CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, deferred income taxes	$ 1,458	$ (4,977)	$ 1,851	$ (8,554)
Net loss on cash flow hedging instruments, deferred income taxes	611	401	867	415
Pension liability adjustments, deferred income taxes	(522)	(571)	(1,044)	(1,256)
Unrealized gain (loss) on marketable securities, deferred income taxes	$ 0	$ (2)	$ (3)	$ 2