Organization and Accounting Policies (Reconciliation of Cash, Cash Equivalents, and Restricted Cash) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Organization and Accounting Policies [Abstract]
Cash and cash equivalents	$ 41,986	$ 45,917	$ 57,227
Restricted cash - current	82	911	769
Restricted cash - non-current	925	925	924
Abandonment funding	11,885	11,371	11,112
Total cash, cash equivalents and restricted cash	$ 54,878	$ 59,124	$ 70,032	$ 46,655