Summary of Significant Accounting Policies - Stock-Based Compensation (Details)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Summary of Significant Accounting Policies
Expected term	4 years	4 years
Expected volatility (as a percent)	61.71%	75.45%
Risk free rate (as a percent)	1.22%	1.27%