Securities (Details 4) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value	$ 48,273	$ 530,697
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	376	3,000
Available for sale securities, Losses 12 months or longer, Fair value	871	339
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	8	6
Available for sale securities, Total, Fair value	49,144	531,036
Available for sale securities, Total, Gross Unrealized Losses	384	3,006
U.S. Treasury [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses
Available for sale securities, Losses 12 months or longer, Fair value
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses
Available for sale securities, Total, Fair value
Available for sale securities, Total, Gross Unrealized Losses
U.S. government agencies [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses
Available for sale securities, Losses 12 months or longer, Fair value
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses
Available for sale securities, Total, Fair value
Available for sale securities, Total, Gross Unrealized Losses
Municipal obligations [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value	8,992	18,854
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	35	42
Available for sale securities, Losses 12 months or longer, Fair value	569
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	3
Available for sale securities, Total, Fair value	9,561	18,854
Available for sale securities, Total, Gross Unrealized Losses	38	42
Mortgage-backed securities [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value	39,066	212,900
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	333	692
Available for sale securities, Losses 12 months or longer, Fair value	300	337
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	3	4
Available for sale securities, Total, Fair value	39,366	213,237
Available for sale securities, Total, Gross Unrealized Losses	336	696
Collateralized mortgage obligations [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value		296,860
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses		2,193
Available for sale securities, Losses 12 months or longer, Fair value
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses
Available for sale securities, Total, Fair value		296,860
Available for sale securities, Total, Gross Unrealized Losses		2,193
Other debt securities [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value		398
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses		34
Available for sale securities, Losses 12 months or longer, Fair value
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses
Available for sale securities, Total, Fair value		398
Available for sale securities, Total, Gross Unrealized Losses		34
Equity securities [Member]
Available for sale securities unrealized losses
Available for sale securities, Losses less than 12 months, Fair Value	215	1,685
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	8	39
Available for sale securities, Losses 12 months or longer, Fair value	2	2
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	2	2
Available for sale securities, Total, Fair value	217	1,687
Available for sale securities, Total, Gross Unrealized Losses	$ 10	$ 41