Derivative Financial Instruments Offsetting of Derivative Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting Liabilities [Line Items]
Derivative Liability	$ 289	$ 1,383
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(90)	(1,322)
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 199	$ 61