Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss	Total
Beginning balance (in shares) at Dec. 31, 2018	58,810,637		20,220,227
Beginning balance at Dec. 31, 2018	$ 1	$ 453,400	$ (155,947)	$ 171,383	$ (1,513)	$ 467,324
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans, net (in shares)	298,649
Issuance of common stock under employee plans, net		(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	$ 1	460,146	$ (155,947)	177,802	(1,463)	480,539
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of applying a change in accounting principle, net of tax				(640)		(640)
Beginning balance (in shares) at Dec. 31, 2019	59,497,759		20,220,227
Beginning balance at Dec. 31, 2019	$ 1	528,272	$ (155,947)	172,265	(1,096)	543,495
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans, net (in shares)	315,404
Issuance of common stock under employee plans, net		(5,162)				(5,162)
Stock-based compensation		20,195				20,195
Net income				4,074		4,074
Foreign currency translation adjustments					(2,372)	(2,372)
Ending balance (in shares) at Mar. 31, 2020	59,813,163		20,220,227
Ending balance at Mar. 31, 2020	$ 1	$ 543,305	$ (155,947)	$ 175,699	$ (3,468)	$ 559,590