Net Income (Loss) Per Share - Reconciliation of Basic and Diluted Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net (loss) income	$ (12,236)	$ 25,910
Weighted average shares:
Basic shares (in shares)	38,559	41,374
Effect of dilutive securities—options and warrants outstanding (in shares)	0	1,436
Diluted shares (in shares)	38,559	42,810
Net income (loss) per share - basic (in dollars per share)	$ (0.32)	$ 0.63
Net income (loss) per share - diluted (in dollars per share)	$ (0.32)	$ 0.61