Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 3,459,336,000		$ 3,459,336,000		$ 3,485,369,000
Bayview Lending Group [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value of minority interest investment in Bayview Lending Group LLC	$ 0		$ 0
Minority interest in Bayview Lending Group LLC	20.00%		20.00%
Bayview Lending Group [Member] | Other Revenues From Operations [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	$ 0		$ 30,000,000	$ 0
Bayview Lending Group and Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	1,400,000,000		1,400,000,000		1,600,000,000
Revenue from contract with customer	3,000,000	$ 2,000,000	7,000,000	7,000,000
Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	81,200,000,000		81,200,000,000		74,700,000,000
Revenues from sub-servicing	33,000,000	$ 39,000,000	119,000,000	$ 110,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	52,000,000		52,000,000		62,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	2,000,000,000.0		2,000,000,000.0		1,400,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member] | M&T Bank [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 298,000,000		$ 298,000,000		$ 210,000,000