Employee Benefit Plans - Assumptions For Estimating Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 23, 2014	Jul. 22, 2014	May. 16, 2012	May. 15, 2012	May. 12, 2011
Employee Benefit Plans
Compensation cost	$ 7.5	$ 3.6	$ 1.8
Stock options
Employee Benefit Plans
Number of options outstanding (in shares)	11,700,786	8,367,271
Compensation cost	$ 7.5	$ 3.4	$ 1.4
Stock options granted	3,960,000	4,246,000	3,090,900
Assumptions for estimating fair value
Expected term of options (years)	6 years	6 years	6 years
Risk Free interest rate, minimum	1.52%	1.77%	0.93%
Risk Free interest rate, maximum	1.87%	1.94%	1.70%
Volatility, minimum (as a percent):	104.03%	107.17%	92.46%
Volatility, maximum (as a percent):	105.29%	113.92%	107.01%
the 2011 Plan | Stock options
Employee Benefit Plans
Maximum number of common stock shares available for issuance				17,000,000	6,500,000	6,500,000	1,000,000	1,000,000
Aggregate number of options granted (in shares)	11,700,000
Number of options outstanding (in shares)	11,700,000
Number of options available for issuance (in shares)	4,300,000
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