Investment Securities (Details 1) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Changes in credit losses associated with debt securities for which other than temporary impairment losses
Beginning balance	$ 298,141	$ 314,263	$ 327,912	$ 284,513
Additions for credit losses not previously recognized	9,642	9,532	52,213	46,721
Reductions for increases in cash flows	(90)	(108)	(5,110)	(450)
Reductions for bond charge-offs	(23,127)	(11,812)	(90,449)	(18,909)
Ending balance	$ 284,566	$ 311,875	$ 284,566	$ 311,875