Net Income (Loss) Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic and diluted:
Net loss	$ 12,201	$ (44,799)	$ (42,573)	$ (12,011)	$ (46,536)	$ (15,880)	$ (9,898)	$ (10,593)	$ (87,182)	$ (82,907)	$ (15,486)
Basic:
Weighted-average common shares outstanding, basic (in shares)									48,592	42,269	39,665
Dilutive effect of stock options, warrants, unvested awards									0	0	0
Diluted:
Weighted-average common shares outstanding, diluted (in shares)									48,592	42,269	39,665
Net loss per share :
Basic (in dollars per share)	$ 0.25	$ (0.91)	$ (0.86)	$ (0.26)	$ (1.09)	$ (0.38)	$ (0.23)	$ (0.25)	$ (1.79)	$ (1.96)	$ (0.39)
Diluted (in dollars per share)	$ 0.25	$ (0.91)	$ (0.86)	$ (0.26)	$ (1.09)	$ (0.38)	$ (0.23)	$ (0.25)	$ (1.79)	$ (1.96)	$ (0.39)