CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	(Accumulated Deficit) Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Impact to Retained Earnings from adoption | ASU 2016-09				$ 440	$ (440)
Balance	$ 610,710	$ 407		624,069	(10,024)	$ (3,742)
Balance at Dec. 31, 2016	610,710	407		623,629	(9,584)	(3,742)
Net income	39,122				39,122
Foreign currency translation	3,008					3,008
Stock-based compensation expense	4,463			4,463
Stock options exercised	1,812	1		1,811
Repurchases of common stock	(149,551)	(51)			(149,500)
Treasury stock purchases	(6,032)	(2)	$ (6,030)
Tax effect of initial public offering related costs	(2)			(2)
Balance at Dec. 31, 2017	503,530	355	(6,030)	630,341	(120,402)	(734)
Impact to Retained Earnings from adoption | ASU 2014-09	5,730				5,730
Balance	509,260	355	(6,030)	630,341	(114,672)	(734)
Net income	73,185				73,185
Foreign currency translation	(1,783)					(1,783)
Stock-based compensation expense	6,499			6,499
Stock options exercised	2,542	1		2,541
Balance at Dec. 31, 2018	589,703	356	(6,030)	639,381	(41,487)	(2,517)
Impact to Retained Earnings from adoption | ASU 2016-02	9,153				9,153
Balance	598,856	356	(6,030)	639,381	(32,334)	(2,517)
Net income	100,443				100,443
Foreign currency translation	(224)					(224)
Stock-based compensation expense	20,741			20,741
Stock options exercised	6,467	4		6,463
Balance at Dec. 31, 2019	$ 726,283	$ 360	$ (6,030)	$ 666,585	$ 68,109	$ (2,741)