Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2015		53,692,192		18,432,158
Beginning balance at Dec. 31, 2015	$ 157,004	$ 1	$ 178,143	$ (122,201)	$ 83	$ 100,978
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		421,128
Issuance of common stock under employee plans	(1,294)		(1,294)
Stock-based compensation	9,369		9,369
Excess tax benefit from stock-based compensation	1,438		1,438
Purchase of treasury stock (in shares)		(1,788,069)		(1,788,069)
Purchase of treasury stock	(33,746)			$ (33,746)
Net income	17,297					17,297
Foreign currency translation adjustments	820				820
Ending balance (in shares) at Dec. 31, 2016		52,325,251		20,220,227
Ending balance at Dec. 31, 2016	150,888	$ 1	187,656	$ (155,947)	903	118,275
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		644,618
Issuance of common stock under employee plans	(2,069)		(2,069)
Stock-based compensation	15,610		15,610
Net income	5,207					5,207
Foreign currency translation adjustments	(2,370)				(2,370)
Ending balance (in shares) at Dec. 31, 2017		52,969,869		20,220,227
Ending balance at Dec. 31, 2017	167,444	$ 1	201,672	$ (155,947)	(1,467)	123,185
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of applying a change in accounting principle	178		475			(297)
Issuance of common stock (in shares)		4,645,000
Issuance of common stock	233,993		233,993
Issuance of common stock for business combination (in shares)		58,843
Issuance of common stock for business combination	8,226		8,226
Issuance of common stock under employee plans (in shares)		1,136,925
Issuance of common stock under employee plans	(12,370)		(12,370)
Stock-based compensation	21,879		21,879
Net income	29,205					29,205
Foreign currency translation adjustments	(46)				(46)
Ending balance (in shares) at Dec. 31, 2018		58,810,637		20,220,227
Ending balance at Dec. 31, 2018	467,324	$ 1	$ 453,400	$ (155,947)	$ (1,513)	171,383
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of applying a change in accounting principle	$ 18,993					$ 18,993