3.20.4 html 874 682 1 true 184 0 false 17 false false R1.htm 000010001 - Document - Cover Sheet http://www.flagstar.com/role/Cover Cover Cover 1 false false R2.htm 100010002 - Statement - Consolidated Statements of Financial Condition Sheet http://www.flagstar.com/role/ConsolidatedStatementsofFinancialCondition Consolidated Statements of Financial Condition Statements 2 false false R3.htm 100020003 - Statement - Consolidated Statements of Financial Condition (Parenthetical) Sheet http://www.flagstar.com/role/ConsolidatedStatementsofFinancialConditionParenthetical Consolidated Statements of Financial Condition (Parenthetical) Statements 3 false false R4.htm 100030004 - Statement - Consolidated Statements of Operations Sheet http://www.flagstar.com/role/ConsolidatedStatementsofOperations Consolidated Statements of Operations Statements 4 false false R5.htm 100040005 - Statement - Consolidated Statements of Comprehensive Income Sheet http://www.flagstar.com/role/ConsolidatedStatementsofComprehensiveIncome Consolidated Statements of Comprehensive Income Statements 5 false false R6.htm 100050006 - Statement - Consolidated Statements of Stockholders' Equity Sheet http://www.flagstar.com/role/ConsolidatedStatementsofStockholdersEquity Consolidated Statements of Stockholders' Equity Statements 6 false false R7.htm 100060007 - Statement - Consolidated Statements of Cash Flows Sheet http://www.flagstar.com/role/ConsolidatedStatementsofCashFlows Consolidated Statements of Cash Flows Statements 7 false false R8.htm 210011001 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPolicies Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies Notes 8 false false R9.htm 210091002 - Disclosure - Investment Securities Sheet http://www.flagstar.com/role/InvestmentSecurities Investment Securities Notes 9 false false R10.htm 210171003 - Disclosure - Loans Held-for-Sale Sheet http://www.flagstar.com/role/LoansHeldforSale Loans Held-for-Sale Notes 10 false false R11.htm 210191004 - Disclosure - Loans Held-for-Investment Sheet http://www.flagstar.com/role/LoansHeldforInvestment Loans Held-for-Investment Notes 11 false false R12.htm 210291005 - Disclosure - Loans with Government Guarantees Sheet http://www.flagstar.com/role/LoanswithGovernmentGuarantees Loans with Government Guarantees Notes 12 false false R13.htm 210311006 - Disclosure - Repossessed Assets Sheet http://www.flagstar.com/role/RepossessedAssets Repossessed Assets Notes 13 false false R14.htm 210351007 - Disclosure - Variable Interest Entities Sheet http://www.flagstar.com/role/VariableInterestEntities Variable Interest Entities Notes 14 false false R15.htm 210371008 - Disclosure - Federal Home Loan Bank Stock Sheet http://www.flagstar.com/role/FederalHomeLoanBankStock Federal Home Loan Bank Stock Notes 15 false false R16.htm 210391009 - Disclosure - Premises and Equipment Sheet http://www.flagstar.com/role/PremisesandEquipment Premises and Equipment Notes 16 false false R17.htm 210431010 - Disclosure - Mortgage Servicing Rights Sheet http://www.flagstar.com/role/MortgageServicingRights Mortgage Servicing Rights Notes 17 false false R18.htm 210481011 - Disclosure - Derivative Financial Instruments Sheet http://www.flagstar.com/role/DerivativeFinancialInstruments Derivative Financial Instruments Notes 18 false false R19.htm 210541012 - Disclosure - Deposit Accounts Sheet http://www.flagstar.com/role/DepositAccounts Deposit Accounts Notes 19 false false R20.htm 210581013 - Disclosure - Borrowings Sheet http://www.flagstar.com/role/Borrowings Borrowings Notes 20 false false R21.htm 210651014 - Disclosure - Accumulated Other Comprehensive Income Sheet http://www.flagstar.com/role/AccumulatedOtherComprehensiveIncome Accumulated Other Comprehensive Income Notes 21 false false R22.htm 210681015 - Disclosure - Earnings Per Share Sheet http://www.flagstar.com/role/EarningsPerShare Earnings Per Share Notes 22 false false R23.htm 210711016 - Disclosure - Stock-Based Compensation Sheet http://www.flagstar.com/role/StockBasedCompensation Stock-Based Compensation Notes 23 false false R24.htm 210751017 - Disclosure - Income Taxes Sheet http://www.flagstar.com/role/IncomeTaxes Income Taxes Notes 24 false false R25.htm 210811018 - Disclosure - Regulatory Capital Sheet http://www.flagstar.com/role/RegulatoryCapital Regulatory Capital Notes 25 false false R26.htm 210841019 - Disclosure - Legal Proceedings, Contingencies and Commitments Sheet http://www.flagstar.com/role/LegalProceedingsContingenciesandCommitments Legal Proceedings, Contingencies and Commitments Notes 26 false false R27.htm 210881020 - Disclosure - Fair Value Measurements Sheet http://www.flagstar.com/role/FairValueMeasurements Fair Value Measurements Notes 27 false false R28.htm 210991021 - Disclosure - Segment Information Sheet http://www.flagstar.com/role/SegmentInformation Segment Information Notes 28 false false R29.htm 211021022 - Disclosure - Holding Company Only Financial Statements Sheet http://www.flagstar.com/role/HoldingCompanyOnlyFinancialStatements Holding Company Only Financial Statements Notes 29 false false R30.htm 211071023 - Disclosure - Quarterly Financial Data (Unaudited) Sheet http://www.flagstar.com/role/QuarterlyFinancialDataUnaudited Quarterly Financial Data (Unaudited) Notes 30 false false R31.htm 220022001 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Policies) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesPolicies Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Policies) Policies http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPolicies 31 false false R32.htm 230033001 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Tables) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesTables Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Tables) Tables http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPolicies 32 false false R33.htm 230103002 - Disclosure - Investment Securities (Tables) Sheet http://www.flagstar.com/role/InvestmentSecuritiesTables Investment Securities (Tables) Tables http://www.flagstar.com/role/InvestmentSecurities 33 false false R34.htm 230203003 - Disclosure - Loans Held-for-Investment (Tables) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentTables Loans Held-for-Investment (Tables) Tables http://www.flagstar.com/role/LoansHeldforInvestment 34 false false R35.htm 230323004 - Disclosure - Repossessed Assets (Tables) Sheet http://www.flagstar.com/role/RepossessedAssetsTables Repossessed Assets (Tables) Tables http://www.flagstar.com/role/RepossessedAssets 35 false false R36.htm 230403005 - Disclosure - Premises and Equipment (Tables) Sheet http://www.flagstar.com/role/PremisesandEquipmentTables Premises and Equipment (Tables) Tables http://www.flagstar.com/role/PremisesandEquipment 36 false false R37.htm 230443006 - Disclosure - Mortgage Servicing Rights (Tables) Sheet http://www.flagstar.com/role/MortgageServicingRightsTables Mortgage Servicing Rights (Tables) Tables http://www.flagstar.com/role/MortgageServicingRights 37 false false R38.htm 230493007 - Disclosure - Derivative Financial Instruments (Tables) Sheet http://www.flagstar.com/role/DerivativeFinancialInstrumentsTables Derivative Financial Instruments (Tables) Tables http://www.flagstar.com/role/DerivativeFinancialInstruments 38 false false R39.htm 230553008 - Disclosure - Deposit Accounts (Tables) Sheet http://www.flagstar.com/role/DepositAccountsTables Deposit Accounts (Tables) Tables http://www.flagstar.com/role/DepositAccounts 39 false false R40.htm 230593009 - Disclosure - Borrowings (Tables) Sheet http://www.flagstar.com/role/BorrowingsTables Borrowings (Tables) Tables http://www.flagstar.com/role/Borrowings 40 false false R41.htm 230663010 - Disclosure - Accumulated Other Comprehensive Income (Tables) Sheet http://www.flagstar.com/role/AccumulatedOtherComprehensiveIncomeTables Accumulated Other Comprehensive Income (Tables) Tables http://www.flagstar.com/role/AccumulatedOtherComprehensiveIncome 41 false false R42.htm 230693011 - Disclosure - Earnings Per Share (Tables) Sheet http://www.flagstar.com/role/EarningsPerShareTables Earnings Per Share (Tables) Tables http://www.flagstar.com/role/EarningsPerShare 42 false false R43.htm 230723012 - Disclosure - Stock-Based Compensation (Tables) Sheet http://www.flagstar.com/role/StockBasedCompensationTables Stock-Based Compensation (Tables) Tables http://www.flagstar.com/role/StockBasedCompensation 43 false false R44.htm 230763013 - Disclosure - Income Taxes (Tables) Sheet http://www.flagstar.com/role/IncomeTaxesTables Income Taxes (Tables) Tables http://www.flagstar.com/role/IncomeTaxes 44 false false R45.htm 230823014 - Disclosure - Regulatory Capital (Tables) Sheet http://www.flagstar.com/role/RegulatoryCapitalTables Regulatory Capital (Tables) Tables http://www.flagstar.com/role/RegulatoryCapital 45 false false R46.htm 230853015 - Disclosure - Legal Proceedings, Contingencies and Commitments (Tables) Sheet http://www.flagstar.com/role/LegalProceedingsContingenciesandCommitmentsTables Legal Proceedings, Contingencies and Commitments (Tables) Tables http://www.flagstar.com/role/LegalProceedingsContingenciesandCommitments 46 false false R47.htm 230893016 - Disclosure - Fair Value Measurements (Tables) Sheet http://www.flagstar.com/role/FairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://www.flagstar.com/role/FairValueMeasurements 47 false false R48.htm 231003017 - Disclosure - Segment Information (Tables) Sheet http://www.flagstar.com/role/SegmentInformationTables Segment Information (Tables) Tables http://www.flagstar.com/role/SegmentInformation 48 false false R49.htm 231033018 - Disclosure - Holding Company Only Financial Statements (Tables) Sheet http://www.flagstar.com/role/HoldingCompanyOnlyFinancialStatementsTables Holding Company Only Financial Statements (Tables) Tables http://www.flagstar.com/role/HoldingCompanyOnlyFinancialStatements 49 false false R50.htm 231083019 - Disclosure - Quarterly Financial Data (Unaudited) (Tables) Sheet http://www.flagstar.com/role/QuarterlyFinancialDataUnauditedTables Quarterly Financial Data (Unaudited) (Tables) Tables http://www.flagstar.com/role/QuarterlyFinancialDataUnaudited 50 false false R51.htm 240044001 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Narrative (Details) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesNarrativeDetails Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Narrative (Details) Details http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesTables 51 false false R52.htm 240054002 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Schedule of Information Relating to Operating Leases (Details) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesScheduleofInformationRelatingtoOperatingLeasesDetails Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Schedule of Information Relating to Operating Leases (Details) Details 52 false false R53.htm 240064003 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Schedule of Minimum Contractual Lease Obligations (Details) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesScheduleofMinimumContractualLeaseObligationsDetails Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Schedule of Minimum Contractual Lease Obligations (Details) Details 53 false false R54.htm 240074004 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Schedule of Disaggregation of Revenue (Details) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesScheduleofDisaggregationofRevenueDetails Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Schedule of Disaggregation of Revenue (Details) Details 54 false false R55.htm 240084005 - Disclosure - Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Impact of ASC 326 (Details) Sheet http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesImpactofASC326Details Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Impact of ASC 326 (Details) Details http://www.flagstar.com/role/DescriptionofBusinessBasisofPresentationandSummaryofSignificantAccountingPoliciesTables 55 false false R56.htm 240114006 - Disclosure - Investment Securities - Summary of Investment Securities (Details) Sheet http://www.flagstar.com/role/InvestmentSecuritiesSummaryofInvestmentSecuritiesDetails Investment Securities - Summary of Investment Securities (Details) Details 56 false false R57.htm 240124007 - Disclosure - Investment Securities - Investment Securities, Narrative (Details) Sheet http://www.flagstar.com/role/InvestmentSecuritiesInvestmentSecuritiesNarrativeDetails Investment Securities - Investment Securities, Narrative (Details) Details 57 false false R58.htm 240134008 - Disclosure - Investment Securities - Available-for-Sale Securities (Details) Sheet http://www.flagstar.com/role/InvestmentSecuritiesAvailableforSaleSecuritiesDetails Investment Securities - Available-for-Sale Securities (Details) Details 58 false false R59.htm 240144009 - Disclosure - Investment Securities - Held-to-Maturity Securities (Details) Sheet http://www.flagstar.com/role/InvestmentSecuritiesHeldtoMaturitySecuritiesDetails Investment Securities - Held-to-Maturity Securities (Details) Details 59 false false R60.htm 240154010 - Disclosure - Investment Securities - Summary of Unrealized Loss Positions on Investment Securities (Details) Sheet http://www.flagstar.com/role/InvestmentSecuritiesSummaryofUnrealizedLossPositionsonInvestmentSecuritiesDetails Investment Securities - Summary of Unrealized Loss Positions on Investment Securities (Details) Details 60 false false R61.htm 240164011 - Disclosure - Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) Sheet http://www.flagstar.com/role/InvestmentSecuritiesAmortizedCostandEstimatedFairValueofSecuritiesbyContractualMaturityDetails Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) Details 61 false false R62.htm 240184012 - Disclosure - Loans Held-for-Sale (Details) Sheet http://www.flagstar.com/role/LoansHeldforSaleDetails Loans Held-for-Sale (Details) Details http://www.flagstar.com/role/LoansHeldforSale 62 false false R63.htm 240214013 - Disclosure - Loans Held-for-Investment - Summary of Loans Held-for-Investment (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentSummaryofLoansHeldforInvestmentDetails Loans Held-for-Investment - Summary of Loans Held-for-Investment (Details) Details 63 false false R64.htm 240224014 - Disclosure - Loans Held-for-Investment - UPB of Loan Sales and Purchases in the Loans Held-for-Investment Portfolio (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentUPBofLoanSalesandPurchasesintheLoansHeldforInvestmentPortfolioDetails Loans Held-for-Investment - UPB of Loan Sales and Purchases in the Loans Held-for-Investment Portfolio (Details) Details 64 false false R65.htm 240234015 - Disclosure - Loans Held-for-Investment - Narrative (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentNarrativeDetails Loans Held-for-Investment - Narrative (Details) Details 65 false false R66.htm 240244016 - Disclosure - Loans Held-for-Investment - Changes in ALLL by Class of Loan (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentChangesinALLLbyClassofLoanDetails Loans Held-for-Investment - Changes in ALLL by Class of Loan (Details) Details 66 false false R67.htm 240254017 - Disclosure - Loans Held-for-Investment - Aging Analysis of Past Due and Current Loans (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentAgingAnalysisofPastDueandCurrentLoansDetails Loans Held-for-Investment - Aging Analysis of Past Due and Current Loans (Details) Details 67 false false R68.htm 240264018 - Disclosure - Loans Held-for-Investment - Summary of TDRs by Type and Performing Status (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentSummaryofTDRsbyTypeandPerformingStatusDetails Loans Held-for-Investment - Summary of TDRs by Type and Performing Status (Details) Details 68 false false R69.htm 240274019 - Disclosure - Loans Held-for-Investment - Summary of Newly Modified TDRs (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentSummaryofNewlyModifiedTDRsDetails Loans Held-for-Investment - Summary of Newly Modified TDRs (Details) Details 69 false false R70.htm 240284020 - Disclosure - Loans Held-for-Investment - Loan Credit Quality Indicators (Details) Sheet http://www.flagstar.com/role/LoansHeldforInvestmentLoanCreditQualityIndicatorsDetails Loans Held-for-Investment - Loan Credit Quality Indicators (Details) Details 70 false false R71.htm 240304021 - Disclosure - Loans with Government Guarantees (Details) Sheet http://www.flagstar.com/role/LoanswithGovernmentGuaranteesDetails Loans with Government Guarantees (Details) Details http://www.flagstar.com/role/LoanswithGovernmentGuarantees 71 false false R72.htm 240334022 - Disclosure - Repossessed Assets - Summary of Repossessed Assets (Details) Sheet http://www.flagstar.com/role/RepossessedAssetsSummaryofRepossessedAssetsDetails Repossessed Assets - Summary of Repossessed Assets (Details) Details 72 false false R73.htm 240344023 - Disclosure - Repossessed Assets - Activity in Repossessed Assets (Details) Sheet http://www.flagstar.com/role/RepossessedAssetsActivityinRepossessedAssetsDetails Repossessed Assets - Activity in Repossessed Assets (Details) Details 73 false false R74.htm 240364024 - Disclosure - Variable Interest Entities (Details) Sheet http://www.flagstar.com/role/VariableInterestEntitiesDetails Variable Interest Entities (Details) Details http://www.flagstar.com/role/VariableInterestEntities 74 false false R75.htm 240384025 - Disclosure - Federal Home Loan Bank Stock (Details) Sheet http://www.flagstar.com/role/FederalHomeLoanBankStockDetails Federal Home Loan Bank Stock (Details) Details http://www.flagstar.com/role/FederalHomeLoanBankStock 75 false false R76.htm 240414026 - Disclosure - Premises and Equipment - Premises and Equipment and Estimated Useful Lives (Details) Sheet http://www.flagstar.com/role/PremisesandEquipmentPremisesandEquipmentandEstimatedUsefulLivesDetails Premises and Equipment - Premises and Equipment and Estimated Useful Lives (Details) Details 76 false false R77.htm 240424027 - Disclosure - Premises and Equipment - Narrative (Details) Sheet http://www.flagstar.com/role/PremisesandEquipmentNarrativeDetails Premises and Equipment - Narrative (Details) Details 77 false false R78.htm 240454028 - Disclosure - Mortgage Servicing Rights - Schedule of Changes in the Fair Value of Residential First Mortgage MSRs (Details) Sheet http://www.flagstar.com/role/MortgageServicingRightsScheduleofChangesintheFairValueofResidentialFirstMortgageMSRsDetails Mortgage Servicing Rights - Schedule of Changes in the Fair Value of Residential First Mortgage MSRs (Details) Details 78 false false R79.htm 240464029 - Disclosure - Mortgage Servicing Rights - Summary of Adverse Changes to Weighted-Average Assumptions on the Fair Value of Servicing Rights (Details) Sheet http://www.flagstar.com/role/MortgageServicingRightsSummaryofAdverseChangestoWeightedAverageAssumptionsontheFairValueofServicingRightsDetails Mortgage Servicing Rights - Summary of Adverse Changes to Weighted-Average Assumptions on the Fair Value of Servicing Rights (Details) Details 79 false false R80.htm 240474030 - Disclosure - Mortgage Servicing Rights - Summary of Income and Fees (Details) Sheet http://www.flagstar.com/role/MortgageServicingRightsSummaryofIncomeandFeesDetails Mortgage Servicing Rights - Summary of Income and Fees (Details) Details 80 false false R81.htm 240504031 - Disclosure - Derivative Financial Instruments - Narrative (Details) Sheet http://www.flagstar.com/role/DerivativeFinancialInstrumentsNarrativeDetails Derivative Financial Instruments - Narrative (Details) Details 81 false false R82.htm 240514032 - Disclosure - Derivative Financial Instruments - Notional Amount, Estimated Fair Value and Maturity of Derivative Financial Instruments (Details) Sheet http://www.flagstar.com/role/DerivativeFinancialInstrumentsNotionalAmountEstimatedFairValueandMaturityofDerivativeFinancialInstrumentsDetails Derivative Financial Instruments - Notional Amount, Estimated Fair Value and Maturity of Derivative Financial Instruments (Details) Details 82 false false R83.htm 240524033 - Disclosure - Derivative Financial Instruments - Derivatives Subject to a Master Netting Arrangement (Details) Sheet http://www.flagstar.com/role/DerivativeFinancialInstrumentsDerivativesSubjecttoaMasterNettingArrangementDetails Derivative Financial Instruments - Derivatives Subject to a Master Netting Arrangement (Details) Details 83 false false R84.htm 240534034 - Disclosure - Derivative Financial Instruments - Net Gain (Loss) Recognized in Income on Derivative Instruments (Details) Sheet http://www.flagstar.com/role/DerivativeFinancialInstrumentsNetGainLossRecognizedinIncomeonDerivativeInstrumentsDetails Derivative Financial Instruments - Net Gain (Loss) Recognized in Income on Derivative Instruments (Details) Details 84 false false R85.htm 240564035 - Disclosure - Deposit Accounts - Summary of Deposit Accounts (Details) Sheet http://www.flagstar.com/role/DepositAccountsSummaryofDepositAccountsDetails Deposit Accounts - Summary of Deposit Accounts (Details) Details 85 false false R86.htm 240574036 - Disclosure - Deposit Accounts - Scheduled Maturities for Certificates of Deposit (Details) Sheet http://www.flagstar.com/role/DepositAccountsScheduledMaturitiesforCertificatesofDepositDetails Deposit Accounts - Scheduled Maturities for Certificates of Deposit (Details) Details 86 false false R87.htm 240604037 - Disclosure - Borrowings - Breakdown of FHLB Advances and Other Borrowings Outstanding (Details) Sheet http://www.flagstar.com/role/BorrowingsBreakdownofFHLBAdvancesandOtherBorrowingsOutstandingDetails Borrowings - Breakdown of FHLB Advances and Other Borrowings Outstanding (Details) Details 87 false false R88.htm 240614038 - Disclosure - Borrowings - Detailed Information on FHLB Advances and Other Borrowings (Details) Sheet http://www.flagstar.com/role/BorrowingsDetailedInformationonFHLBAdvancesandOtherBorrowingsDetails Borrowings - Detailed Information on FHLB Advances and Other Borrowings (Details) Details 88 false false R89.htm 240624039 - Disclosure - Borrowings - Maturity Dates of FHLB Advances and Other Borrowings (Details) Sheet http://www.flagstar.com/role/BorrowingsMaturityDatesofFHLBAdvancesandOtherBorrowingsDetails Borrowings - Maturity Dates of FHLB Advances and Other Borrowings (Details) Details 89 false false R90.htm 240634040 - Disclosure - Borrowings - Summary of Long-Term Debt, Net of Debt Issuance Costs (Details) Sheet http://www.flagstar.com/role/BorrowingsSummaryofLongTermDebtNetofDebtIssuanceCostsDetails Borrowings - Summary of Long-Term Debt, Net of Debt Issuance Costs (Details) Details 90 false false R91.htm 240644041 - Disclosure - Borrowings - Narrative (Details) Sheet http://www.flagstar.com/role/BorrowingsNarrativeDetails Borrowings - Narrative (Details) Details 91 false false R92.htm 240674042 - Disclosure - Accumulated Other Comprehensive Income (Details) Sheet http://www.flagstar.com/role/AccumulatedOtherComprehensiveIncomeDetails Accumulated Other Comprehensive Income (Details) Details http://www.flagstar.com/role/AccumulatedOtherComprehensiveIncomeTables 92 false false R93.htm 240704043 - Disclosure - Earnings Per Share - Computation of Basic and Diluted Earnings Per Share of Common Stock (Details) Sheet http://www.flagstar.com/role/EarningsPerShareComputationofBasicandDilutedEarningsPerShareofCommonStockDetails Earnings Per Share - Computation of Basic and Diluted Earnings Per Share of Common Stock (Details) Details 93 false false R94.htm 240734044 - Disclosure - Stock-Based Compensation - Narrative (Details) Sheet http://www.flagstar.com/role/StockBasedCompensationNarrativeDetails Stock-Based Compensation - Narrative (Details) Details 94 false false R95.htm 240744045 - Disclosure - Stock-Based Compensation - Summary of Restricted Stock Activity (Details) Sheet http://www.flagstar.com/role/StockBasedCompensationSummaryofRestrictedStockActivityDetails Stock-Based Compensation - Summary of Restricted Stock Activity (Details) Details 95 false false R96.htm 240774046 - Disclosure - Income Taxes - Components of the Provision (Benefit) for Income Taxes (Details) Sheet http://www.flagstar.com/role/IncomeTaxesComponentsoftheProvisionBenefitforIncomeTaxesDetails Income Taxes - Components of the Provision (Benefit) for Income Taxes (Details) Details 96 false false R97.htm 240784047 - Disclosure - Income Taxes - Summary of Differences Between the Effective Tax Rate and the Statutory Federal Tax Rate (Details) Sheet http://www.flagstar.com/role/IncomeTaxesSummaryofDifferencesBetweentheEffectiveTaxRateandtheStatutoryFederalTaxRateDetails Income Taxes - Summary of Differences Between the Effective Tax Rate and the Statutory Federal Tax Rate (Details) Details 97 false false R98.htm 240794048 - Disclosure - Income Taxes - Temporary Differences and Carryforwards Giving Rise to DTAs and Liabilities (Details) Sheet http://www.flagstar.com/role/IncomeTaxesTemporaryDifferencesandCarryforwardsGivingRisetoDTAsandLiabilitiesDetails Income Taxes - Temporary Differences and Carryforwards Giving Rise to DTAs and Liabilities (Details) Details 98 false false R99.htm 240804049 - Disclosure - Income Taxes - Narrative (Details) Sheet http://www.flagstar.com/role/IncomeTaxesNarrativeDetails Income Taxes - Narrative (Details) Details 99 false false R100.htm 240834050 - Disclosure - Regulatory Capital (Details) Sheet http://www.flagstar.com/role/RegulatoryCapitalDetails Regulatory Capital (Details) Details http://www.flagstar.com/role/RegulatoryCapitalTables 100 false false R101.htm 240864051 - Disclosure - Legal Proceedings, Contingencies and Commitments - Narrative (Details) Sheet http://www.flagstar.com/role/LegalProceedingsContingenciesandCommitmentsNarrativeDetails Legal Proceedings, Contingencies and Commitments - Narrative (Details) Details http://www.flagstar.com/role/LegalProceedingsContingenciesandCommitmentsTables 101 false false R102.htm 240874052 - Disclosure - Legal Proceedings, Contingencies and Commitments - Summary of the Contractual Amount of Significant Commitments (Details) Sheet http://www.flagstar.com/role/LegalProceedingsContingenciesandCommitmentsSummaryoftheContractualAmountofSignificantCommitmentsDetails Legal Proceedings, Contingencies and Commitments - Summary of the Contractual Amount of Significant Commitments (Details) Details 102 false false R103.htm 240904053 - Disclosure - Fair Value Measurements - Financial Instruments Carried at Fair Value (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsFinancialInstrumentsCarriedatFairValueDetails Fair Value Measurements - Financial Instruments Carried at Fair Value (Details) Details 103 false false R104.htm 240914054 - Disclosure - Fair Value Measurements - Roll Forward of Financial Instruments (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsRollForwardofFinancialInstrumentsDetails Fair Value Measurements - Roll Forward of Financial Instruments (Details) Details 104 false false R105.htm 240924055 - Disclosure - Fair Value Measurements - Quantitative Information about Recurring Level 3 Fair Value Financial Instruments (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsQuantitativeInformationaboutRecurringLevel3FairValueFinancialInstrumentsDetails Fair Value Measurements - Quantitative Information about Recurring Level 3 Fair Value Financial Instruments (Details) Details 105 false false R106.htm 240934056 - Disclosure - Fair Value Measurements - Narrative (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsNarrativeDetails Fair Value Measurements - Narrative (Details) Details 106 false false R107.htm 240944057 - Disclosure - Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsAssetsMeasuredatFairValueonaNonrecurringBasisDetails Fair Value Measurements - Assets Measured at Fair Value on a Nonrecurring Basis (Details) Details 107 false false R108.htm 240954058 - Disclosure - Fair Value Measurements - Quantitative Information about Nonrecurring Level 3 Fair Value Financial Instruments (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsQuantitativeInformationaboutNonrecurringLevel3FairValueFinancialInstrumentsDetails Fair Value Measurements - Quantitative Information about Nonrecurring Level 3 Fair Value Financial Instruments (Details) Details 108 false false R109.htm 240964059 - Disclosure - Fair Value Measurements - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsCarryingAmountandEstimatedFairValueofFinancialInstrumentsDetails Fair Value Measurements - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) Details 109 false false R110.htm 240974060 - Disclosure - Fair Value Measurements - Changes in Fair Value Included in Earnings (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsChangesinFairValueIncludedinEarningsDetails Fair Value Measurements - Changes in Fair Value Included in Earnings (Details) Details 110 false false R111.htm 240984061 - Disclosure - Fair Value Measurements - Differences Between Aggregate Fair Value and Aggregate Remaining Contractual Principal Balance Outstanding (Details) Sheet http://www.flagstar.com/role/FairValueMeasurementsDifferencesBetweenAggregateFairValueandAggregateRemainingContractualPrincipalBalanceOutstandingDetails Fair Value Measurements - Differences Between Aggregate Fair Value and Aggregate Remaining Contractual Principal Balance Outstanding (Details) Details 111 false false R112.htm 241014062 - Disclosure - Segment Information (Details) Sheet http://www.flagstar.com/role/SegmentInformationDetails Segment Information (Details) Details http://www.flagstar.com/role/SegmentInformationTables 112 false false R113.htm 241044063 - Disclosure - Holding Company Only Financial Statements - Condensed Unconsolidated Statements of Financial Condition (Details) Sheet http://www.flagstar.com/role/HoldingCompanyOnlyFinancialStatementsCondensedUnconsolidatedStatementsofFinancialConditionDetails Holding Company Only Financial Statements - Condensed Unconsolidated Statements of Financial Condition (Details) Details 113 false false R114.htm 241054064 - Disclosure - Holding Company Only Financial Statements - Condensed Unconsolidated Statements of Operations (Details) Sheet http://www.flagstar.com/role/HoldingCompanyOnlyFinancialStatementsCondensedUnconsolidatedStatementsofOperationsDetails Holding Company Only Financial Statements - Condensed Unconsolidated Statements of Operations (Details) Details 114 false false R115.htm 241064065 - Disclosure - Holding Company Only Financial Statements - Condensed Unconsolidated Statements of Cash Flow (Details) Sheet http://www.flagstar.com/role/HoldingCompanyOnlyFinancialStatementsCondensedUnconsolidatedStatementsofCashFlowDetails Holding Company Only Financial Statements - Condensed Unconsolidated Statements of Cash Flow (Details) Details 115 false false R116.htm 241094066 - Disclosure - Quarterly Financial Data (Unaudited) (Details) Sheet http://www.flagstar.com/role/QuarterlyFinancialDataUnauditedDetails Quarterly Financial Data (Unaudited) (Details) Details http://www.flagstar.com/role/QuarterlyFinancialDataUnauditedTables 116 false false All Reports Book All Reports fbc-20201231.htm a20201231exhibit1012.htm a20201231exhibit23.htm a20201231exhibit311.htm a20201231exhibit312.htm a20201231exhibit321.htm a20201231exhibit322.htm a20201231exhibit44.htm a20202131exhibit21.htm fbc-20201231.xsd fbc-20201231_cal.xml fbc-20201231_def.xml fbc-20201231_lab.xml fbc-20201231_pre.xml fbc-20201231_g1.jpg fbc-20201231_g2.jpg http://fasb.org/us-gaap/2020-01-31 http://fasb.org/srt/2020-01-31 http://xbrl.sec.gov/dei/2020-01-31 true true