Consolidated statements of stockholders' equity - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid in Capital	Treasury Stock	Accumulated Deficit
Stockholders' equity, balance at beginning of the period at Dec. 31, 2017	$ 842,766	$ 468	$ 961,200		$ (118,902)
Balance at beginning of period (in shares) at Dec. 31, 2017		46,827,762
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	11,029		11,029
Stock-based compensation (in shares)		55,000
Restricted stock forfeited	(1)	$ (1)
Restricted stock forfeited (in shares)		(165,453)
Repurchase of common stock	$ (4,872)			$ (4,872)
Repurchase of common stock (in shares)	(256,895)	(256,895)
Net loss	$ (45,503)				(45,503)
Stockholders' equity, balance at end of the period at Sep. 30, 2018	$ 803,419	$ 467	$ 972,229	$ (4,872)	$ (164,405)
Balance at end of period (in shares) at Sep. 30, 2018		46,460,414