Summary of Significant Accounting Policies (Restricted Cash) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 97,187	$ 50,436	$ 64,093
Restricted cash	3,000	3,000	3,000
Total cash, cash equivalents and restricted cash in the Condensed Statements of Cash Flows	$ 100,187	$ 53,436	$ 67,093	$ 126,575