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, 2017		34,083,112
Beginning balance at Dec. 31, 2017	$ 790,244	$ 341	$ 1,271,628	$ (3,908)	$ (477,817)
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)		239,081
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings	(2,224)	$ 2	(2,226)
Non-cash equity based compensation	5,533		5,533
Unrealized losses on securities, net of tax	(454)			(454)
Net loss	(54,242)				(54,242)
Ending balance (in shares) at Mar. 31, 2018		34,322,193
Ending balance at Mar. 31, 2018	$ 739,995	$ 343	1,274,935	(4,362)	(530,921)
Beginning balance (in shares) at Dec. 31, 2018	34,606,760	34,606,760
Beginning balance at Dec. 31, 2018	$ 746,655	$ 346	1,292,736	(3,985)	(542,442)
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)		214,868
Net shares issued in connection with the exercise of stock options and vesting of restricted stock units, net of withholdings	(1,604)	$ 2	(1,606)
Repurchase of common stock pursuant to the 2016 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	4,873		4,873
Unrealized losses on securities, net of tax	609			609
Net loss	$ (122,084)				(122,084)
Ending balance (in shares) at Mar. 31, 2019	33,746,828	33,746,828
Ending balance at Mar. 31, 2019	$ 614,719	$ 337	$ 1,282,284	$ (3,376)	$ (664,526)