Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 7,002,524,000		$ 7,002,524,000		$ 8,444,914,000
Bayview Lending Group [Member]
Schedule of Equity Method Investments [Line Items]
Minority interest in Bayview Lending Group LLC	20.00%		20.00%
Carrying value of minority interest investment in Bayview Lending Group LLC	$ 0		$ 0
Bayview Lending Group [Member] | Other Revenues From Operations [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	0	$ 0	37,000,000	$ 24,000,000
Bayview Lending Group and Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	2,300,000,000		2,300,000,000		2,500,000,000
Revenue from contract with customer	3,000,000	4,000,000	9,000,000	11,000,000
Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	65,100,000,000		65,100,000,000		56,800,000,000
Revenues from sub-servicing	33,000,000	$ 28,000,000	90,000,000	$ 86,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	100,000,000		100,000,000		$ 113,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	714,000,000		714,000,000
Bayview Financial [Member] | Syndicated Loan Facility [Member] | M&T Bank [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 90,000,000		$ 90,000,000