Balance Sheet Components - Other Long-Term Liabilities (Additional Information) (Details) - USD ($) $ in Thousands	76 Months Ended	97 Months Ended
	Jun. 30, 2018	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Grants receivable				$ 16,500
Proceeds from government grants	$ 12,000	$ 12,000
Grant agreement, recapture provision repayments		1,500
Delaware grant		$ 10,469	$ 10,469