CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, deferred income taxes	$ 1,747	$ (16,992)	$ 3,598	$ (27,680)
Net loss on cash flow hedging instruments, deferred income taxes	21	(813)	888	(398)
Pension liability adjustments, deferred income taxes	(523)	254	(1,567)	(1,002)
Unrealized gain (loss) on marketable securities, deferred income taxes	$ (3)	$ (9)	$ (6)	$ (7)