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
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 245,406	$ 147,449	$ 87,212
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	247,840	$ 149,804	89,667	$ 107,099
Prepaid expenses and other current assets
Summary Of Significant Accounting Policies [Line Items]
Prepaid expenses and other current assets	395		363
Other assets
Summary Of Significant Accounting Policies [Line Items]
Other assets	$ 2,039		$ 2,092