Quarterly report pursuant to Section 13 or 15(d)

Organization and Accounting Policies (Reconciliation of Cash, Cash Equivalents, and Restricted Cash) (Details)

v3.21.2
Organization and Accounting Policies (Reconciliation of Cash, Cash Equivalents, and Restricted Cash) (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Sep. 30, 2020
Dec. 31, 2019
Organization and Accounting Policies [Abstract]        
Cash and cash equivalents $ 52,839 $ 47,853 $ 41,986  
Restricted cash - current 81 86 82  
Restricted cash - non-current 1,752 925 925  
Abandonment funding 22,281 12,453 11,885  
Total cash, cash equivalents and restricted cash $ 76,953 $ 61,317 $ 54,878 $ 59,124