Investment Securities (Details 3) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	$ 840,819	$ 180,622
Unrealized Losses, Less than 12 months	(6,209)	(12,859)
Estimated fair value, 12 months or more	989,628	1,180,395
Unrealized Losses, 12 months or more	(241,872)	(298,878)
U.S. Treasury and federal agencies [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	1,903	27,289
Unrealized Losses, Less than 12 months	(2)	(18)
Estimated fair value, 12 months or more	0	0
Unrealized Losses, 12 months or more	0	0
Obligations of states and political subdivisions [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	1,444	3,712
Unrealized Losses, Less than 12 months	(6)	(18)
Estimated fair value, 12 months or more	2,323	2,062
Unrealized Losses, 12 months or more	(33)	(39)
Government issued or guaranteed [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	632,513	68,507
Unrealized Losses, Less than 12 months	(2,937)	(1,079)
Estimated fair value, 12 months or more	3,010	2,965
Unrealized Losses, 12 months or more	(44)	(32)
Privately issued residential [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	146,893	61,192
Unrealized Losses, Less than 12 months	(1,859)	(1,054)
Estimated fair value, 12 months or more	859,930	1,057,315
Unrealized Losses, 12 months or more	(209,407)	(251,027)
Privately issued commercial [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	0	0
Unrealized Losses, Less than 12 months	0	0
Estimated fair value, 12 months or more	17,233	22,407
Unrealized Losses, 12 months or more	(3,861)	(2,950)
Collateralized Debt Obligations [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	3,039	12,462
Unrealized Losses, Less than 12 months	(19)	(6,959)
Estimated fair value, 12 months or more	5,544	6,004
Unrealized Losses, 12 months or more	(1,448)	(2,119)
Other Debt Securities [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	51,652	2,134
Unrealized Losses, Less than 12 months	(935)	(10)
Estimated fair value, 12 months or more	101,588	88,969
Unrealized Losses, 12 months or more	(27,079)	(37,990)
Equity Securities [Member]
Investment Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Estimated fair value, Less than 12 months	3,375	5,326
Unrealized Losses, Less than 12 months	(451)	(3,721)
Estimated fair value, 12 months or more	0	673
Unrealized Losses, 12 months or more	$ 0	$ (4,721)