Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Available for sale securities continuous unrealized loss position fair value and unrealized losses
Total temporarily impaired securities, Less than 12 Months, Fair Value	$ 263,487	$ 234,315
Total Temporarily Impaired Securities, Less than 12 Months, Unrealized Losses	(2,318)	(1,811)
Securities with unrealized losses,12 months or longer, Fair Value	26,321	13,939
Total Temporarily Impaired Securities, 12 months or longer, Unrealized Losses	(346)	(185)
Total Temporarily Impaired Securities, 12 months or longer, Fair Value	289,808	248,254
Total Temporarily Impaired Securities Continuous Unrealized Losses Position Unrealized Losses	(2,664)	(1,996)
Mortgage-backed securities of U.S Government Sponsored Entities [Member]
Available for sale securities continuous unrealized loss position fair value and unrealized losses
Less than 12 Months, Fair Value	46,580	54,289
Less than 12 Months, Unrealized Losses	(658)	(469)
12 Months or Longer, Fair Value	17,898	0
12 Months or Longer, Unrealized Losses	(246)	0
Fair Value, Total	64,478	54,289
Aggregate Losses	(904)	(469)
Collateralized mortgage obligations of U.S. Government Sponsored Entities [Member]
Available for sale securities continuous unrealized loss position fair value and unrealized losses
12 Months or Longer, Fair Value	0	4,593
12 Months or Longer, Unrealized Losses	0	(93)
Securities with unrealized losses,12 months or longer, Fair Value	188,789	154,650
Securities with unrealized losses, Less than 12 months, Fair Value	188,789	150,057
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Aggregate Losses	(1,219)	(994)
Available for Sale and Held to Maturity Securities Continuous Unrealized Loss Position Less than 12 Months Aggregate Losses	(1,219)	(901)
Private collateralized mortgage obligations [Member]
Available for sale securities continuous unrealized loss position fair value and unrealized losses
Less than 12 Months, Fair Value	28,118	29,969
Less than 12 Months, Unrealized Losses	(441)	(441)
12 Months or Longer, Fair Value	8,298	9,221
12 Months or Longer, Unrealized Losses	(98)	(89)
Fair Value, Total	36,416	39,190
Aggregate Losses	(539)	(530)
Obligations of state and political subdivisions [Member]
Available for sale securities continuous unrealized loss position fair value and unrealized losses
Less than 12 Months, Fair Value	0	0
Less than 12 Months, Unrealized Losses	0	0
12 Months or Longer, Fair Value	125	125
12 Months or Longer, Unrealized Losses	(2)	(3)
Fair Value, Total	125	125
Aggregate Losses	$ (2)	$ (3)