Fair Value Measurements - Valuation Technique (Details)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Valuation technique for assets measured and recorded at fair value
Expected dividend yield (as a percent)	0.00%
Minimum
Valuation technique for assets measured and recorded at fair value
Risk-free interest rate (as a percent)	1.01%	0.73%
Volatility (as a percent)	62.00%	59.50%
Expected average term	7 months 21 days	1 year 7 months 21 days
Maximum
Valuation technique for assets measured and recorded at fair value
Risk-free interest rate (as a percent)	2.36%	0.86%
Volatility (as a percent)	108.77%	95.23%
Expected average term	10 years	2 years 6 months 18 days