Organization And Accounting Policies (Reconciliation Of Cash, Cash Equivalents, And Restricted Cash) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Organization and Accounting Policies [Abstract]
Cash and cash equivalents	$ 46,195	$ 33,360
Restricted cash - current	788	804
Restricted cash - non-current	921	920
Abandonment funding	11,390	11,571
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statements of cash flows	$ 59,294	$ 46,655	$ 44,847	$ 32,286