Share-based Compensation - Summary of Non-cash, Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	$ 29	$ 58	$ 124	$ 215
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	14	26	59	92
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	$ 15	$ 32	$ 65	$ 123