Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total		Common Stock	Retained Earnings		Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2015	$ 126,991		$ 796	$ 127,522		$ (1,327)
Balance, shares at Dec. 31, 2015			31,005
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,178	[1],[2]		34,178	[3]
Unrealized loss on marketable securities, net of income tax expense	8	[4]				8
Gain (loss) on derivative securities, effective portion, net of income tax (benefit) expense	(24)	[4]				(24)
Foreign currency translation adjustment, including income tax expense (benefit)	126	[4]				126
Stock-based compensation expense	2,613		$ 2,613
Common stock issued under equity compensation plan, net of shares withheld for tax payments, in shares			116
Common stock issued under equity compensation plan, net of shares withheld for tax payments	117		$ 117
Common stock issued under employee stock purchase plan, shares			24
Common stock issued under employee stock purchase plan	381		$ 381
Tax benefit related to stock-based awards	1,857		$ 1,857
Repurchased shares, in shares			(320)
Repurchased shares	(5,390)		$ (5,186)	(204)
Balance, shares at Dec. 31, 2016			30,825
Ending balance at Dec. 31, 2016	160,857		$ 578	161,496		(1,217)
Beginning balance at Dec. 31, 2015	126,991		$ 796	127,522		(1,327)
Balance, shares at Dec. 31, 2015			31,005
Balance, shares at Dec. 31, 2018			29,545
Ending balance at Dec. 31, 2018	182,596		$ 215	183,290		(909)
Beginning balance at Dec. 31, 2016	160,857		$ 578	161,496		(1,217)
Balance, shares at Dec. 31, 2016			30,825
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26,267	[1],[2]		26,267	[3]
Unrealized loss on marketable securities, net of income tax expense	(56)	[4]				(56)
Gain (loss) on derivative securities, effective portion, net of income tax (benefit) expense	240	[4]				240
Foreign currency translation adjustment, including income tax expense (benefit)	774	[4]				774
Stock-based compensation expense	1,856		$ 1,884	(28)
Common stock issued under equity compensation plan, net of shares withheld for tax payments, in shares			231
Common stock issued under equity compensation plan, net of shares withheld for tax payments	(181)		$ (181)
Common stock issued under employee stock purchase plan, shares			37
Common stock issued under employee stock purchase plan	487		$ 487
Repurchased shares, in shares			(788)
Repurchased shares	(11,055)		$ (2,768)	(8,287)
Balance, shares at Dec. 31, 2017			30,305
Ending balance at Dec. 31, 2017	179,189	[5]	$ 0	179,448		(259)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,658			14,658
Unrealized loss on marketable securities, net of income tax expense	58					58
Gain (loss) on derivative securities, effective portion, net of income tax (benefit) expense	7
Foreign currency translation adjustment, including income tax expense (benefit)	(715)					(715)
Stock-based compensation expense	1,981		$ 1,981	0
Common stock issued under equity compensation plan, net of shares withheld for tax payments, in shares			192
Common stock issued under equity compensation plan, net of shares withheld for tax payments	(30)		$ (30)
Common stock issued under employee stock purchase plan, shares			38
Common stock issued under employee stock purchase plan	444		$ 444
Repurchased shares, in shares			(990)
Repurchased shares	(12,996)		$ (2,180)	(10,816)
Balance, shares at Dec. 31, 2018			29,545
Ending balance at Dec. 31, 2018	$ 182,596		$ 215	$ 183,290		$ (909)

[1] See Note 4.

[2] See Note 4.

[3] See Note 4.

[4] See Note 4.

[5] See Note 4.