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
Accounting Policies [Abstract]
Cash and cash equivalents	$ 285,185	$ 57,937	[1]
Restricted cash	203	203	[1]
Cash, cash equivalents and restricted cash	$ 285,388	$ 58,140		$ 76,271	$ 71,267

[1] The Condensed Consolidated Balance Sheet as of December 31, 2019 has been derived from the audited financial statements as of that date.