Borrowed Funds - Junior Subordinated Debentures (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2025	Dec. 31, 2024
Debt Instrument
Capital Securities Amount Outstanding	$ 590
Flagstar Bancorp
Debt Instrument
Fair value adjustments, business combination	(26)
As Initially Reported
Debt Instrument
Junior subordinated debentures	$ 610	$ 610
New York Community Capital Trust V (BONUSES Units)
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.00%
Junior subordinated debentures	$ 148
Capital Securities Amount Outstanding	$ 141
New York Community Capital Trust X
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.18%
Junior subordinated debentures	$ 124
Capital Securities Amount Outstanding	$ 120
PennFed Capital Trust III
Debt Instrument
Interest Rate of Capital Securities and Debentures	7.83%
Junior subordinated debentures	$ 31
Capital Securities Amount Outstanding	$ 31
New York Community Capital Trust XI
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.21%
Junior subordinated debentures	$ 59
Capital Securities Amount Outstanding	$ 58
Flagstar Statutory Trust II
Debt Instrument
Interest Rate of Capital Securities and Debentures	7.81%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust III
Debt Instrument
Interest Rate of Capital Securities and Debentures	7.77%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust IV
Debt Instrument
Interest Rate of Capital Securities and Debentures	7.81%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust V
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.52%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust VI
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.52%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust VII
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.33%
Junior subordinated debentures	$ 51
Capital Securities Amount Outstanding	$ 50
Flagstar Statutory Trust VIII
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.02%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust IX
Debt Instrument
Interest Rate of Capital Securities and Debentures	6.03%
Junior subordinated debentures	$ 26
Capital Securities Amount Outstanding	$ 25
Flagstar Statutory Trust X
Debt Instrument
Interest Rate of Capital Securities and Debentures	7.08%
Junior subordinated debentures	$ 15
Capital Securities Amount Outstanding	$ 15

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

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Amount that would be paid, determined under the conditions specified in the contract, if the holder of the share has the right to redeem the shares.

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