Derivative Instruments Derivative Instruments (Balance Sheet Offsetting) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Derivative Asset, Amount Offset by Liabiilty	$ 0	$ 0
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	32,056	12,771
Derivative Assets	32,056	12,771
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	31,772	12,729
Derivative Liabilities	31,772	12,729
Derivative Subject to Master Netting Agreement [Member]
Derivative Asset, Fair Value, Gross Asset	31,174	12,071
Derivative Asset, Amount Offset by Liabiilty	0	0
Derivative Asset, Net Amount Presented in the Balance Sheet	31,174	12,071
Derivative Asset, Not Offset, Policy Election Deduction	(38)	(94)
derivatve asset, fair value of collateral	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	31,136	11,977
Derivative Liability, Fair Value, Gross Liability	31,762	12,299
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Net Amount Presented in the Balance Sheet	31,762	12,299
Derivative Liability, Not Offset, Policy Election Deduction	(38)	(94)
Derivative Liability, Fair Value of Collateral	(30,319)	(10,927)
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,405	1,278
Derivative Not Subject to Master Netting Agreement [Member]
Derivative Asset, Fair Value, Gross Asset	882	700
Derivative Asset, Amount Offset by Liabiilty	0	0
Derivative Asset, Not Subject to Master Netting Arrangement	882	700
Derivative Liability, Fair Value, Gross Liability	10	430
Derivative Liability, Amount Offset by Asset	0	0
Derivative Liability, Not Subject to Master Netting Arrangement	$ 10	$ 430