Summary of Significant Accounting Policies (Restricted Cash) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 188,550	$ 50,436	$ 123,062
Restricted cash	3,000	3,000	3,000
Total cash, cash equivalents and restricted cash in the Condensed Statements of Cash Flows	$ 191,550	$ 53,436	$ 126,062	$ 126,575