Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 231,432	$ 17		$ 265,265	$ (30,202)	$ (3,648)
Beginning balance, shares at Dec. 31, 2015		16,723,994
Stock-based compensation	8,023			8,023
Exercise of stock options and issuance of restricted stock	4,303			4,303
Exercise of stock options and issuance of restricted stock, shares		279,841
Excess tax benefit of stock options exercised	4,070			4,070
Employee stock purchase plan	1,732			1,732
Employee stock purchase plan, shares		33,357
Stock issued for acquisition	2,922			2,922
Stock issued for acquisition, Shares		43,953
Net income	4,963				4,963
Foreign currency translation adjustments	336					336
Reclassification of gain (loss) on investments into earnings	18					18
Unrealized gain (loss) on investments, net of tax	(32)					(32)
Ending balance at Dec. 31, 2016	257,767	$ 17		286,315	(25,239)	(3,326)
Ending balance, shares at Dec. 31, 2016		17,081,145
Stock-based compensation	12,728			12,728
Exercise of stock options and issuance of restricted stock	1,410			1,410
Exercise of stock options and issuance of restricted stock, shares		135,906
Cumulative-effect adjustment for previously unrecognized excess tax benefits	16,277				16,277
Employee stock purchase plan	1,933			1,933
Employee stock purchase plan, shares		40,968
Retirement of escrow shares	(523)			(523)
Retirement of escrow shares, shares		(8,866)
Repurchases of common stock	(5,815)		$ (5,815)
Repurchases of common stock, shares		(122,147)	122,147
Net income	351				351
Foreign currency translation adjustments	3,944					3,944
Reclassification of gain (loss) on investments into earnings	39					39
Ending balance at Dec. 31, 2017	288,111	$ 17	$ (5,815)	301,863	(8,611)	657
Ending balance, shares at Dec. 31, 2017		17,127,006	122,147
Stock-based compensation	11,270			11,270
Exercise of stock options and issuance of restricted stock	14,344	$ 1		14,343
Exercise of stock options and issuance of restricted stock, shares		433,199
Employee stock purchase plan	1,745			1,745
Employee stock purchase plan, shares		34,798
Repurchases of common stock	(19,864)		$ (19,864)
Repurchases of common stock, shares		(289,745)	289,745
Stock issued for acquisition	3,371			3,371
Stock issued for acquisition, Shares		40,478
Net income	23,872				23,872
Foreign currency translation adjustments	(3,999)					(3,999)
Reclassification of gain (loss) on investments into earnings	(273)					(273)
Unrealized gain (loss) on investments, net of tax	397					397
Ending balance at Dec. 31, 2018	$ 318,974	$ 18	$ (25,679)	$ 332,592	$ 15,261	$ (3,218)
Ending balance, shares at Dec. 31, 2018		17,345,736	411,892