Basis of Presentation and Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019		Jun. 30, 2019	Dec. 31, 2018
Basis of Presentation and Summary of Significant Accounting Policies
Cash and cash equivalents	$ 224,617	$ 177,668	[1]	$ 105,927
Restricted cash	0			50
Restricted cash, non-current	440	240	[1]	785
Total cash, cash equivalents and restricted cash	$ 225,057	$ 177,908		$ 106,762	$ 73,191

[1] The consolidated balance sheet as of December 31, 2019 has been derived from the audited consolidated balance sheet included in the Company’s 2019 Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 27, 2020.