Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		52,969,869		20,220,227
Beginning balance at Dec. 31, 2017	$ 167,444	$ 1	$ 201,672	$ (155,947)	$ 123,185	$ (1,467)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		337,214
Issuance of common stock under employee plans	(3,421)		(3,421)
Stock-based compensation	4,093		4,093
Net income	12,926				12,926
Foreign currency translation adjustments	(707)					(707)
Ending balance (in shares) at Mar. 31, 2018		53,307,083		20,220,227
Ending balance at Mar. 31, 2018	199,329	$ 1	202,344	$ (155,947)	155,105	(2,174)
Beginning balance (in shares) at Dec. 31, 2018		58,810,637		20,220,227
Beginning balance at Dec. 31, 2018	467,324	$ 1	453,400	$ (155,947)	171,383	(1,513)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		298,649
Issuance of common stock under employee plans	(1,159)		(1,159)
Stock-based compensation	7,905		7,905
Net income	6,419				6,419
Foreign currency translation adjustments	50					50
Ending balance (in shares) at Mar. 31, 2019		59,109,286		20,220,227
Ending balance at Mar. 31, 2019	$ 480,539	$ 1	$ 460,146	$ (155,947)	$ 177,802	$ (1,463)