Goodwill and Intangible Assets Goodwill Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill Rollforward [Abstract]
Goodwill	$ 33,872	$ 31,343	$ 36,747
Goodwill, Foreign Currency Translation Gain (Loss)	$ 2,529	$ (5,404)