Weighted Average Shares Outstanding and Net (Loss) Income Per Share - Summary of Reconciliation of Weighted Average Shares Outstanding in Basic and Diluted Net (Loss) Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net (loss) income allocated to common shareholders for basic calculation	$ (8,385)	$ 14,133	$ (19,808)	$ (9,657)
Effect of dilutive convertible notes	$ 0	$ 0	$ 0	$ 0
Weighted average common shares outstanding, basic	41,044	39,827	40,074	39,738
Dilutive effect of convertible notes, restricted stock units and common stock options	0	566	0	0
Weighted average common shares outstanding, diluted	41,044	40,393	40,074	39,738
Net (loss) income per share, basic	$ (0.20)	$ 0.35	$ (0.49)	$ (0.24)
Net (loss) income per share, diluted	$ (0.20)	$ 0.35	$ (0.49)	$ (0.24)