Offsetting Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Offsetting Assets and Liabilities [Abstract]
Derivative Asset, Fair Value, Gross Asset	$ 1,089	$ 2,148
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	1,089	2,148
derivative collateral obligation to return securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value	1,089	2,148
Securities Sold Under Agreements to Repurchase, Gross	527,925	586,867
securities sold under agreements to repurchase asset	0	0
Securities Sold Under Agreements to Repurchase, Total	527,925	586,867
Securities Sold Under Agreements to Repurchase, Collateral, Right to Reclaim Securities	527,925	586,867
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	0	0
Securities Sold Under Agreements to Repurchase, Amount Offset Against Collateral, Total	0	0
Derivative Liability, Fair Value, Gross Liability	1,088	2,144
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	1,088	2,144
Derivative, Collateral, Right to Reclaim Securities	0
Derivative, Collateral, Right to Reclaim Cash	1,088	2,144
Derivative, Net Liability Position, Aggregate Fair Value	0	0
Offsetting Liabilities, Gross	529,013	589,011
offsetting liabilities gross asset	0	0
Offsetting Liabilities, Total	529,013	589,011
Offsetting Liabilities, Securities Collateral	527,925	586,867
Offsetting Liabilities, Cash Collateral	1,088	2,144
Offsetting Liabilities, Net	$ 0	$ 0