Net Loss Per Common 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, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic and diluted net loss per common share calculation:
Net loss					$ (193,420)	$ (105,717)	$ (116,772)
Weighted average common shares outstanding (in shares)					35,486	34,580	33,258
Net loss per common share - basic and diluted (in dollars per share)	$ (1.86)	$ (1.71)	$ (0.85)	$ (1.03)	$ (5.45)	$ (3.06)	$ (3.51)
Anti-dilutive securities
Total (in shares)					4,080	3,297	3,731
Stock options outstanding
Anti-dilutive securities
Total (in shares)					3,359	3,009	3,680
Restricted stock units
Anti-dilutive securities
Total (in shares)					721	288	37
Warrants
Anti-dilutive securities
Total (in shares)					0	0	14