3 months: proceeds from maturities Proceeds from Securities Purchased under Agreements to Resell 2027 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Schedule of unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost [Table Text Block] Customer [Domain] Customer [Domain] Entity Central Index Key Entity Central Index Key PEO Name PEO Name Non-interest bearing demand deposits Noninterest-Bearing Domestic Deposit, Demand Total net revenue Revenues Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] 2027 Purchase Obligation, to be Paid, Year Two Currency swaps Currency Swap [Member] Schedule of financing receivable credit quality indicators Financing Receivable Credit Quality Indicators [Table Text Block] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Other comprehensive income (loss), net of taxes Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Defined Benefit Plan [Table] Defined Benefit Plan [Table] Non-interest bearing Non-interest bearing Noninterest-Bearing Deposit Liabilities Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Total Tier 1, Regulatory minimum Banking Regulation, Tier 1 Risk-Based Capital Ratio, Capital Adequacy, Minimum Class of Stock [Domain] Class of Stock [Domain] Unrecognized cost Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid Subsequent Event Type [Axis] Subsequent Event Type [Axis] Income tax benefit (expense) Foreign Income Tax Expense (Benefit), Continuing Operations Letters of Guarantee Guarantee of Indebtedness of Others [Member] Weighted average actual and target asset allocations of the pension plans by asset category Defined Benefit Plan, Plan Assets, Allocations [Abstract] Nonrelated Party Nonrelated Party [Member] Post- retirement medical benefit plan Post-retirement healthcare plan Postretirement Health Coverage [Member] Estimated aggregate amortization expense, year three Finite-Lived Intangible Asset, Expected Amortization, Year Three Net income - Domestic Income (Loss) from Continuing Operations, Net of Tax, Domestic Income (Loss) from Continuing Operations, Net of Tax, Domestic Total non- performing loans Loans Financing Receivable, before Allowance for Credit Loss Time vesting and performance vesting shares Time Vesting Shares and Performance Shares [Member] Time Vesting Shares and Performance Shares [Member] Deferred income tax asset Deferred Tax Assets, Net [Abstract] Off-balance sheet Off-balance Sheet [Member] Off-balance Sheet [Member] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Entity Address, Address Line One Entity Address, Address Line One Leverage Ratio Exposure Measure Leverage Ratio Exposure Measure Leverage Ratio Exposure Measure Repayments of debt Repayments of Subordinated Debt Guarantor obligations, term period Guarantor Obligations, Term Period Guarantor Obligations, Term Period Accumulated other comprehensive income (loss) Total AOCIL AOCI Attributable to Parent [Member] Investment Type [Domain] Investments [Domain] Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Balance of unamortized fair value hedge included in loans as at year end Fair Value Hedge Liabilities Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Derivative instruments and risk management Derivative Instruments and Hedging Activities Disclosure [Text Block] Amortization of prior service (credit) loss Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Industry Sector [Axis] Industry Sector [Axis] Collateral Guarantee Obligations, Collateral Amount Guarantee Obligations, Collateral Amount Fair Value as of Grant Date Award Grant Date Fair Value Tax loss carried forward Operating Loss Carryforwards Loans originated 4 years past Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year Salaries and other employee benefits Labor and Related Expense Net dilution impact related to awards of unvested common shares (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Leverage ratio, Regulatory minimum Banking Regulation, Tier 1 Leverage Capital Ratio, Capital Adequacy, Minimum Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Total unrecognized expense Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Forfeitures and cancellations (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Entity Listings [Line Items] Entity Listings [Line Items] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Available-for-sale securities with unrealized losses, Less than 12 months, Fair value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Total Tier 1, Actual Banking Regulation, Tier 1 Risk-Based Capital Ratio, Actual Deposits Deposit Liabilities Disclosures [Text Block] Remaining life expectancy, active members Defined Benefit Plan, Remaining Life Expectancy, Active Members Defined Benefit Plan, Remaining Life Expectancy, Active Members Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Financial Instrument Performance Status [Axis] Financial Instrument Performance Status [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Held-to-maturity securities with unrealized losses, 12 months or more, Gross unrealized losses Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Schedule of non-accrual status for non-performing loans Financing Receivable, Nonaccrual [Table Text Block] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] 2027 Lessee, Operating Lease, Liability, to be Paid, Year Two Condensed Financial Information Disclosure [Abstract] Condensed Financial Information Disclosure [Abstract] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Germany GERMANY Held-to-maturity, securities in unrealized loss positions, percentage of portfolio fair value Held-to-maturity, Securities In Unrealized Loss Positions, Percentage Of Portfolio Fair Value Held-to-maturity, Securities In Unrealized Loss Positions, Percentage Of Portfolio Fair 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