Summary of Significant Accounting Policies - Net Loss per Share (Details) - shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders	3,044,093	62,088,366
Convertible Preferred Stock
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders		59,958,081
Employee Stock options
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders	3,044,093	2,029,402
Restricted stock
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders		100,883