Consolidated Statements of Changes in Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2016		36,756
Beginning balance at Dec. 31, 2016	$ (106,516)	$ 367	$ 226,462	$ (332,398)	$ (947)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	123,385			123,385
Other comprehensive income (loss)	(87)				(87)
Stock option exercises and employee stock plan purchases (in shares)		478
Stock option exercises and employee stock plan purchases	3,434	$ 5	3,429
Vesting of restricted stock awards and units (in shares)		744
Vesting of restricted stock awards and units	0	$ 8	(8)
Shares withheld to cover taxes (in shares)		(214)
Shares withheld to cover taxes	(2,853)	$ (2)	(2,851)
Stock-based compensation	5,928		5,928
Ending balance (in shares) at Dec. 31, 2017		37,765
Ending balance at Dec. 31, 2017	23,291	$ 378	232,960	(209,013)	(1,034)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,518			40,518
Forfeiture of dividend equivalent right	355			355
Other comprehensive income (loss)	(74)				(74)
Stock option exercises and employee stock plan purchases (in shares)		223
Stock option exercises and employee stock plan purchases	1,580	$ 2	1,578
Vesting of restricted stock awards and units (in shares)		672
Vesting of restricted stock awards and units	0	$ 7	(7)
Shares withheld to cover taxes (in shares)		(194)
Shares withheld to cover taxes	(3,386)	$ (2)	(3,384)
Stock-based compensation	8,718		8,718
Ending balance (in shares) at Dec. 31, 2018		38,466
Ending balance at Dec. 31, 2018	71,002	$ 385	239,865	(168,140)	(1,108)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,667			31,667
Other comprehensive income (loss)	148				148
Stock option exercises and employee stock plan purchases (in shares)		95
Stock option exercises and employee stock plan purchases	1,746	$ 1	1,745
Vesting of restricted stock awards and units (in shares)		796
Vesting of restricted stock awards and units	0	$ 8	(8)
Shares withheld to cover taxes (in shares)		(106)
Shares withheld to cover taxes	(2,454)	$ (1)	(2,453)
Stock-based compensation	12,492		12,492
Ending balance (in shares) at Dec. 31, 2019		39,251
Ending balance at Dec. 31, 2019	$ 114,601	$ 393	$ 251,641	$ (136,473)	$ (960)