Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Nonrecurring Fair Value, Measurements, Nonrecurring [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 1 inputs Fair Value, Inputs, Level 1 [Member] Level 2 inputs Fair Value, Inputs, Level 2 [Member] Level 3 inputs Fair Value, Inputs, Level 3 [Member] Financial Instrument [Axis] Financial Instrument [Axis] Types of Financial Instruments [Domain] Financial Instruments [Domain] Commercial & industrial Commercial And Industrial [Member] A loan, whether secured or unsecured, to a company for purposes such as seasonal working capital needs, inventory financing, equipment purchases and acquisitions. CRE Commercial Real Estate [Member] Multi-family Real Estate Commercial Mortgage CBL [Member] Real estate commercial mortgage CBL. Residential mortgage Residential Mortgage [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] Portfolio loans, impaired, net Loans Receivable, Fair Value Disclosure Investments, Debt and Equity Securities [Abstract] Number of securities which were in continuous unrealized loss position for less than 12 months Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Number Of Securities Available for sale securities continuous unrealized loss position less than twelve months number of securities. Number of securities which were in continuous unrealized loss position for 12 months or more Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Number Of Securities Available for sale securities continuous unrealized loss position twelve months or longer number of securities. Number of held to maturity securities which were in continuous unrealized loss position for less than 12 months Held To Maturity Securities Continuous Loss Position Less Than Twelve Months Number Of Securities Held To Maturity Securities Continuous Loss Position Less Than Twelve Months Number Of Securities Number of held to maturity securities which were in continuous unrealized loss position for 12 months or more Held To Maturity Securities Continuous Loss Position More Than Twelve Months Number Of Securities Held To Maturity Securities Continuous Loss Position More Than Twelve Months Number Of Securities Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Postemployment Benefits [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category [Domain] PRIAC Pooled Separate Accounts PRIAC Pooled Separate Accounts [Member] PRIAC Pooled Separate Accounts [Member] Sterling Bancorp common stock Sterling Bancorp Common Stock [Member] Sterling Bancorp Common Stock [Member] PRIAC Guaranteed Deposit Account PRIAC Guaranteed Deposit Account [Member] PRIAC Guaranteed Deposit Account [Member] Cash and cash equivalents Defined Benefit Plan, Cash and Cash Equivalents [Member] Fixed income Fixed Income Securities [Member] Large-cap equity Defined Benefit Plan, Equity Securities, Large Cap [Member] International equity Defined Benefit Plan, Equity Securities, Non-US [Member] Small-cap equity Defined Benefit Plan, Equity Securities, Small Cap [Member] Mid-cap equity Defined Benefit Plan, Equity Securities, Mid Cap [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Fair value of plan assets Defined Benefit Plan, Plan Assets, Amount Plan asset allocations Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage Stockholders' Equity Note [Abstract] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Summary of securities available for sale Debt Securities, Available-for-sale [Table Text Block] Summary of securities held-to-maturity Debt Securities, Held-to-maturity [Table Text Block] Summary of amortized cost and fair value of investment securities available for sale by remaining period to contractual maturity Investments Classified by Contractual Maturity Date [Table Text Block] Sale of securities Schedule of Realized Gain (Loss) [Table Text Block] Securities available for sale with unrealized losses, by length of time in continuous unrealized loss position Schedule of Unrealized Loss on Investments [Table Text Block] Securities pledged for borrowings at FHLB and other institutions, and securities pledged for municipal deposits and other purposes Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block] Derivative Instruments and Hedges, Assets [Abstract] Schedule of Credit Derivatives [Table] Schedule of Credit Derivatives [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Third-party interest rate swap Third Party Interest Rate Swap [Member] Third party interest rate swap. Customer interest rate swap Customer Interest Rate Swap [Member] Customer interest rate swap. Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets Other Assets [Member] Other Liabilities Other Liabilities [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] One Month LIBOR One Month Libor [Member] One Month Libor [Member] Credit Derivatives [Line Items] Credit Derivatives [Line Items] Summary of derivatives Summary of Credit Derivatives [Abstract] Derivative assets, notional amount Derivative Asset, Notional Amount Derivative liabilities, notional amount Derivative Liability, Notional Amount Average maturity (in years) Derivative, Average Remaining Maturity Weighted average fixed rate Derivative, Average Fixed Interest Rate Basis spread Derivative, Basis Spread on Variable Rate Derivative assets, fair value Derivative Asset Derivative liabilities, fair value Derivative Liability Receivables [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Multi-family Multifamily [Member] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Commercial Commercial Portfolio Segment [Member] Residential mortgage Residential Portfolio Segment [Member] Consumer Consumer Portfolio Segment [Member] Industry Sector [Axis] Industry Sector [Axis] Industry Sector [Domain] Industry Sector [Domain] Commercial & Industrial (C&I) Commercial and Industrial Sector [Member] Commercial mortgage Real Estate Sector [Member] Credit Loss Status [Axis] Credit Loss Status [Axis] Credit Loss Status [Domain] Credit Loss Status [Domain] Receivables without deteriorated credit quality Receivables Without Deteriorated Credit Quality [Member] Receivables Without Deteriorated Credit Quality [Member] Receivables acquired with deteriorated credit quality Financial Asset Acquired with Credit Deterioration [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] Traditional C&I Asset-based lending Asset-Based Lending [Member] Asset-Based Lending [Member] Payroll finance Payroll Finance [Member] Payroll Finance [Member] Equipment financing Equipment Financing Receivables [Member] A loan related to equipment finance receivable. Real estate loan Real Estate Loan [Member] ADC Acquisition, Development And Construction [Member] Acquisition Development And Construction [Member] Consumer Consumer Loan [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Non accrual loans Financing Receivable, Recorded Investment, Nonaccrual Status Non-accrual loans, unpaid principal balance Financing Receivable, Recorded Investment, Nonaccrual Status, Unpaid Principal Balance Financing Receivable, Recorded Investment, Nonaccrual Status, Unpaid Principal Balance Investments in Affordable Housing Projects [Abstract] Gross investment in LIHTC Amortization Method Qualified Affordable Housing Project Investments, Gross Amortization Method Qualified Affordable Housing Project Investments, Gross Accumulated amortization Amortization Method Qualified Affordable Housing Project Investments, Accumulated Amortization Amortization Method Qualified Affordable Housing Project Investments, Accumulated Amortization Net investment in LIHTC Amortization Method Qualified Affordable Housing Project Investments Unfunded commitments for LIHTC investments Qualified Affordable Housing Project Investments, Commitment Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Amortized costs, one year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Amortized costs, one to five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Amortized costs, five to ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Amortized costs, greater than ten years Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Total other securities Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost Residential MBS Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Amortized cost Debt Securities, Available-for-sale, Amortized Cost Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Fair value, one year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Fair value, one to five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Fair value, five to ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Fair value, greater than ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Fair value, total other securities Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value Fair value, Residential MBS Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Fair value, total securities Debt Securities, Available-for-sale Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract] Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract] Amortized cost, one year or less Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Amortized cost, one to five years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Amortized cost, five to ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Amortized cost, greater than ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Amortized Cost Amortized cost, total other securities Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost Amortized cost, Residential MBS Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Amortized Cost Amortized cost Debt Securities, Held-to-maturity Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract] Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract] Fair value, one year or less Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Fair value, one to five years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Fair value, five to ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Fair value, greater than ten years Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Fair value, total other securities Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value Fair value, Residential MBS Debt Securities, Held-to-maturity, Maturity, without Single Maturity Date, Fair Value Fair value, total securities Debt Securities, Held-to-maturity, Fair Value Schedule of Fair Value, Off-balance Sheet Risks [Table] Schedule of Fair Value, Off-balance Sheet Risks [Table] Letters of credit Letter of Credit [Member] Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] Lending-related instruments Fair Value Disclosure, Off-balance Sheet Risks, Amount, Asset Assets secured by cash as collateral Fair Value Disclosure, Off-balance Sheet Risks, Asset Amount Secured by Cash as Collateral Fair Value Disclosure, Off-balance Sheet Risks, Asset Amount Secured by Cash as Collateral Assets secured by other collateral Fair Value Disclosure, Off-balance Sheet Risks, Asset Amount Secured by Other Collateral Fair Value Disclosure, Off-balance Sheet Risks, Asset Amount Secured by Other Collateral Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred stock Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Common stock, cash dividends paid (USD per share) Common Stock, Dividends, Per Share, Cash Paid Stock issued in merger transaction (in shares) Stock Issued During Period, Shares, Acquisitions Preferred stock, cash dividends paid (USD per share) Preferred Stock, Dividends, Per Share, Cash Paid Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Astoria Financial Corporation Astoria Financial Corporation [Member] Astoria Financial Corporation [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Net interest income Business Acquisition, Pro Forma Interest Income (Expense), Net Business Acquisition, Pro Forma Interest Income (Expense), Net Non-interest income Business Acquisition, Pro Forma Noninterest Income Business Acquisition, Pro Forma Noninterest Income Non-interest expense Business Acquisition, Pro Forma Noninterest Expense Business Acquisition, Pro Forma Noninterest Expense Net income available to common stockholders Business Acquisition, Pro Forma Net Income (Loss) Pro forma earnings per common share from continuing operations: Earnings Per Share, Pro Forma [Abstract] Basic (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Basic Diluted (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Statement of Financial Position [Abstract] ASSETS: Assets [Abstract] Cash and due from banks Cash and Due from Banks Securities: Marketable Securities [Abstract] Available for sale, at fair value Held to maturity, at amortized cost (fair value of $2,740,522 and $2,863,909 at December 31, 2018 and December 31, 2017, respectively) Total securities Marketable Securities Loans Receivable, Net [Abstract] Loans Receivable, Net [Abstract] Loans held for sale Loans Receivable Held-for-sale, Net, Not Part of Disposal Group Portfolio loans Loans and Leases Receivable, Gross Allowance for loan losses Loans and Leases Receivable, Allowance Portfolio loans, net Loans and Leases Receivable, Net Amount Federal Home Loan Bank (“FHLB”) and Federal Reserve Bank stock, at cost Federal Home Loan Bank Stock Accrued interest receivable Interest Receivable Premises and equipment, net Property, Plant and Equipment, Net Goodwill Goodwill Core deposit and other intangible assets Intangible Assets, Net (Excluding Goodwill) Bank owned life insurance Bank Owned Life Insurance Other real estate owned Other Real Estate, Foreclosed Assets, and Repossessed Assets Other assets Other Assets Total assets Assets LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] LIABILITIES: Liabilities [Abstract] Deposits Deposits FHLB borrowings Long-term Federal Home Loan Bank Advances Other borrowings (repurchase agreements) Securities Sold under Agreements to Repurchase Senior notes Senior Notes Subordinated notes Subordinated Debt Mortgage escrow funds Advance Payments by Borrowers for Taxes and Insurance Other liabilities Other Liabilities Total liabilities Liabilities Commitments and Contingent liabilities (See Note 18.) Commitments and Contingencies STOCKHOLDERS’ EQUITY: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock (par value $0.01 per share; 10,000,000 shares authorized; 135,000 shares issued and outstanding at December 31, 2018 and December 31, 2017) Preferred Stock, Value, Issued Common stock (par value $0.01 per share; 310,000,000 shares authorized at December 31, 2018 and December 31, 2017; 229,872,925 shares issued at December 31, 2018 and December 31, 2017; 216,227,852 and 224,782,694 shares outstanding at December 31, 2018 and December 31, 2017, respectively) Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Treasury stock, at cost (13,645,073 shares at December 31, 2018 and 5,090,231 shares at December 31, 2017) Treasury Stock, Value Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss, net of tax benefit of $(25,429) at December 31, 2018 and $(17,083) at December 31, 2017 Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders’ equity Liabilities and Equity Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer lists Customer Lists [Member] NSBC NewStar Business Credit LLC [Member] NewStar Business Credit LLC [Member] Percentage of outstanding common stock acquired Business Acquisition, Percentage of Voting Interests Acquired Loans receivable acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets Premium paid for loans receivable acquired as a percent of gross loans acquired Business Combination, Premium Paid For Loans Receivable, Percent Of Gross Loans Business Combination, Premium Paid For Loans Receivable, Percent Of Gross Loans Premium paid for loans receivable acquired Business Combination, Premium Paid For Loans Receivable, Amount Business Combination, Premium Paid For Loans Receivable, Amount Total liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Restructuring charges Restructuring Charges Estimated useful life Finite-Lived Intangible Asset, Useful Life Goodwill Equity [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Net unrealized holding gain (loss) on AFS securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Net unrealized holding gain (loss) on securities transferred to held to maturity Net Unrealized Holding Gain (Loss) On Securities Transferred To Held-to-maturity [Member] Net Unrealized Holding Gain (Loss) On Securities Transferred To Held-to-maturity [Member] Net unrealized holding gain (loss) on retirement plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated other comprehensive (loss) income AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] 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] Beginning balance Reclassification of the stranded income tax effects from the enactment of the Tax Cuts and Jobs Act of 2017 from accumulated other comprehensive loss Tax Cuts And Jobs Act, Reclassification From AOCI To Retained Earnings, Tax Effect Tax Cuts And Jobs Act, Reclassification From AOCI To Retained Earnings, Tax Effect Other comprehensive (loss) before reclassification OCI, before Reclassifications, Net of Tax, Attributable to Parent Amounts reclassified from AOCI 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 Ending balance Summary of changes in the projected benefit obligation and fair value of plan assets Schedule of Net Funded Status [Table Text Block] Schedule of pre-tax components of accumulated other comprehensive loss Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Schedule of assumptions used for plan Schedule of Assumptions Used [Table Text Block] Components of the net periodic pension expense (benefit) Schedule of Net Benefit Costs [Table Text Block] Schedule of Health Care Cost Trend Rates Schedule of Health Care Cost Trend Rates [Table Text Block] Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block] Schedule of expected benefit payments Schedule of Expected Benefit Payments [Table Text Block] Schedule of Allocation of Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Schedule of Level 3 Plan Assets Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block] Debt Securities, Held-to-maturity [Table] Debt Securities, Held-to-maturity [Table] Financial Instruments [Domain] Agency-backed Agency Securities [Member] CMO/Other MBS Collateralized Mortgage Obligations [Member] Total residential MBS Residential Mortgage Backed Securities [Member] Federal agencies US Government Agencies Debt Securities [Member] Corporate bonds Corporate Debt Securities [Member] State and municipal US States and Political Subdivisions Debt Securities [Member] Other Other Investment Securities [Member] Other investment securities. Total other securities Debt Securities, Excluding Residential Mortgage Backed Securities [Member] Debt Securities, Excluding Residential Mortgage Backed Securities [Member] Schedule of Held-to-maturity Securities [Line Items] Schedule of Held-to-maturity Securities [Line Items] Fair value, less than 12 months Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value Unrealized losses, less than 12 months Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Fair value, 12 months or longer Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value Unrealized losses, 12 months or longer Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Fair value, total Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value Unrealized losses, total Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Premises and equipment, useful life Property, Plant and Equipment, Useful Life Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of Financing Receivables Past Due [Table] Schedule of Financing Receivables Past Due [Table] Receivable Type [Axis] Receivable Type [Axis] Receivable [Domain] Receivable [Domain] Acquired loans Acquired Loan [Member] Acquired Loan [Member] Originated loans Originated Loan [Member] Originated Loan [Member] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Financing Receivables, Period Past Due [Domain] 30-59 days past due Financing Receivables, 30 to 59 Days Past Due [Member] 60-89 days past due Financing Receivables, 60 to 89 Days Past Due [Member] 90 days past due Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Warehouse lending Warehouse Lending [Member] Warehouse lending [Member] Factored receivables Factored Receivables [Member] A loan related to factored receivables. Public sector finance Public Sector Finance [Member] Public Sector Finance [Member] Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Nonperforming loans Nonperforming Financial Instruments [Member] Financing Receivable, Recorded Investment, Past Due [Line Items] Financing Receivable, Recorded Investment, Past Due [Line Items] Non-Performing loans: Non Performing Loans [Abstract] Non performing loans. Current loans Financing Receivable, Recorded Investment, Current Past due loans Financing Receivable, Recorded Investment, Past Due Total portfolio loans TDRs, Current Trouble Debt restructuring current loans Trouble Debt restructuring current loans TDRs, Non-accrual Non Accrual Loans Under Troubled debt restructurings Non accrual loans. Troubled debt restructurings Financing Receivable, Modifications, Recorded Investment Non-performing loans: Non Performing Assets [Abstract] Non performing assets: Loans 90 days past due and still accruing Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing Total non-performing loans Non Performing Loans Total Total non performing loans. Other Income and Expenses [Abstract] Noon-Interest Income and Other Non-Interest Expense Other non-interest expense [Text Block] Other non-interest expense [Text Block] Loans transfered from held for investment to held for sale Transfer of Portfolio Loans and Leases to Held-for-sale Loan purchase accounting adjustments transferred from held for investment to held for sale Transfer Of Portfolio Loans Purchase Accounting Adjustments To Held-for-sale Transfer Of Portfolio Loans Purchase Accounting Adjustments To Held-for-sale Acquisitions Business Combination Disclosure [Text Block] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension benefits Pension Plan [Member] Other post retirement benefits Other Postretirement Benefits Plan [Member] Net actuarial gain (loss) Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Deferred tax (expense) benefit Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Tax Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Tax Amount included in accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Quarterly Financial Information Disclosure [Abstract] Schedule of Quarterly Financial Information Quarterly Financial Information [Table Text Block] Cash pledged as collateral for swaps Derivative, Collateral, Right to Reclaim Cash Changes in projected benefit obligation: Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Beginning of year balance Defined Benefit Plan, Benefit Obligation Benefit obligation assumed in Astoria Merger Defined Benefit Plan, Benefit Obligation, Business Combination Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Actuarial loss Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid Other Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change End of year balance Changes in fair value of plan assets: Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Beginning of year balance Fair value of pension plan assets at October 2, 2017 Defined Benefit Plan, Plan Assets, Business Combination Actual gain on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Benefits paid Defined Benefit Plan, Plan Assets, Benefits Paid End of year balance Reversion asset / Funded status at end of year Defined Benefit Plan, Funded (Unfunded) Status of Plan Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Advantage Funding Management Co., Inc. Advantage Funding Management Co., Inc. [Member] Advantage Funding Management Co., Inc. [Member] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Beginning of period balance Acquired goodwill Goodwill, Acquired During Period Adjustment to provisional goodwill from Astoria Merger Goodwill, Purchase Accounting Adjustments End of period balance 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] Sterling National Bank Subsidiaries [Member] Sterling Bancorp Parent Company [Member] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Regulatory Capital Requirements [Abstract] Regulatory Capital Requirements [Abstract] Common equity tier 1 to RWA: Tier One Common Equity [Abstract] Tier One Common Equity [Abstract] Tier 1 common equity, actual, capital amount Common Equity Tier One Capital Tier 1 common equity, actual, ratio Common Equity Tier One Capital Ratio Tier 1 common equity required for minimum capital adequacy, phase-in schedule, capital amount Tier One Common Capital Required For Capital Adequacy, Phase-In Schedule Tier One Common Capital Required for Capital Adequacy, Phase-In Schedule Tier 1 common equity required for minimum capital adequacy ratio, phase-in schedule, ratio Tier One Common Capital Required For Capital Adequacy To Risk Weighted Assets, Phase-In Schedule Tier One Common Capital Required For Capital Adequacy To Risk Weighted Assets, Phase-In Schedule Tier 1 common equity required for minimum capital adequacy, fully phased-in, capital amount Tier One Common Capital Required For Capital Adequacy, Fully Phased-In Tier One Common Capital Required For Capital Adequacy, Fully Phased-In Tier 1 common equity required for minimum capital adequacy ratio, phase-in schedule, ratio Tier One Common Capital Required For Capital Adequacy To Risk Weighted Assets, Fully Phased-In Tier One Common Capital Required For Capital Adequacy To Risk Weighted Assets, Fully Phased-In Tier 1 common equity required to be well capitalized, capital Common Equity Tier One Capital Required to be Well-Capitalized Tier 1 common equity required to be well capitalized, ratio Tier One Common Capital Required To Be Well Capitalized To Risk Weighted Assets Tier One Common Capital Required To Be Well Capitalized To Risk Weighted Assets Tier 1 capital to RWA: Tier One Risk Based Capital [Abstract] Tier 1 risk-based capital, actual, capital amount Tier One Risk Based Capital Tier 1 risk-based capital, actual, ratio Tier One Risk Based Capital to Risk Weighted Assets Tier 1 risk-based capital required for minimum capital adequacy, phase-in schedule, capital amount Tier One Risk Based Capital Required For Capital Adequacy, Phase-In Schedule Tier One Risk Based Capital Required For Capital Adequacy, Phase-In Schedule Tier 1 risk-based capital required for minimum capital adequacy ratio, phase-in schedule, ratio Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets, Phase-In Schedule Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets, Phase-In Schedule Tier 1 risk-based capital required for minimum capital adequacy, fully phased-in, capital amount Tier One Risk Based Capital Required For Capital Adequacy, Fully Phased-In Tier One Risk Based Capital Required For Capital Adequacy, Fully Phased-In Tier 1 risk-based capital required for minimum capital adequacy, fully phased-in, ratio Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets, Fully Phased-In Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets, Fully Phased-In Tier 1 risk-based capital required to be well capitalized, capital amount Tier One Risk Based Capital Required to be Well Capitalized Tier 1 risk-based capital required to be well capitalized, ratio Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Total capital to RWA: Capital [Abstract] Total risk-based capital, actual, capital amount Capital Total risk-based capital, actual, ratio Capital to Risk Weighted Assets Total risk-based capital required for minimum capital adequacy, phase-in schedule, capital amount Capital Required For Capital Adequacy, Phase-In Schedule Capital Required For Capital Adequacy, Phase-In Schedule Total risk-based capital required for minimum capital adequacy ratio, phase-in schedule, ratio Capital Required For Capital Adequacy To Risk Weighted Assets, Phase-In Schedule Capital Required For Capital Adequacy To Risk Weighted Assets, Phase-In Schedule Total risk-based capital required for minimum capital adequacy, fully phased-in, capital amount Capital Required For Capital Adequacy, Fully Phased-In Capital Required For Capital Adequacy, Fully Phased-In Total risk-based capital required for minimum capital adequacy ratio, fully phased-in, ratio Capital Required For Capital Adequacy To Risk Weighted Assets, Fully Phased-In Capital Required For Capital Adequacy To Risk Weighted Assets, Fully Phased-In Total risk-based capital required to be well capitalized, capital amount Capital Required to be Well Capitalized Total risk-based capital required to be well capitalized, ratio Capital Required to be Well Capitalized to Risk Weighted Assets Tier 1 leverage ratio: Tier One Leverage Capital [Abstract] Tier 1 leverage ratio, actual, capital amount Tier One Leverage Capital Tier 1 (core) capital, actual, ratio Tier One Leverage Capital to Average Assets Tier 1 (core) capital required for minimum capital adequacy, phase-in schedule, capital amount Tier One Leverage Capital Required For Capital Adequacy, Phase-In Schedule Tier One Leverage Capital Required For Capital Adequacy, Phase-In Schedule Tier 1 (core) capital required for minimum capital adequacy ratio, phase-in schedule, ratio Tier One Leverage Capital Required For Capital Adequacy To Average Assets, Phase-In Schedule Tier One Leverage Capital Required For Capital Adequacy To Average Assets, Phase-In Schedule Tier 1 (core) capital required for minimum capital adequacy, fully phased- in, capital amount Tier One Leverage Capital Required For Capital Adequacy, Fully Phased-In Tier One Leverage Capital Required For Capital Adequacy, Fully Phased-In Tier 1 (core) capital required for minimum capital adequacy ratio, fully phased-in, ratio Tier One Leverage Capital Required For Capital Adequacy To Average Assets, Fully Phased-In Tier One Leverage Capital Required For Capital Adequacy To Average Assets, Fully Phased-In Tier 1 (core) capital required to be well capitalized, capital amount Tier One Leverage Capital Required to be Well Capitalized Tier 1 (core) capital required to be well capitalized, ratio Tier One Leverage Capital Required to be Well Capitalized to Average Assets Financial Instruments Owned and Pledged as Collateral [Table] Financial Instruments Owned and Pledged as Collateral [Table] Collateral [Axis] Collateral [Axis] Collateral [Domain] Collateral [Domain] Collateral Pledged Collateral Pledged [Member] Federal Home Loan Bank Borrowings Federal Home Loan Bank Borrowings [Member] Municipal Deposits Municipal Deposits [Member] Municipal deposits. Financial Instruments Owned and Pledged as Collateral [Line Items] Financial Instruments Owned and Pledged as Collateral [Line Items] Available-for-sale securities pledged as collateral Debt Securities, Available-for-sale, Restricted Held-to-maturity securities pledged as collateral Debt Securities, Held-to-maturity, Restricted Total securities pledged Restricted Investments Summary of derivatives Schedule of Derivative Instruments [Table Text Block] Available for sale Debt Securities, Available-for-sale [Abstract] Proceeds from sales of securities available for sale Proceeds from Sale of Debt Securities, Available-for-sale Gross realized gains Debt Securities, Available-for-sale, Realized Gain Gross realized losses Debt Securities, Available-for-sale, Realized Loss Income tax (benefit) expense on realized net (losses) gains Tax Expense (Benefit) Of Securities Gains Tax expense (benefit) of securities gains Held to maturity Debt Securities, Held-to-maturity [Abstract] Proceeds from sales of securities held to maturity Proceeds from Sale of Held-to-maturity Securities Gross realized loss Debt Securities, Held-to-maturity, Sold, Realized Gain (Loss) Income tax (benefit) on realized loss Tax expense held to maturity security gains Tax expense held to maturity security gains Commitments and Contingencies Disclosure [Abstract] Schedule of future minimum lease payments due Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Core deposits Core Deposits [Member] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Number of reporting units Number of Reporting Units Acquired intangible assets, weighted average useful life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Deposits [Abstract] Deposits Deposit Liabilities Disclosures [Text Block] Debt Instruments [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Subordinated Notes Subordinated Debt [Member] Line of Credit Line of Credit [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Senior Note, 5.50% Senior Note, 5.50% [Member] Senior Note, 5.50% [Member] Senior Notes, 3.50% Senior Notes, 3.50% [Member] Senior Notes, 3.50% [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Fair value adjustments Scenario, Adjustment [Member] Three-month LIBOR Three-Month London Interbank Offered Rate [Member] Three-Month London Interbank Offered Rate [Member] London Interbank Offered Rate (LIBOR) London Interbank Offered Rate (LIBOR) [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Bank pledged mortgages Pledged Assets Separately Reported, Loans Pledged as Collateral, at Fair Value Increased borrowing capacity by pledging securities Market Value Of Mortgage Not Required To Be Pledged Market value of mortgage not required to be pledged. Repurchase agreements maturity Repurchase Agreements, Maturity Period Repurchase Agreements, Maturity Period Long-term debt Long-term Debt Fixed interest rate Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate Private placement discount rate Private placement discount rate Private placement discount rate Debt assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Interest rate Debt Instrument, Interest Rate, Stated Percentage Percentage of acquisition date fair value recorded Fair Value, Debt Assumed, Percentage Recorded For Estimated Fair Value Fair Value, Debt Assumed, Percentage Recorded For Estimated Fair Value Debt, fair value adjustment Debt Instrument, Fair Value Disclosure Effective yield, rate Long-term Debt, Weighted Average Interest Rate, at Point in Time Amount of debt redeemed Extinguishment of Debt, Amount Gain on extinguishment of debt Gain (Loss) on Extinguishment of Debt Principal amount Debt Instrument, Face Amount Debt issuance costs Debt Issuance Costs, Gross Issue premium Debt Instrument, Issue Premium, Percentage Debt Instrument, Issue Premium, Percentage Unamortized discount Debt Instrument, Unamortized Discount Effective yield Debt Instrument, Interest Rate, Effective Percentage Basis spread rate Debt Instrument, Basis Spread on Variable Rate Revolving line of credit amount Line of Credit Facility, Maximum Borrowing Capacity Revolving line of credit balance Long-term Line of Credit Property, Plant and Equipment [Abstract] Premises and Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Portfolio Loans Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Series A Preferred Stock Series A Preferred Stock [Member] Series C Preferred Stock Series C Preferred Stock [Member] Class of Stock [Line Items] Class of Stock [Line Items] Allowance for subordinated notes Tier Two Risk Based Capital Aggregate dividend capacity without prior regulatory approval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock (in shares) Preferred stock dividend rate Preferred Stock, Dividend Rate, Percentage Preferred stock, par value (USD per share) Preferred Stock, Par or Stated Value Per Share Preferred stock liquidation preference (USD per share) Preferred Stock, Liquidation Preference Per Share Depositary shares issued (in shares) Depositary Shares Issued Depositary Shares Issued Shares available for repurchase program (shares) Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased Shares authorized to be repurchased (in shares) Stock Repurchase Program, Number of Shares Authorized to be Repurchased Purchase of treasury stock (in shares) Treasury Stock, Shares, Acquired Purchase of treasury stock, wieghted average price (USD per share) Treasury Stock Acquired, Average Cost Per Share Payments for repurchase of common stock Payments for Repurchase of Common Stock Shares repurchased under repurchase program (shares) Stock Repurchased During Period, Shares Liquidation account Liquidation Account Liquidation Account Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] GE Capital GE Capital [Member] GE Capital [Member] Portfolio loan acquired, unpaid principal balance Loans And Leases Receivable, Unpaid Principal Balance Loans And Leases Receivable, Unpaid Principal Balance Portfolio loans purchased Payments to Acquire Loans Receivable Discount rate on acquired portfolio loan Loans and Leases Receivable, Purchase Discount Rate Loans And Leases Receivable, Purchase Discount Rate Discount amount on acquired loan receivable Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums Schedule of Financing Receivable, Allowance for Credit Losses [Table] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Consumer loans, including home equity Financing Receivable, Allowance for Credit Losses [Line Items] Financing Receivable, Allowance for Credit Losses [Line Items] Maximum loan balance for credit risk to be evaluated on a homogeneous basis Minimum Loan Balance for Credit Risk to be Evaluated on a Homogeneous Basis Minimum Loan Balance for Credit Risk to be Evaluated on a Homogeneous Basis Duration period past due for charge off Allowance for Credit Losses, Duration Past Due Until Chargeoff Allowance for Credit Losses, Duration Past Due Until Chargeoff Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Third-Party Technique Third-Party Technique [Member] Third-Party Technique [Member] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Mainly value of taxi medallions Measurement Input, Value Of Taxi Medallions [Member] Measurement Input, Value Of Taxi Medallions [Member] Adjustments for comparable properties Measurement Input, Comparability Adjustment [Member] Adjustments by management to reflect current conditions/selling costs Measurement Input, Cost to Sell [Member] Discount rates Measurement Input, Discount Rate [Member] Prepayment speeds Measurement Input, Prepayment Rate [Member] Multi-family Multi-family financing [Member] Multi-family financing [Member] Mortgage servicing rights Mortgage Servicing Rights [Member] Mortgage Servicing Rights [Member] Loan Status [Axis] Loan Status [Axis] Loan Status [Axis] Loan Status [Domain] Loan Status [Domain] Loan Status [Domain] Impaired Impaired [Member] Impaired [Member] Taken in Foreclosure Taken in Foreclosure [Member] Taken in Foreclosure [Member] Weighted Average Weighted Average [Member] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Assets taken in foreclosure, defaulted loans and facilities held for sale Mortgage servicing rights Servicing Asset at Fair Value, Amount Impaired loans, measurement input Impaired Loans, Measurement Input Impaired Loans, Measurement Input Assets taken in foreclosure, measurement input Other Real Estate, Foreclosed Assets, And Repossessed Asset, Measurement Input Other Real Estate, Foreclosed Assets, And Repossessed Asset, Measurement Input Mortgage servicing rights, measurement input Servicing Asset, Measurement Input Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Financing Receivable, Modifications [Line Items] Financing Receivable, Modifications [Line Items] Current loans Non-accrual Borrowings, Senior Notes and Subordinated Notes Debt Disclosure [Text Block] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Schedule of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Future amortization expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Off-Balance-Sheet Financial Instruments Concentration Risk Disclosure [Text Block] Interest and dividend income Interest and Dividend Income, Operating Interest expense Interest Expense Net interest income Interest Income (Expense), Net Provisions for loan losses Provision for Loan and Lease Losses Non-interest income Noninterest Income 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 Net Income (Loss) Attributable to Parent Preferred stock dividends Preferred Stock Dividends and Other Adjustments Net income available to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Basic (USD per share) Earnings Per Share, Basic Diluted (USD per share) Earnings Per Share, Diluted Deferred tax adjustment related to reduction in federal income tax rate Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Merger-related expense Business Combination, Acquisition Related Costs Other restructuring charges Asset Impairment, Severance, And Retention Charges Asset Impairment, Severance, And Retention Charges CRE Commercial Real Estate Portfolio Segment [Member] Multi-family Summary of activity in allowance for loan losses and recorded investments in loans by portfolio segment based on impairment method Allowance for Loan and Lease Losses [Roll Forward] Beginning balance Charge-offs Financing Receivable, Allowance for Credit Losses, Write-downs Recoveries Financing Receivable, Allowance for Credit Losses, Recovery Net charge-offs Allowance For Doubtful Accounts Receivable, Charge-Offs (Recoveries), Net Allowance For Doubtful Accounts Receivable, Charge-Offs (Recoveries), Net Provision Provision for Loan, Lease, and Other Losses Ending balance Annualized net charge-offs to average loans outstanding Net Charge Offs To Average Gross Loans Annualized Net charge offs to average gross loans annualized. Loan origination commitments Loan Origination Commitments [Member] Unused lines of credit Unused lines of Credit [Member] Estimated fair value on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Impaired loans measured at estimated fair value on nonrecurring basis Fair Value Measurements, Nonrecurring [Table Text Block] Quantitative information of Level 3 assets Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Carrying amounts and estimated fair value of financial assets and liabilities Fair Value, by Balance Sheet Grouping [Table Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Stock options Employee Stock Option [Member] Non-vested stock awards/performance units Non-vested Stock Awards and Performance Units [Member] Non-vested Stock Awards and Performance Units [Member] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Stock-based compensation expense Allocated Share-based Compensation Expense Stock-based compensation expense, income tax benefit Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Corporate bonds State and municipal Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Gross unrealized gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Gross unrealized losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Held to maturity Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract] Gross unrealized gains Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain Gross unrealized losses Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss Fair value Number Financing Receivable, Modifications, Number of Contracts Recorded investment, Pre-modification Financing Receivable, Modifications, Pre-Modification Recorded Investment Recorded investment, Post-modification Financing Receivable, Modifications, Post-Modification Recorded Investment Fair value, less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Unrealized losses, less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Fair value, 12 months or longer Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Unrealized losses, 12 months or longer Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Fair value, total Debt Securities, Available-for-sale, Unrealized Loss Position Unrealized losses, total Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Less than one year Time Deposit Maturities, Next Twelve Months One to two years Time Deposit Maturities, Year Two Two to three years Time Deposit Maturities, Year Three Three to four years Time Deposit Maturities, Year Four Four to five years Time Deposit Maturities, Year Five Total certificates of deposit Certificates Of Deposit Certificates of deposit. 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 year Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Acquisition Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Additions Accretion Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion Charge-offs Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Accretable Yield, Charge-Offs Of Loan Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Accretable Yield, Charge-Offs Of Loan Disposals Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Disposals of Loans Reclassifications to non-accretable difference Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Transfers to Loans Held-for-sale Reclassification from non-accretable difference Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference Balance at end of year Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years 2024 and thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total future minimum payments Operating Leases, Future Minimum Payments Due Rent expense Operating Leases, Rent Expense Schedule of Other Non-interest Expense Other non- interest expense [Table Text Block] Other non- interest expense [Table Text Block] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Health care cost trend rate assumed for the next year Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Rate to which the cost trend rate is assumed to decline (the “ultimate trend rate”) Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Year that ultimate trend rate is reached Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate On percentage point increase, effect on total service and interest cost components Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components On percentage point increase, effect on the post retirement benefit obligation Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation On percentage point decrease, effect on total service and interest cost components Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components On percentage point decrease, effect on the post retirement benefit obligation Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation Schedule of off-balance-sheet financial instruments Schedule of Fair Value, Off-balance Sheet Risks [Table Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal Group, Held-for-sale, Not Discontinued Operations Disposal Group, Held-for-sale, Not Discontinued Operations [Member] Retirement Plan Name [Axis] Retirement Plan Name [Axis] Retirement Plan Name [Domain] Retirement Plan Name [Domain] Astoria Bank Pension Plan Astoria Bank Pension Plan [Member] Astoria Bank Pension Plan [Member] Pension Plans Excluding Astoria Pension Plans Excluding Astoria [Member] Pension Plans Excluding Astoria [Member] Employee Savings Plan Employee Savings Plan [Member] Employee Savings Plan [Member] Liquidity funds Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Over funded amount included in other assets Employer contributions to fund pension plan Maximum contribution by employee, percent Defined Contribution Plan, Maximum Contribution by Employee, Percent Defined Contribution Plan, Maximum Contribution by Employee, Percent Maximum annual contribution per employee, percent Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Savings plan expense Defined Contribution Plan, Cost Condensed Financial Information Disclosure [Abstract] Schedule of Condensed Financial Statements [Table] Condensed Financial Statements [Table] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Assets: Cash Cash and Cash Equivalents, at Carrying Value Investment in the Bank Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Trade name Indefinite-Lived Trade Names Liabilities: Senior Notes Other liabilities Stockholders’ equity Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Net Asset (Liability) [Abstract] Fair Value, Net Asset (Liability) [Abstract] Investment securities available for sale: Investment Securities Available For Sale [Abstract] Investment securities available for sale. Securities available for sale Swaps Total assets Assets, Fair Value Disclosure Swaps, liabilities Total liabilities Financial and Nonfinancial Liabilities, Fair Value Disclosure Summary of major classification of deposits Schedule Of Major Classification Of Deposits [Table Text Block] Major classification of deposits. Schedule of Maturities of Deposits Schedule of Maturities of Deposits [Table Text Block] Schedule of Maturities of Deposits [Table Text Block] List of Company's Brokered deposits Schedule of List of Brokered Deposits [Table Text Block] Schedule of list of brokered deposits. FHLB advances and overnight Federal Home Loan Bank Advances [Member] Repurchase agreements Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member] Subordinated Notes Schedule of debt Long-term Debt, by Category, Current and Noncurrent [Abstract] By period to maturity: Long-term Debt, Rolling Maturity [Abstract] Less than one year, amount Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months Less than one year, rate Long Term Debt Maturities Weighted Average Interest Rate In Next Rolling Twelve Months Long term debt maturities weighted average interest rate in next rolling twelve months. One to two years, amount Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two One to two years, rate Long Term Debt Maturities Weighted Average Interest Rate In Rolling Year Two Long term debt maturities weighted average interest rate in rolling year two. Two to three years, amount Long-term Debt, Maturities, Repayments of Principal in Rolling Year Three Two to three years, rate Long Term Debt Maturities Weighted Average Interest Rate In Rolling Year Three Long term debt maturities weighted average interest rate in rolling year three. Three to four years, amount Long-term Debt, Maturities, Repayments of Principal in Rolling Year Four Three to four years, rate Long Term Debt Maturities Weighted Average Interest Rate In Rolling Year Four Long term debt maturities weighted average interest rate in rolling year four. Greater than five years, amount Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five Greater than five years, rate Long Term Debt Maturities Weighted Average Interest Rate In Rolling After Year Five Long term debt maturities weighted average interest rate in rolling after year five. Total borrowings, amount Total borrowings, rate Earnings Per Share [Abstract] Computation of basic and diluted earnings per share: Earnings Per Share, Basic and Diluted [Abstract] Net income available to common stockholders Weighted average common shares outstanding for computation of basic EPS (in shares) Weighted Average Number of Shares Outstanding, Basic Common-equivalent shares due to the dilutive effect of stock options (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Weighted average common shares for computation of diluted EPS (in shares) Weighted Average Number of Shares Outstanding, Diluted Basic (loss) earnings per common share (USD per share) Diluted (loss) earnings per common share (USD per share) Weighted average common shares that could be exercised that were anti-dilutive for the period (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Tier One Risk Based Capital [Abstract] Total U.S. GAAP stockholders’ equity Disallowed goodwill and other intangible assets Reconciliation of Stockholders' Equity to Regulatory Capital, Reconciling Items, Intangible Assets (Including Goodwill) Reconciliation of Stockholders' Equity to Regulatory Capital, Reconciling Items, Intangible Assets (Including Goodwill) Net unrealized loss on available for sale securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Net accumulated other comprehensive income components Tier 1 risk-based capital Tier Two Risk Based Capital [Abstract] Tier Two Risk Based Capital [Abstract] Tier 2 capital Allowance for loan losses and off-balance sheet commitments Total risk-based capital Summary of Company's stock option activity Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block] Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block] Schedule of stock-based compensation expense associated with stock options and non-vested stock awards Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of debt Schedule of Debt [Table Text Block] 2019 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Total Finite-Lived Intangible Assets, Net Activity in Investments in Low Income Housing Tax Credits Activity in Affordable Housing Program Obligation [Table Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Non-compete agreements Noncompete Agreements [Member] Trade name Trade Names [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Gross intangible assets Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Net intangible assets Amortization of intangible assets Amortization of Intangible Assets Factored receivables Loans acquired transferred to originated Loans And Leases Receivable, Gross, Reclassified From Acquired To Originated Loans And Leases Receivable, Gross, Reclassified From Acquired To Originated Loans And Leases Receivable, Allowance, Transfered From Acquired To Origniated Loans And Leases Receivable, Allowance, Transfered From Acquired To Origniated Loans And Leases Receivable, Allowance, Transfered From Acquired To Origniated Net deferred loan origination costs Purchase accounting adjustments to loans Business Combination, Provisional Information, Initial Accounting Incomplete, Loans Business Combination, Provisional Information, Initial Accounting Incomplete, Loans Pledged loans recorded investment of PCI non-accrual loans, transferred from acquired to originated Financing Receivable, Recorded Investment, Nonaccrual Status, Transferred From Acquired To Originated Financing Receivable, Recorded Investment, Nonaccrual Status, Transferred From Acquired To Originated Loans formally in process of foreclosure Mortgage Loans in Process of Foreclosure, Amount PCI loans Financing Receivable, Net Cash-basis interest income recognized Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method Impaired loans with related allowance recorded Impaired Financing Receivable, with Related Allowance, Recorded Investment Number of contracts, troubled debt restructurings Recorded investment, pre-modification Recorded investment, post-modification Charge-offs Charge Offs From Troubled Debt Restructurings Charge Offs From Troubled Debt Restructurings Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income 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] Charge of asset write-downs, systems integration, severance and retention Restructuring Costs and Asset Impairment Charges (Gain) loss on extinguishment of borrowings (Gain) loss and write-downs on other real estate owned Gains (Losses) on Sales of Other Real Estate (Gain) loss on sale of premises and equipment Gain (Loss) on Disposition of Property Plant Equipment Depreciation and amortization of premises and equipment Depreciation, Depletion and Amortization Amortization of intangibles Amortization of low income housing tax credits Amortization Method Qualified Affordable Housing Project Investments, Amortization Net gains on loans held for sale Gain (Loss) on Sales of Loans, Net Net losses (gains) on sales of securities Debt and Equity Securities, Gain (Loss) Net (gain) on sale of trust division Gain (Loss) on Disposition of Assets Net (accretion) on loans Accretion (Amortization) of Discounts and Premiums, Loans Accretion (Amortization) of Discounts and Premiums, Loans Net amortization of premiums on securities Accretion (Amortization) of Discounts and Premiums, Investments Amortization of premium on certificates of deposit Accretion (Amortization) Of Discounts And Premiums, Certificates Of Deposit Accretion (Amortization) Of Discounts And Premiums, Certificates Of Deposit Net (amortization of premium) accretion of discount, on borrowings Amortization of Debt Discount (Premium) Restricted stock expense Restricted Stock or Unit Expense Stock option compensation expense Stock or Unit Option Plan Expense Originations of loans held for sale Payments for Origination and Purchases of Loans Held-for-sale Proceeds from sales of loans held for sale Proceeds from Sale of Loans Held-for-sale Increase in cash surrender value of BOLI Life Insurance, Corporate or Bank Owned, Change in Value Deferred income tax expense (benefit) Increase (Decrease) in Deferred Income Taxes Other adjustments (principally net changes in other assets and other liabilities) Other Operating Activities, Cash Flow Statement 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] Purchases of securities: Payments to Acquire Investments [Abstract] Available for sale Payments to Acquire Debt Securities, Available-for-sale Held to maturity Payments to Acquire Held-to-maturity Securities Proceeds from maturities, calls and other principal payments on securities: Proceeds from Sale, Maturity and Collection of Investments [Abstract] Available for sale Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Held to maturity Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Loan originations, net Payments for Loan originations Cash outflows for the origination of new loans during the period. Portfolio loans purchased Proceeds from sale of loans held for investment Proceeds from Sale of Loans Held-for-investment Proceeds from sales of other real estate owned Proceeds from Sale of Other Real Estate Purchase of FHLB and FRB stock, net Payments for (Proceeds from) Federal Home Loan Bank Stock Purchase of low income housing tax credit Payments to Acquire Affordable Housing Tax Credit Payments to Acquire Affordable Housing Tax Credit Redemption of and benefits received on bank owned life insurance Proceeds from Life Insurance Policy Purchases of premises and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from the sale of premises and equipment Proceeds from Sale of Property, Plant, and Equipment Cash (paid for) received from acquisitions Payments for (Proceeds from) Businesses and Interest in Affiliates Net cash (used in) 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 transaction, savings and money market deposits Net Change Interest and Noninterest-bearing Deposits, Domestic Net increase (decrease) in time deposits Increase (Decrease) in Time Deposits Net (decrease) increase in short-term FHLB borrowings Increase (Decrease) in Loans from Federal Home Loan Banks Advances of term FHLB borrowings Proceeds from FHLBank Borrowings, Financing Activities Repayments of term FHLB borrowings Payments of FHLBank Borrowings, Financing Activities Net (decrease) increase in other borrowings Proceeds fr