Supplemental Cash Flow Information (Reconciliation of Cash, Cash Equivalents and Restricted Cash to Statement of Cash Flows) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 186,683	$ 53,336	$ 64,045
Restricted cash	17,671	1,612	1,697
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 204,354	$ 54,948	$ 65,742	$ 40,471