Offsetting Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Offsetting Assets and Liabilities [Abstract]
Derivative Asset, Fair Value, Gross Asset	$ 1,020	$ 2,148
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	1,020	2,148
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Securities Sold Under Agreements to Repurchase, Gross	534,669	586,867
Securities Sold under Agreements to Repurchase, Asset	0	0
Securities Sold Under Agreements to Repurchase, Total	534,669	586,867
Securities Sold Under Agreements to Repurchase, Collateral, Right to Reclaim Securities	534,669	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	1,028	2,144
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	1,028	2,144
Derivative, Collateral, Right to Reclaim Securities	0
Derivative, Collateral, Right to Reclaim Cash	1,028	2,144
Derivative, Net Liability Position, Aggregate Fair Value	0	0
Offsetting Liabilities, Gross	535,697	589,011
Offsetting Liabilities, Gross Asset	0	0
Offsetting Liabilities, Total	535,697	589,011
Offsetting Liabilities, Securities Collateral	534,669	586,867
Offsetting Liabilities, Cash Collateral	1,028	2,144
Offsetting Liabilities, Net	$ 0	$ 0