Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Minority interest in Bayview Lending Group LLC		20.00%
Carrying value of minority interest investment in Bayview Lending Group LLC	$ 115,000,000	$ 93,000,000	$ 115,000,000
Total other-than-temporary impairment ("OTTI") losses	79,000,000		79,000,000
Outstanding principal balances of commercial mortgage servicing rights obtained from Bayview Financial	4,400,000,000	3,800,000,000	4,400,000,000
Amounts recorded as capitalized servicing assets for commercial mortgage loans	16,000,000	8,000,000	16,000,000
Servicing rights purchased from Bayview Financial related to residential mortgage loans	5,000,000	2,000,000	5,000,000
Outstanding principal balances of residential mortgage loans from Bayview Financial	3,100,000,000	2,700,000,000	3,100,000,000
Revenues from servicing residential and small balance commercial mortgage loans purchased from BLG and Bayview Financial		35,000,000	41,000,000	46,000,000
Collateralized mortgage obligations in available-for-sale investment securities portfolio securitized by Bayview Financial	15,000,000	11,000,000	15,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	269,000,000	242,000,000	269,000,000
Bayview and Colonial [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	13,100,000,000	11,400,000,000	13,100,000,000
Revenues from servicing residential and small balance commercial mortgage loans purchased from BLG and Bayview Financial		$ 9,000,000	$ 0