Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Summary of Significant Accounting Policies (Reconciliation of Cash, Cash Equivalents, and Restricted Cash) (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]        
Cash and cash equivalents $ 47,853 $ 45,917    
Restricted cash - current 86 911    
Restricted cash - non-current 925 925    
Abandonment funding 12,453 11,371    
Total cash, cash equivalents and restricted cash $ 61,317 $ 59,124 $ 46,655 $ 32,286