Derivative Instruments Derivative Instruments (Balance Sheet Offsetting) (Details) - USD ($) $ in Thousands	Jun. 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	10,621	10,457
Derivative Assets	10,621	10,457
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	10,348	10,948
Derivative Liabilities	10,348	10,948
Derivative Subject to Master Netting Agreement [Member]
Derivative Asset, Fair Value, Gross Asset	10,145	10,209
Derivative Asset, Amount Offset by Liabiilty	0	0
Derivative Asset, Net Amount Presented in the Balance Sheet	10,145	10,209
Derivative Asset, Not Offset, Policy Election Deduction	(45)	(251)
derivatve asset, fair value of collateral	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	10,100	9,958
Derivative Liability, Fair Value, Gross Liability	10,294	10,454
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Net Amount Presented in the Balance Sheet	10,294	10,454
Derivative Liability, Not Offset, Policy Election Deduction	(45)	(251)
Derivative Liability, Fair Value of Collateral	(7,580)	(8,738)
Derivative Liability, Fair Value, Amount Offset Against Collateral	2,669	1,465
Derivative Not Subject to Master Netting Agreement [Member]
Derivative Asset, Fair Value, Gross Asset	476	248
Derivative Asset, Amount Offset by Liabiilty	0	0
Derivative Asset, Not Subject to Master Netting Arrangement	476	248
Derivative Liability, Fair Value, Gross Liability	54	494
Derivative Liability, Amount Offset by Asset	0	0
Derivative, Fair Value, Net	$ 54	$ 494