Income Taxes Income Tax Contingency (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Abstract]
Unrecognized Tax Benefits, Increases Resulting from Current Period Tax Positions	$ 3,472	$ 983	$ 1,044
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	(180)	(83)	(640)
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(1,154)	(1,657)	(1,371)
Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations	(931)	(816)	(816)
Unrecognized Tax Benefits	$ 10,124	$ 8,557	$ 9,964	$ 11,747