Investment Securities (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012 securities	Dec. 31, 2011 securities	Jun. 30, 2011 securities
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	$ 130,750	$ 148,345	$ 321,262
Unrealized Losses, Less than 12 months	(679)	(506)	(1,719)
Number of Impaired Securities, Less than 12 months	46,000	26,000	45,000
Fair Value, 12 months or longer	48,087	44,385	51,560
Unrealized Losses, 12 months or longer	(13,429)	(17,256)	(10,764)
Number of Impaired Securities, 12 months or longer	9,000	10,000	11,000
Fair Value, Total	178,837	192,730	372,822
Unrealized Losses, Total	(14,108)	(17,762)	(12,483)
US Government Agencies Debt Securities [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	0		23,538
Unrealized Losses, Less than 12 months	0		148
Number of Impaired Securities, Less than 12 months	0		2,000
Fair Value, 12 months or longer	0		0
Unrealized Losses, 12 months or longer	0		0
Number of Impaired Securities, 12 months or longer	0		0
Fair Value, Total	0		23,538
Unrealized Losses, Total	0		148
US States and Political Subdivisions Debt Securities [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	15,742	5,249	18,176
Unrealized Losses, Less than 12 months	200	50	158
Number of Impaired Securities, Less than 12 months	28,000	6,000	24,000
Fair Value, 12 months or longer	0	0	655
Unrealized Losses, 12 months or longer	0	0	23
Number of Impaired Securities, 12 months or longer	0	0	1,000
Fair Value, Total	15,742	5,249	18,831
Unrealized Losses, Total	200	50	181
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	30	40,020	14,229
Unrealized Losses, Less than 12 months	0	129	87
Number of Impaired Securities, Less than 12 months	2,000	4,000	1,000
Fair Value, 12 months or longer	0	149	182
Unrealized Losses, 12 months or longer	0	2	3
Number of Impaired Securities, 12 months or longer	0	1,000	2,000
Fair Value, Total	30	40,169	14,411
Unrealized Losses, Total	0	131	90
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	5,137
Unrealized Losses, Less than 12 months	20
Number of Impaired Securities, Less than 12 months	1,000
Fair Value, 12 months or longer	0
Unrealized Losses, 12 months or longer	0
Number of Impaired Securities, 12 months or longer	0
Fair Value, Total	5,137
Unrealized Losses, Total	20
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	88,482	48,003	265,319
Unrealized Losses, Less than 12 months	326	55	1,326
Number of Impaired Securities, Less than 12 months	9,000	6,000	18,000
Fair Value, 12 months or longer	0	0	0
Unrealized Losses, 12 months or longer	0	0	0
Number of Impaired Securities, 12 months or longer	0	0	0
Fair Value, Total	88,482	48,003	265,319
Unrealized Losses, Total	326	55	1,326
Non-agency [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	0	0
Unrealized Losses, Less than 12 months	0	0
Number of Impaired Securities, Less than 12 months	0	0
Fair Value, 12 months or longer	2	2
Unrealized Losses, 12 months or longer	0	0
Number of Impaired Securities, 12 months or longer	1,000	1,000
Fair Value, Total	2	2
Unrealized Losses, Total	0	0
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	0	30,227
Unrealized Losses, Less than 12 months	0	145
Number of Impaired Securities, Less than 12 months	0	2,000
Fair Value, 12 months or longer	0	0
Unrealized Losses, 12 months or longer	0	0
Number of Impaired Securities, 12 months or longer	0	0
Fair Value, Total	0	30,227
Unrealized Losses, Total	0	145
Corporate Debt Securities [Member]
Gross unrealized losses and fair value of securities
Fair Value, Less than 12 months	21,359	24,846	0
Unrealized Losses, Less than 12 months	133	127	0
Number of Impaired Securities, Less than 12 months	6,000	8,000	0
Fair Value, 12 months or longer	48,085	44,234	50,723
Unrealized Losses, 12 months or longer	13,429	17,254	10,738
Number of Impaired Securities, 12 months or longer	8,000	8,000	8,000
Fair Value, Total	69,444	69,080	50,723
Unrealized Losses, Total	$ 13,562	$ 17,381	$ 10,738