CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Losses
Beginning Balance at Dec. 31, 2018	$ 1,096,162	$ 376	$ 34,953	$ 1,205,946	$ (145,113)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustment	(10,311)				(10,311)
Net income (loss)	(5,679)			(5,679)
Comprehensive income (loss)	(15,990)
Repurchase of common stock	(5,365)	(1)		(5,364)
Options exercised and awards vested	2,182	1	2,181
Stock option expense	15,746		15,746
Other	(63)		16	(79)
Ending Balance at Sep. 30, 2019	1,092,672	376	52,896	1,194,824	(155,424)
Beginning Balance at Jun. 30, 2019	1,097,128	376	43,053	1,199,502	(145,803)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustment	(9,621)				(9,621)
Net income (loss)	(1,310)			(1,310)
Comprehensive income (loss)	(10,931)
Repurchase of common stock	(3,368)	(1)		(3,367)
Options exercised and awards vested	2,182	1	2,181
Stock option expense	7,663		7,663
Other	(2)		(1)	(1)
Ending Balance at Sep. 30, 2019	1,092,672	376	52,896	1,194,824	(155,424)
Beginning Balance at Dec. 31, 2019	1,090,701	371	52,870	1,181,023	(143,563)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustment	(18,086)				(18,086)
Net income (loss)	(19,514)			(19,514)
Comprehensive income (loss)	(37,600)
Repurchase of common stock	(25,000)	(8)		(24,992)
Stock option expense	9,461		9,461
Ending Balance at Sep. 30, 2020	1,037,562	363	62,331	1,136,517	(161,649)
Beginning Balance at Jun. 30, 2020	1,015,387	363	59,327	1,122,191	(166,494)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustment	4,845				4,845
Net income (loss)	14,326			14,326
Comprehensive income (loss)	19,171
Stock option expense	3,004		3,004
Ending Balance at Sep. 30, 2020	$ 1,037,562	$ 363	$ 62,331	$ 1,136,517	$ (161,649)