Trade Receivables - Allowance for Doubtful Accounts Rollforward (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
January 1	$ (16,068)	$ (25,918)
Allowance for credit losses through retained earnings	(21,040)	(6,042)
Reversal of provision	6,974	12,318
Currency translation adjustment	323	96
June 30	(33,294)	(19,546)
Retained Earnings
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses through retained earnings	$ (3,483)	$ 0