CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	AOCI Attributable to Parent
Balance at Dec. 31, 2014	$ 401,970	$ 313		$ 417,553	$ (14,336)	$ (1,560)
Net income (loss)	(8,673)				(8,673)
Issuance of common stock	608	1		607
Foreign currency translation adjustments, net of taxes	(999)					(999)
Stock-based compensation expense	21,127	12		21,115
Stock options exercised	250			250
Tax benefit deficiency from stock-based compensation	(809)			(809)
Balance at Dec. 31, 2015	413,474	326		438,716	(23,009)	(2,559)
Net income (loss)	13,425				13,425
Issuance of common stock	173,578	80		173,498
Foreign currency translation adjustments, net of taxes	(1,183)					(1,183)
Stock-based compensation expense	2,777	1		2,776
Stock options exercised	678			678
Common stock issuance costs	(2,719)			(2,719)
Reclassification of liability classified stock options upon IPO	10,463			10,463
Tax effect of initial public offering related costs	192			192
Tax benefit from stock-based compensation	25			25
Balance at Dec. 31, 2016	610,710	407		623,629	(9,584)	(3,742)
Impact to Retained Earnings from adoption of ASU 2016-09				440	(440)
BALANCE — January 1, 2017	610,710	407		624,069	(10,024)	(3,742)
Net income (loss)	39,122				39,122
Foreign currency translation adjustments, net of taxes	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)