Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Bayview Lending Group and Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	$ 4,300		$ 4,300		$ 4,800
Revenues from servicing	$ 6	$ 6	$ 17	$ 20
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	$ 33		$ 33
Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Revenues from servicing	26	$ 29	91	$ 82
Outstanding principal balances of residential mortgage loans from Bayview Financial	39,500		39,500		41,300
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	$ 187		$ 187		$ 202