Employee Benefit Plans - Assumptions For Estimating Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jul. 23, 2014	May 12, 2011
Employee Benefit Plans
Compensation cost	$ 9.0	$ 7.5	$ 3.6
Stock options granted	3,702,500	3,960,000	4,245,000
Minimum
Assumptions for estimating fair value
Risk free rate (as a percent):	1.27%	1.52%	1.77%
Volatility (as a percent):	103.87%	104.03%	107.17%
Maximum
Assumptions for estimating fair value
Risk free rate (as a percent):	1.69%	1.87%	1.94%
Volatility (as a percent):	104.88%	105.29%	113.92%
Stock options
Employee Benefit Plans
Number of options outstanding (in shares)	14,760,054	11,700,786
Compensation cost	$ 9.0	$ 7.5	$ 3.4
Stock options granted	3,702,500	3,960,000	4,246,000
Assumptions for estimating fair value
Expected term of options (years)	6 years	6 years	6 years
the 2011 Plan | Stock options
Employee Benefit Plans
Maximum number of common stock shares available for issuance				17,000,000	1,000,000
Aggregate number of options granted (in shares)	14,800,000
Number of options outstanding (in shares)	14,800,000
Number of options available for issuance (in shares)	1,000,000
Expiration period	10 years
the 2011 Plan | Stock options | Minimum
Employee Benefit Plans
Vesting period	1 year
the 2011 Plan | Stock options | Maximum
Employee Benefit Plans
Vesting period	3 years
the 2011 Plan | Employees | Stock options
Employee Benefit Plans
Vesting period	3 years
Expiration period	10 years
the 2011 Plan | Board of Directors | Stock options
Employee Benefit Plans
Vesting period	1 year