CONSOLIDATED STATEMENTS OF STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Series G Preferred Stock	Series H Preferred Stock	Common Stock	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2012	$ (65,558)			$ 45,488	$ (110,851)	$ (195)
Balance, shares at Dec. 31, 2012				10,709,224
Temporary Equity, Balance at Dec. 31, 2012		$ 59,059	$ 63,819
Temporary Equity, Balance, shares at Dec. 31, 2012		5,391,441	4,124,986
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,147				13,147
Other comprehensive loss	4					4
Issuance of common stock from vested restricted stock units, (in shares)				36,512
Issuance of common stock from exercise of stock options	7,109			$ 7,109
Issuance of common stock from exercise of stock options, (in shares)				5,730,544
Repurchase of common stock	$ (3,342)				(3,342)
Shares withheld for taxes and not issued	(809,012)			(809,012)
Adjustment related to withholding taxes	$ (8,643)				(8,643)
Repurchase of common stock, shares				(407,728)
Stock-based compensation expense	5,953			$ 5,953
Excess tax benefit from equity incentive plan activity	15,610			15,610
Special dividend	(357,520)				(357,520)
Balance at Dec. 31, 2013	(393,240)			$ 74,160	(467,209)	(191)
Balance, shares at Dec. 31, 2013				15,259,540
Temporary Equity, Balance at Dec. 31, 2013		$ 59,059	$ 63,819
Temporary Equity, Balance, shares at Dec. 31, 2013		5,391,441	4,124,986
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,497				15,497
Other comprehensive loss	(123)					(123)
Issuance of common stock from vested restricted stock units, (in shares)				4,250
Issuance of common stock for employee stock purchase plan	3,393			$ 3,393
Issuance of common stock for employee stock purchase plan (in shares)				249,494
Conversion of preferred stock	(122,878)	$ (59,059)	$ (63,819)	$ (122,878)
Conversion of preferred stock (in shares)		(5,391,441)	(4,124,986)	(38,065,708)
Issuance of common stock from exercise of stock options	2,193			$ 2,193
Issuance of common stock from exercise of stock options, (in shares)				1,712,278
Issuance of common stock, net of initial public offering costs	217,796			$ 217,796
Issuance of common stock, net of initial public offering costs (in shares)				15,091,074
Repurchase of common stock	$ (15,009)				(15,009)
Shares withheld for taxes and not issued	(80,599)			(80,599)
Adjustment related to withholding taxes	$ (1,431)				(1,431)
Repurchase of common stock, shares	(490,419)			(490,419)
Stock-based compensation expense	$ 10,660			$ 10,660
Excess tax benefit from equity incentive plan activity	9,663			9,663
Excess tax benefit from initial public offering	1,939			1,939
Special dividend forfeited	25				25
Balance at Dec. 31, 2014	(25,759)			$ 442,682	(468,127)	(314)
Balance, shares at Dec. 31, 2014				69,811,326
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,695				31,695
Other comprehensive loss	(407)					(407)
Issuance of common stock from vested restricted stock units, (in shares)				106,136
Issuance of common stock for employee stock purchase plan	$ 5,315			$ 5,315
Issuance of common stock for employee stock purchase plan (in shares)	272,836			272,836
Issuance of common stock from exercise of stock options	$ 7,166			$ 7,166
Issuance of common stock from exercise of stock options, (in shares)	2,112,131			2,112,131
Repurchase of common stock	$ (48,364)				(48,364)
Shares withheld for taxes and not issued	(35,379)			(35,379)
Adjustment related to withholding taxes	$ (799)				(799)
Repurchase of common stock, shares	(1,895,625)			(1,895,625)
Stock-based compensation expense	$ 17,742			$ 17,742
Excess tax benefit from equity incentive plan activity	20,670			20,670
Excess tax benefit from initial public offering	822			822
Balance at Dec. 31, 2015	$ 8,081			$ 494,397	$ (485,595)	$ (721)
Balance, shares at Dec. 31, 2015				70,371,425