Investment Securities (Details 2) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses less than 12 months	$ (1,797)	$ (41,910)
Unrealized losses 12 months or more	(1,700)	(3,914)
Total unrealized losses	(3,497)	(45,824)
Fair value of unrealized losses less than 12 months	470,130	2,174,784
Fair value of unrealized losses 12 months or more	6,366	46,713
Fair value of total unrealized losses	476,496	2,221,497
Federal agency securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses less than 12 months		(25)
Unrealized losses 12 months or more		0
Total unrealized losses		(25)
Fair value of unrealized losses less than 12 months		29,716
Fair value of unrealized losses 12 months or more		0
Fair value of total unrealized losses		29,716
Obligations of state and political subdivisions [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses less than 12 months	(308)	(4,983)
Unrealized losses 12 months or more	(363)	(367)
Total unrealized losses	(671)	(5,350)
Fair value of unrealized losses less than 12 months	22,384	237,902
Fair value of unrealized losses 12 months or more	3,042	2,543
Fair value of total unrealized losses	25,426	240,445
Residential mortgage-related securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses less than 12 months	(982)	(36,280)
Unrealized losses 12 months or more	(29)	(2,234)
Total unrealized losses	(1,011)	(38,514)
Fair value of unrealized losses less than 12 months	191,159	1,613,498
Fair value of unrealized losses 12 months or more	2,505	43,306
Fair value of total unrealized losses	193,664	1,656,804
Asset-backed securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses less than 12 months	(465)	(621)
Unrealized losses 12 months or more	0	0
Total unrealized losses	(465)	(621)
Fair value of unrealized losses less than 12 months	221,959	293,568
Fair value of unrealized losses 12 months or more	0	0
Fair value of total unrealized losses	221,959	293,568
Other securities (debt and equity) [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses less than 12 months	(42)	(1)
Unrealized losses 12 months or more	(1,308)	(1,313)
Total unrealized losses	(1,350)	(1,314)
Fair value of unrealized losses less than 12 months	34,628	100
Fair value of unrealized losses 12 months or more	819	864
Fair value of total unrealized losses	$ 35,447	$ 964