Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Treasury stock at cost	Accumulated other comprehensive loss	Retained earnings (accumulated deficit)
Balance (in shares) at Dec. 31, 2015		35,936,000
Balance at Dec. 31, 2015	$ 336,969	$ 36	$ 343,166	$ (5,003)	$ 0	$ (1,230)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		926,000
Exercise of stock options	16,070	$ 1	16,069
Issuance of common stock under Employee Stock Purchase Plan (in shares)		53,000
Issuance of common stock under Employee Stock Purchase Plan	2,194		2,194
Issuance of restricted stock units, net of shares withheld for employee taxes (in shares)		213,000
Issuance of restricted stock units, net of shares withheld for employee taxes	(6,108)		(6,108)
Tax benefit from the exercise of stock options	14,806		14,806
Treasury stock acquired (in shares)		(226,000)
Treasury stock acquired	(9,371)			(9,371)
Stock-based compensation	27,180		27,180
Other comprehensive loss, net of tax	0
Net income	15,902					15,902
Balance (in shares) at Dec. 31, 2016		36,902,000
Balance at Dec. 31, 2016	397,642	$ 37	397,307	(14,374)	0	14,672
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		810,000
Exercise of stock options	$ 14,269	$ 2	14,267
Public stock offering, net of issuance costs (in shares)	1,955,000
Public stock offering, net of issuance costs	$ 130,789	$ 2	130,787
Issuance of common stock under Employee Stock Purchase Plan (in shares)	48,443	48,000
Issuance of common stock under Employee Stock Purchase Plan	$ 2,681		2,681
Issuance of restricted stock units, net of shares withheld for employee taxes (in shares)		191,000
Issuance of restricted stock units, net of shares withheld for employee taxes	$ (9,019)		(9,019)
Treasury stock acquired (in shares)	(134,900)	(135,000)
Treasury stock acquired	$ (7,935)			(7,935)
Stock-based compensation	25,649		25,649
Capitalized stock-based compensation	459		459
Other comprehensive loss, net of tax	(354)				(354)
Net income	54,387					54,387
Balance (in shares) at Dec. 31, 2017		39,771,000
Balance at Dec. 31, 2017	$ 612,250	$ 41	562,131	(22,309)	(354)	72,741
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	54,000	54,000
Exercise of stock options	$ 1,395		1,395
Issuance of common stock under Employee Stock Purchase Plan (in shares)	18,037	18,000
Issuance of common stock under Employee Stock Purchase Plan	$ 869		869
Issuance of restricted stock units, net of shares withheld for employee taxes (in shares)		10,000
Issuance of restricted stock units, net of shares withheld for employee taxes	$ (281)		(281)
Treasury stock acquired (in shares)	0
Stock-based compensation	$ 18,088		18,088
Capitalized stock-based compensation	319		319
Other comprehensive loss, net of tax	(400)				(400)
Net income	25,970
Balance (in shares) at Dec. 31, 2018		39,853,000
Balance at Dec. 31, 2018	$ 665,141	$ 41	$ 582,521	$ (22,309)	$ (754)	$ 105,642