Organization, Basis of Presentation and Liquidity - Narrative (Details)		6 Months Ended
	Jun. 12, 2020 USD ($)	Jun. 30, 2020 USD ($) segment numberOfDivestitures numberOfPrograms	Dec. 31, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of late-stage development programs | numberOfPrograms		2
Number of operating segments | segment		1
Total cash, cash equivalents and short-term investments, estimated fair value		$ 390,249,000	$ 251,155,000
Number of discrete business divestitures | numberOfDivestitures		2
Accumulated deficit		$ 1,194,581,000	$ 1,115,457,000
Period permitted for offering	3 years
Common stock authorized for issuance and sale under Shelf Registration	$ 200,000,000.0