Changes in Residential and Securitized Mortgage Servicing Rights (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended				9 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Mortgage Servicing Rights Residential		Sep. 30, 2011 Mortgage Servicing Rights Residential		Sep. 30, 2012 Mortgage Servicing Rights Residential		Sep. 30, 2011 Mortgage Servicing Rights Residential		Sep. 30, 2012 Securitized Mortgage Servicing Rights	Sep. 30, 2011 Securitized Mortgage Servicing Rights	Sep. 30, 2012 Securitized Mortgage Servicing Rights	Sep. 30, 2011 Securitized Mortgage Servicing Rights
Finite-Lived Intangible Assets [Line Items]
Carrying value, beginning of period	$ 122,530	$ 117,012	$ 136,176		$ 126,771		$ 116,416		$ 106,186		$ 386	$ 886	$ 596	$ 1,192
Additions			28,178		13,200		85,977		50,519
Due to changes in valuation assumptions			(23,720)		(32,547)		(31,255)		(32,547)
Due to other changes			(18,394)	[1]	(12,410)	[1]	(48,898)	[1]	(29,144)	[1]
Amortization											(96)	(145)	(306)	(451)
Carrying value, end of period	$ 122,530	$ 117,012	$ 122,240		$ 95,014		$ 122,240		$ 95,014		$ 290	$ 741	$ 290	$ 741

[1] Includes net servicing cash flows and the passage of time.