Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Revenue from contract with customer	$ 394,000,000	$ 360,000,000	$ 1,149,000,000	$ 1,119,000,000
Loan facility carrying amount	$ 11,583,000,000		$ 11,583,000,000		$ 8,201,000,000
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			25,000,000	20,000,000
Bayview Lending Group and Bayview Financial
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	1,100,000,000		1,100,000,000		1,200,000,000
Revenue from contract with customer	1,000,000	1,000,000	4,000,000	5,000,000
Bayview Financial
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	112,700,000,000		112,700,000,000		115,300,000,000
Revenues from sub-servicing	29,000,000	$ 30,000,000	92,000,000	$ 94,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	38,000,000		38,000,000		$ 42,000,000
Bayview Financial | Syndicated Loan Facility
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	3,000,000,000.0		3,000,000,000.0
Bayview Financial | Syndicated Loan Facility | M&T Bank
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 510,000,000		$ 510,000,000