Securities Securities Losses (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 350,292	$ 151,824
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	(3,444)	(2,321)
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	58,844	90,587
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	(3,973)	(4,709)
Securities Continuous Unrealized Loss Position, Fair Value, Total	409,136	242,411
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	(7,417)	(7,030)
U.S. Government Corporations and Agencies
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	0	0
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	0	0
Securities Continuous Unrealized Loss Position, Fair Value, Total	0	0
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	0	0
Mortgage-Backed Securities
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	266,527	133,538
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	(2,007)	(1,794)
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	41,396	71,231
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	(1,918)	(3,203)
Securities Continuous Unrealized Loss Position, Fair Value, Total	307,923	204,769
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	(3,925)	(4,997)
Obligations of States and Political Subdivisions
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	78,889	13,139
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	(923)	(284)
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,906	4,010
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	(423)	(689)
Securities Continuous Unrealized Loss Position, Fair Value, Total	81,795	17,149
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	(1,346)	(973)
Corporate Debt Securities
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	4,876	5,147
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	(514)	(243)
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	14,542	15,346
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	(1,632)	(817)
Securities Continuous Unrealized Loss Position, Fair Value, Total	19,418	20,493
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	(2,146)	(1,060)
Debt Securities
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	350,292	151,824
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	(3,444)	(2,321)
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	58,844	90,587
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	(3,973)	(4,709)
Securities Continuous Unrealized Loss Position, Fair Value, Total	409,136	242,411
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	(7,417)	(7,030)
Equity Securities
Gain (Loss) on Investments [Line Items]
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Securities Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	0	0
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Securities Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	0	0
Securities Continuous Unrealized Loss Position, Fair Value, Total	0	0
Securities Continuous Unrealized Loss Position, Unrealized Losses, Total	$ 0	$ 0