Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2016
Restricted cash for the benefit of its leased properties	$ 1,700	$ 1,700
Restricted cash to collateralize corporate credit card		500
Restricted cash	1,700	2,300	$ 300
Restricted cash (non-current)	1,735	1,735
Restricted cash (current)		622
Cash, Cash Equivalents and Restricted Cash	93,633	309,421	104,572			$ 7,068
Change in fair value of the unvested awards	800				$ 100
Other than Temporary Impairment Losses, Investments	0	0	$ 0
Accumulated deficit
Change in fair value of the unvested awards	$ 800	$ 92
Accumulated deficit | ASU 2016-02
Change in fair value of the unvested awards				$ 800