Balance Sheet Components - Other Long-Term Liabilities (Additional Information) (Details) - USD ($) $ in Thousands	76 Months Ended
	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Grants receivable				$ 16,500
Proceeds from government grants	$ 12,000
Grant agreement, recapture provision repayments		$ 1,500	$ 1,500
Delaware grant		10,469	10,469
Managed services liabilities		$ 29,741	$ 31,087