CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		34,606,760
Beginning balance at Dec. 31, 2018	$ 741,557	$ 346	$ 1,292,736	$ (3,985)	$ (547,540)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings (in shares)		278,474
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings	(1,787)	$ 3	(1,790)
Issuance of common stock under employee stock purchase plan (in shares)		105,075
Issuance of common stock under employee stock purchase plan	851	$ 1	850
Repurchase of common stock pursuant to the share repurchase program (in shares)		(1,074,800)
Repurchase of common stock pursuant to the share repurchase program	(13,730)	$ (11)	(13,719)
Non-cash equity based compensation	14,381		14,381
Unrealized (losses) gains on securities, net of tax	786			786
Net income (loss)	(267,509)				(267,509)
Ending balance (in shares) at Sep. 30, 2019		33,915,509
Ending balance at Sep. 30, 2019	474,549	$ 339	1,292,458	(3,199)	(815,049)
Beginning balance (in shares) at Jun. 30, 2019		33,899,954
Beginning balance at Jun. 30, 2019	493,751	$ 339	1,287,553	(3,032)	(791,109)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings (in shares)		15,555
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings	(69)		(69)
Non-cash equity based compensation	4,974		4,974
Unrealized (losses) gains on securities, net of tax	(167)			(167)
Net income (loss)	(23,940)				(23,940)
Ending balance (in shares) at Sep. 30, 2019		33,915,509
Ending balance at Sep. 30, 2019	$ 474,549	$ 339	1,292,458	(3,199)	(815,049)
Beginning balance (in shares) at Dec. 31, 2019	33,999,081	33,999,081
Beginning balance at Dec. 31, 2019	$ 279,816	$ 339	1,297,917	(3,239)	(1,015,201)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings (in shares)		408,152
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings	(1,232)	$ 5	(1,237)
Issuance of common stock under employee stock purchase plan (in shares)		96,202
Issuance of common stock under employee stock purchase plan	631	$ 1	630
Non-cash equity based compensation	8,102		8,102
Unrealized (losses) gains on securities, net of tax	171			171
Net income (loss)	$ (31,466)				(31,466)
Ending balance (in shares) at Sep. 30, 2020	34,503,435	34,503,435
Ending balance at Sep. 30, 2020	$ 256,022	$ 345	1,305,412	(3,068)	(1,046,667)
Beginning balance (in shares) at Jun. 30, 2020		34,463,373
Beginning balance at Jun. 30, 2020	244,106	$ 344	1,303,095	(2,964)	(1,056,369)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings (in shares)		40,062
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings	95	$ 1	94
Non-cash equity based compensation	2,223		2,223
Unrealized (losses) gains on securities, net of tax	(104)			(104)
Net income (loss)	$ 9,702				9,702
Ending balance (in shares) at Sep. 30, 2020	34,503,435	34,503,435
Ending balance at Sep. 30, 2020	$ 256,022	$ 345	$ 1,305,412	$ (3,068)	$ (1,046,667)