Goodwill - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Impairment charge		$ 0
Foreign exchange impact		(2,754)	$ (3,557)
Goodwill impairment	$ 37,500	$ 0	$ 0	$ 37,539