CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQIUTY (DEFICIT) - USD ($)	Total	Series G and H Preferred Stock	Common Stock	Common Stock Including Additional Paid in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2013	$ (393,240,000)	$ 122,878,000		$ 74,160,000	$ (467,209,000)	$ (191,000)
Balance, shares at Dec. 31, 2013		9,516,427	15,259,540
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,497,000				15,497,000
Other comprehensive income (loss)	(123,000)					(123,000)
Issuance of common stock from vested restricted stock units, (in shares)			4,250
Issuance of common stock for employee stock purchase plan	$ 3,393,000			3,393,000
Issuance of common stock for employee stock purchase plan (in shares)	249,494		249,494
Conversion of preferred stock	$ 122,878,000	$ (122,878,000)		122,878,000
Conversion of preferred stock (in shares)		(9,516,427)	38,065,708
Issuance of common stock from exercise of stock options	2,193,000			2,193,000
Issuance of common stock from exercise of stock options, (in shares)			1,712,278
Issuance of common stock, net of initial public offering costs	217,796,000			217,796,000
Issuance of common stock, net of initial public offering costs (in shares)			15,091,074
Stock-based compensation expense	10,660,000			10,660,000
Repurchase of common stock	$ (15,009,000)				(15,009,000)
Repurchase of common stock, shares	(490,419)		(490,419)
Awards effectively repurchased for required employee withholding taxes	$ (1,431,000)				(1,431,000)
Awards effectively repurchased for required employee withholding taxes (in shares)			(80,599)
Excess tax benefits from equity incentive plan activity	9,663,000			9,663,000
Realized tax benefit of deductible IPO transaction costs	1,939,000			1,939,000
Special dividend	25,000				25,000
Balance at Dec. 31, 2014	(25,759,000)	$ 0		442,682,000	(468,127,000)	(314,000)
Balance, shares at Dec. 31, 2014		0	69,811,326
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,695,000				31,695,000
Other comprehensive income (loss)	(407,000)					(407,000)
Issuance of common stock from vested restricted stock units, (in shares)			106,136
Issuance of common stock for employee stock purchase plan	$ 5,315,000			5,315,000
Issuance of common stock for employee stock purchase plan (in shares)	272,836		272,836
Issuance of common stock from exercise of stock options	$ 7,166,000			7,166,000
Issuance of common stock from exercise of stock options, (in shares)			2,112,131
Stock-based compensation expense	17,742,000			17,742,000
Repurchase of common stock	$ (48,364,000)				(48,364,000)
Repurchase of common stock, shares	(1,895,625)		(1,895,625)
Awards effectively repurchased for required employee withholding taxes	$ (799,000)				(799,000)
Awards effectively repurchased for required employee withholding taxes (in shares)			(35,379)
Excess tax benefits from equity incentive plan activity	20,670,000			20,670,000
Realized tax benefit of deductible IPO transaction costs	822,000			822,000
Balance at Dec. 31, 2015	8,081,000			494,397,000	(485,595,000)	(721,000)
Balance, shares at Dec. 31, 2015			70,371,425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	61,406,000				61,406,000
Other comprehensive income (loss)	117,000					117,000
Issuance of common stock from vested restricted stock units, (in shares)			695,253
Issuance of common stock for employee stock purchase plan	$ 4,506,000			4,506,000
Issuance of common stock for employee stock purchase plan (in shares)	283,644		283,644
Issuance of common stock from exercise of stock options	$ 5,272,000			5,272,000
Issuance of common stock from exercise of stock options, (in shares)	1,297,812		1,297,812
Stock-based compensation expense	$ 26,318,000			26,318,000
Repurchase of common stock	$ (71,604,000)				(71,604,000)
Repurchase of common stock, shares	(3,414,675)		(3,414,675)
Awards effectively repurchased for required employee withholding taxes	$ (4,145,000)				(4,145,000)
Awards effectively repurchased for required employee withholding taxes (in shares)			(217,769)
Excess tax benefits from equity incentive plan activity	4,639,000			4,639,000
Balance at Dec. 31, 2016	$ 34,590,000			$ 535,132,000	$ (499,938,000)	$ (604,000)
Balance, shares at Dec. 31, 2016			69,015,690