Trade Receivables - Allowance for Doubtful Accounts Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ (6,264)	$ (3,930)	$ (2,529)
Provision for doubtful accounts	(9,898)	(2,660)	(2,248)
Reversal of provision	4,464	0	910
Change in consolidation scope	(221)	(99)	(450)
Currency translation adjustment	321	425	387
Balance at end of period	$ (11,598)	$ (6,264)	$ (3,930)