Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
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	$ 86,000,000
Outstanding principal balances of commercial mortgage servicing rights obtained from Bayview Financial	3,700,000,000		3,800,000,000
Amounts recorded as capitalized servicing assets for commercial mortgage loans	7,000,000		8,000,000
Servicing rights purchased from Bayview Financial related to residential mortgage loans	2,000,000		2,000,000
Outstanding principal balances of residential mortgage loans from Bayview Financial	2,600,000,000		2,700,000,000
Revenues from servicing residential and small balance commercial mortgage loans purchased from BLG and Bayview Financial	8,000,000	10,000,000
Collateralized mortgage obligations in available-for-sale investment securities portfolio securitized by Bayview Financial	8,000,000		11,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	237,000,000		242,000,000
Bayview and Colonial [Member]
Schedule Of Equity Method Investments Joint Ventures [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	10,900,000,000		11,400,000,000
Revenues from servicing residential and small balance commercial mortgage loans purchased from BLG and Bayview Financial	$ 2,000,000	$ 2,000,000