Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - 2016 Employee Stock Purchase Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 434	$ 164	$ 963	$ 348
Research and Development
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	190	43	400	129
General and Administrative
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 244	$ 121	$ 563	$ 219