Changes of Unamortized Discount and Designated Credit Reserves on AFS Securities (Detail) (USD $) In Thousands			3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Residential	Jun. 30, 2011 Residential	Jun. 30, 2011 Commercial	Jun. 30, 2011 Commercial	Jun. 30, 2011 CDO	Jun. 30, 2011 CDO
Credit Reserve
Beginning balance	$ 300,666	$ 463,222	$ 280,478	$ 297,849	$ 64,717	$ 76,979	$ 29,505	$ 88,394
Amortization of net (discount) premium
Realized credit losses			(34,091)	(56,265)	(16,655)	(25,952)		(3,005)
Acquisitions			28	1,176
Sales, calls, other			(11,543)	(20,188)		(2,653)	(18,751)	(74,662)
Impairments			929	2,636	536	892		560
Transfers to (release of) credit reserves			5,098	15,691	389	(279)	26	(507)
Ending Balance	300,666	463,222	240,899	240,899	48,987	48,987	10,780	10,780
Unamortized Discount Net
Beginning balance	249,107	285,199	259,469	291,093	4,784	5,591	520	(11,485)
Amortization of net (discount) premium			(10,497)	(22,464)	(33)	(69)	18	(85)
Realized credit losses
Acquisitions			9,112	11,601
Sales, calls, other			(9,324)	(20,877)		(1,439)	571	12,146
Impairments
Transfers to (release of) credit reserves			(5,098)	(15,691)	(389)	279	(26)	507
Ending Balance	$ 249,107	$ 285,199	$ 243,662	$ 243,662	$ 4,362	$ 4,362	$ 1,083	$ 1,083