Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Sep. 30, 2015	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies [Line Items]
Number of shares excluded from the computation of net loss per share		2,935,847	2,241,883
Foreign currency translation adjustment		$ 12,300			$ 11,200
Restricted cash current		5,030			10,847
Operating Lease, Liability		24,696
Lessor, Operating Lease, Term of Contract				12 months
Accounting Standards Update 2016-02 [Member]
Summary of Significant Accounting Policies [Line Items]
Operating Lease, Right-of-Use Asset				$ 12,000
Operating Lease, Liability				$ 22,000
Bill Melinda Gates Foundation [Member]
Summary of Significant Accounting Policies [Line Items]
Grant Agreement	$ 89,100	89,100
Security Deposit [Member]
Summary of Significant Accounting Policies [Line Items]
Restricted cash current		1,000			1,000
Grant Agreement [Member]
Summary of Significant Accounting Policies [Line Items]
Restricted cash current		$ 5,300			$ 10,800
Convertible Debt Securities [Member]
Summary of Significant Accounting Policies [Line Items]
Number of shares excluded from the computation of net loss per share		2,385,800
Convertible Notes Initial Conversion Price Per Share		$ 136.20