Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 item	Dec. 31, 2012 item
Number of Securities
Unrealized loss for less than twelve months	253	256
Total	253	256
Fair Value
Unrealized loss for less than twelve months	$ 812,441	$ 446,562
Estimated Fair Value, Total	812,441	446,562
Unrealized Loss
Unrealized loss for less than twelve months	48,478	2,603
Total	48,478	2,603
U.S. Treasury securities
Number of Securities
Unrealized loss for less than twelve months	4	2
Total	4	2
Fair Value
Unrealized loss for less than twelve months	17,709	2,427
Estimated Fair Value, Total	17,709	2,427
Unrealized Loss
Unrealized loss for less than twelve months	17	2
Total	17	2
Bonds
Number of Securities
Unrealized loss for less than twelve months	38	14
Total	38	14
Fair Value
Unrealized loss for less than twelve months	560,938	236,305
Estimated Fair Value, Total	560,938	236,305
Unrealized Loss
Unrealized loss for less than twelve months	37,491	314
Total	37,491	314
Residential mortgage-backed securities
Number of Securities
Unrealized loss for less than twelve months	5	7
Total	5	7
Fair Value
Unrealized loss for less than twelve months	11,735	12,279
Estimated Fair Value, Total	11,735	12,279
Unrealized Loss
Unrealized loss for less than twelve months	499	70
Total	499	70
Collateralized mortgage obligations
Number of Securities
Unrealized loss for less than twelve months	9	8
Total	9	8
Fair Value
Unrealized loss for less than twelve months	78,896	38,887
Estimated Fair Value, Total	78,896	38,887
Unrealized Loss
Unrealized loss for less than twelve months	2,749	79
Total	2,749	79
Corporate debt securities
Number of Securities
Unrealized loss for less than twelve months	4
Total	4
Fair Value
Unrealized loss for less than twelve months	4,671
Estimated Fair Value, Total	4,671
Unrealized Loss
Unrealized loss for less than twelve months	276
Total	276
States and political subdivisions
Number of Securities
Unrealized loss for less than twelve months	192	225
Total	192	225
Fair Value
Unrealized loss for less than twelve months	127,377	156,664
Estimated Fair Value, Total	127,377	156,664
Unrealized Loss
Unrealized loss for less than twelve months	6,493	2,138
Total	6,493	2,138
Warrant
Number of Securities
Unrealized loss for less than twelve months	1
Total	1
Fair Value
Unrealized loss for less than twelve months	11,115
Estimated Fair Value, Total	11,115
Unrealized Loss
Unrealized loss for less than twelve months	953
Total	$ 953