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, 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)
Beginning Balance at Dec. 31, 2020	1,041,528	363	65,613	1,125,263	(149,711)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustment	(5,592)				(5,592)
Net income (loss)	(64,568)			(64,568)
Comprehensive income (loss)	(70,160)
Repurchase of common stock	(1,132)			(1,132)
Stock option expense	9,541		9,541
Ending Balance at Sep. 30, 2021	979,777	363	75,154	1,059,563	(155,303)
Beginning Balance at Jun. 30, 2021	995,324	363	71,878	1,071,838	(148,755)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustment	(6,548)				(6,548)
Net income (loss)	(11,143)			(11,143)
Comprehensive income (loss)	(17,691)
Repurchase of common stock	(1,132)			(1,132)
Stock option expense	3,276		3,276
Ending Balance at Sep. 30, 2021	$ 979,777	$ 363	$ 75,154	$ 1,059,563	$ (155,303)