Borrowed Funds - Junior Subordinated Debentures (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2023	Dec. 31, 2022
Debt Instrument
Junior Subordinated Debentures Amount Outstanding (3)	$ 578	$ 575
Capital Securities Amount Outstanding	589
Junior Subordinated Notes, Excluding Adjustments	609
Fair value adjustments, business combination	$ (31)
New York Community Capital Trust V (BONUSES Units)
Debt Instrument
Interest Rate of Capital Securities and Debentures	600.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 147
Capital Securities Amount Outstanding	$ 141
New York Community Capital Trust X
Debt Instrument
Interest Rate of Capital Securities and Debentures	727.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 124
Capital Securities Amount Outstanding	$ 120
PennFed Capital Trust III
Debt Instrument
Interest Rate of Capital Securities and Debentures	892.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 31
Capital Securities Amount Outstanding	$ 30
New York Community Capital Trust XI
Debt Instrument
Interest Rate of Capital Securities and Debentures	731.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 59
Capital Securities Amount Outstanding	$ 58
Flagstar Statutory Trust II
Debt Instrument
Interest Rate of Capital Securities and Debentures	891.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust III
Debt Instrument
Interest Rate of Capital Securities and Debentures	882.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust IV
Debt Instrument
Interest Rate of Capital Securities and Debentures	891.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust V
Debt Instrument
Interest Rate of Capital Securities and Debentures	757.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust VI
Debt Instrument
Interest Rate of Capital Securities and Debentures	757.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust VII
Debt Instrument
Interest Rate of Capital Securities and Debentures	742.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 51
Capital Securities Amount Outstanding	$ 50
Flagstar Statutory Trust VIII
Debt Instrument
Interest Rate of Capital Securities and Debentures	707.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust IX
Debt Instrument
Interest Rate of Capital Securities and Debentures	712.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust X
Debt Instrument
Interest Rate of Capital Securities and Debentures	817.00%
Junior Subordinated Debentures Amount Outstanding (3)	$ 15
Capital Securities Amount Outstanding	$ 15

Junior Subordinated Notes, Excluding Adjustments

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This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to financial liabilities assumed in connection with a business combination for which the initial accounting was incomplete.

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Value of capital units or capital shares. This element is relevant to issuers of face-amount certificates and registered investment companies.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

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