Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 33,133	$ 35,087	$ 30,544
Charged to Expenses	8,022	9,192	12,005
Deductions	(8,751)	(9,907)	(5,353)
Translation Adjustments	777	(1,239)	(2,109)
Balance at End of Period	33,181	33,133	35,087
Deferred tax valuation allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	18,907	26,329	29,561
Charged to Expenses	1,411	2,160	6,283
Deductions	(1,275)	(9,517)	(8,068)
Translation Adjustments	1,135	(65)	(1,447)
Balance at End of Period	$ 20,178	$ 18,907	$ 26,329