Stock-Based Compensation - Restricted Stock Units - General Information (Details) - Service Based RSUs - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Stock Options Granted to Non-Employees
Service-based restricted stock units granted to employees (in shares)	37,934	0	57,500
Shares vested (in shares)	18,966
Shares exchanged for tax-related purposes	5,961
Vested RSUs converting to common shares after exchange of shares for taxes	13,005
Stock-based compensation expense	$ 517,000
Granted (in shares)		0
Unrecognized compensation cost	$ 710,000	$ 0
Weighted-average period expected to recognize stock-based compensation expense	1 year 1 month 6 days
Vesting period (in years)	3 years
Research and development expenses
Stock Options Granted to Non-Employees
Stock-based compensation expense	$ 459,000
General and administrative expenses
Stock Options Granted to Non-Employees
Stock-based compensation expense	$ 58,000