Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Jul. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 3,017,363,000			$ 3,017,363,000			$ 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	1,500,000,000			$ 1,500,000,000			1,600,000,000
Revenue from contract with customer	2,000,000		$ 2,000,000	4,000,000	4,000,000
Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	79,000,000,000.0			79,000,000,000.0			74,700,000,000
Revenues from sub-servicing	44,000,000		$ 37,000,000	86,000,000	$ 71,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	55,000,000			55,000,000			$ 62,000,000
Bayview Financial [Member] | Residential Mortgage Loans [Member] | Oceanview Dispositions, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Conventional mortgage loans	191,000,000			191,000,000
Mortgage loans on real estate principal amount of loans	184,000,000			184,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	1,500,000,000			1,500,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member] | Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount						$ 2,000,000,000.0
Bayview Financial [Member] | Syndicated Loan Facility [Member] | M&T Bank [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 247,000,000			$ 247,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member] | M&T Bank [Member] | Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount						$ 289,000,000