Summary of Significant Accounting Policies - Net Loss per Share (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders	5,695,219	3,753,025
Stock options
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders	4,616,395	3,753,025
Unvested Restricted Stock
Anti-dilutive securities
Total shares excluded from diluted net loss per share applicable to common stockholders	1,078,824