Unaudited Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive 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, net	(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, 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]
Net income	27,122
Foreign currency translation adjustments	(159)
Ending balance (in shares) at Sep. 30, 2018		58,419,742		20,220,227
Ending balance at Sep. 30, 2018	459,662	$ 1	447,933	$ (155,947)	169,301	(1,626)
Beginning balance (in shares) at Mar. 31, 2018		53,307,083		20,220,227
Beginning balance at Mar. 31, 2018	199,329	$ 1	202,344	$ (155,947)	155,105	(2,174)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		4,645,000
Issuance of common stock	233,993		233,993
Issuance of common stock under employee plans (in shares)		278,687
Issuance of common stock under employee plans, net	(6,800)		(6,800)
Stock-based compensation	4,954		4,954
Issuance of common stock for business combination (in shares)		58,843
Issuance of common stock for business combination	8,226		8,226
Net income	8,485				8,485
Foreign currency translation adjustments	655					655
Ending balance (in shares) at Jun. 30, 2018		58,289,613		20,220,227
Ending balance at Jun. 30, 2018	448,842	$ 1	442,717	$ (155,947)	163,590	(1,519)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		130,129
Issuance of common stock under employee plans, net	(1,039)		(1,039)
Stock-based compensation	6,255		6,255
Net income	5,711				5,711
Foreign currency translation adjustments	(107)					(107)
Ending balance (in shares) at Sep. 30, 2018		58,419,742		20,220,227
Ending balance at Sep. 30, 2018	459,662	$ 1	447,933	$ (155,947)	169,301	(1,626)
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, 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	480,539	$ 1	460,146	$ (155,947)	177,802	(1,463)
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]
Net income	13,261
Foreign currency translation adjustments	(285)
Ending balance (in shares) at Sep. 30, 2019		59,320,793		20,220,227
Ending balance at Sep. 30, 2019	507,647	$ 1	480,747	$ (155,947)	184,644	(1,798)
Beginning balance (in shares) at Mar. 31, 2019		59,109,286		20,220,227
Beginning balance at Mar. 31, 2019	480,539	$ 1	460,146	$ (155,947)	177,802	(1,463)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		71,832
Issuance of common stock under employee plans, net	(869)		(869)
Stock-based compensation	8,627		8,627
Issuance of common stock for business combination (in shares)		70,613
Issuance of common stock for business combination	0
Net income	738				738
Foreign currency translation adjustments	(108)					(108)
Ending balance (in shares) at Jun. 30, 2019		59,251,731		20,220,227
Ending balance at Jun. 30, 2019	488,927	$ 1	467,904	$ (155,947)	178,540	(1,571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee plans (in shares)		69,062
Issuance of common stock under employee plans, net	(1,134)		(1,134)
Stock-based compensation	13,977		13,977
Net income	6,104				6,104
Foreign currency translation adjustments	(227)					(227)
Ending balance (in shares) at Sep. 30, 2019		59,320,793		20,220,227
Ending balance at Sep. 30, 2019	$ 507,647	$ 1	$ 480,747	$ (155,947)	$ 184,644	$ (1,798)