Supplemental Cash Flow Information (Reconciliation of Cash, Cash Equivalents and Restricted Cash to Statement of Cash Flows) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 67,670	$ 35,594	$ 79,583
Restricted cash	3,486	4,877	3,078
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 71,156	$ 40,471	$ 82,661	$ 67,633