Supplemental Cash Flow Information (Reconciliation of Cash, Cash Equivalents and Restricted Cash to Statement of Cash Flows) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 126,619	$ 53,336	$ 67,670
Restricted cash	1,858	1,612	3,486
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 128,477	$ 54,948	$ 71,156	$ 40,471