Relationship with BLG and Bayview Financial - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 8,201,000,000	$ 3,965,000,000
Bayview Lending Group [Member]
Schedule of Equity Method Investments [Line Items]
Minority interest in Bayview Lending Group LLC	20.00%
Carrying value of minority interest investment in Bayview Lending Group LLC	$ 0
Bayview Lending Group [Member] | Other Revenues From Operations [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	20,000,000	30,000,000	$ 30,000,000
Bayview Lending Group and Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	1,200,000,000	1,400,000,000
Revenue from contract with customer	6,000,000	8,000,000	9,000,000
Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	115,300,000,000	96,000,000,000
Revenues from sub-servicing	125,000,000	154,000,000	153,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	42,000,000	$ 50,000,000
FHA gauranteed purchase amount of deliquent loan			1,000,000,000
Bayview Financial [Member] | FHA Guaranteed Mortgage Loans [Member]
Schedule of Equity Method Investments [Line Items]
FHA gauranteed mortgage loan			$ 965,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	3,200,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member] | M&T Bank [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 672,000,000