Derivative Instruments Derivative Instruments (Balance Sheet Offsetting) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivative Asset, Amount Offset by Liabiilty	$ 0	$ 0
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	16,369	10,457
Derivative Assets	16,369	10,457
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	16,251	10,948
Derivative Liabilities	16,251	10,948
Derivative Subject to Master Netting Agreement [Member]
Derivative Asset, Fair Value, Gross Asset	15,700	10,209
Derivative Asset, Amount Offset by Liabiilty	0	0
Derivative Asset, Net Amount Presented in the Balance Sheet	15,700	10,209
Derivative Asset, Not Offset, Policy Election Deduction	(16)	(251)
derivatve asset, fair value of collateral	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	15,684	9,958
Derivative Liability, Fair Value, Gross Liability	16,052	10,454
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Net Amount Presented in the Balance Sheet	16,052	10,454
Derivative Liability, Not Offset, Policy Election Deduction	(16)	(251)
Derivative Liability, Fair Value of Collateral	(14,456)	(8,738)
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,580	1,465
Derivative Not Subject to Master Netting Agreement [Member]
Derivative Asset, Fair Value, Gross Asset	669	248
Derivative Asset, Amount Offset by Liabiilty	0	0
Derivative Asset, Not Subject to Master Netting Arrangement	669	248
Derivative Liability, Fair Value, Gross Liability	199	494
Derivative Liability, Amount Offset by Asset	0	0
Derivative, Fair Value, Net	$ 199	$ 494