Relationship with BLG and Bayview Financial (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Schedule of Equity Method Investments [Line Items]
Revenue from contract with customer	$ 423,000,000	$ 394,000,000	$ 1,237,000,000	$ 1,149,000,000
Deposits	163,426,000,000		163,426,000,000		$ 161,095,000,000
Bayview Financial
Schedule of Equity Method Investments [Line Items]
Deposits	$ 4,400,000,000		$ 4,400,000,000		2,200,000,000
Bayview Lending Group
Schedule of Equity Method Investments [Line Items]
Ownership percentage (as a percent)	20.00%		20.00%
Equity method investments	$ 0		$ 0
Bayview Lending Group | Other Revenues From Operations
Schedule of Equity Method Investments [Line Items]
Income from equity method investments		20,000,000	20,000,000	25,000,000
Bayview Lending Group and Bayview Financial
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	907,000,000		907,000,000		1,000,000,000.0
Revenue from contract with customer	1,000,000	1,000,000	3,000,000	4,000,000
Bayview Financial
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	161,800,000,000		161,800,000,000		111,500,000,000
Revenues from sub-servicing	64,000,000	$ 29,000,000	159,000,000	$ 92,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	33,000,000		33,000,000		37,000,000
Commitments to extend credit	1,000,000,000.0		1,000,000,000.0
Outstanding balance	$ 635,000,000		$ 635,000,000		$ 404,000,000