Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Comprehensive loss	$ 20,923	$ 21,634	$ 64,616	$ 62,855
Restricted cash	1,500		$ 1,500			$ 1,500
Number of operating segments | segment			1
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	11,192		$ 11,192
Operating lease liability	$ 12,110		$ 12,110
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets					$ 12,700
Operating lease liability					$ 13,900