Fair Value Measurements - Valuation Technique (Details)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Minimum
Valuation technique for assets measured and recorded at fair value
Risk-free interest rate (as a percent)	0.73%	0.28%
Volatility (as a percent)	59.50%	52.92%
Expected average term	1 year 7 months 21 days	11 months 1 day
Maximum
Valuation technique for assets measured and recorded at fair value
Risk-free interest rate (as a percent)	0.86%	1.375%
Volatility (as a percent)	95.23%	134.40%
Expected average term	2 years 6 months 18 days	3 years 6 months 18 days