Subsequent Events - Additional Information (Details) $ in Millions		3 Months Ended	6 Months Ended
	Aug. 10, 2018 USD ($) ft² Employee	Sep. 30, 2018 USD ($)	Jun. 30, 2018	Aug. 08, 2018 USD ($)
August 2018 Reduction in Force | Scenario Forecast
Subsequent Event [Line Items]
Total expenses relating to the reduction		$ 0.6
August 2018 Lease Amendment
Subsequent Event [Line Items]
Lease agreement extension description			The Company has the option to extend the term for one additional five-year period upon the Company’s written notice to the Lessor at least nine months and no more than 12 months in advance of the extension.
Subsequent Event
Subsequent Event [Line Items]
Current office space under lease agreement | ft²	5,711
Original office space under lease agreement | ft²	10,290
Base rent obligation	$ 0.3
Total Cash obligation	1.3
Security deposit	0.3
Relocation payment to lessor	$ 0.1
Subsequent Event | August 2018 Reduction in Force
Subsequent Event [Line Items]
Number of eliminated positions | Employee	19
Percentage of eliminated positions	44.00%
Subsequent Event | August 2018 Lease Amendment
Subsequent Event [Line Items]
Current office space under lease agreement | ft²	5,711
Original office space under lease agreement | ft²	10,290
Lease agreement origination date	Jan. 01, 2019
Lease expiration date	Dec. 31, 2023
Additional office space under lease agreement | ft²	4,000
Base rent obligation	$ 0.3
Total Cash obligation	1.3
Security deposit	0.3
Relocation payment to lessor	$ 0.1
Subsequent Event | Gates Foundation | August 2018 Grant Agreement
Subsequent Event [Line Items]
Grant receivable				$ 1.1