Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Major Customers) (Details)

v3.19.3.a.u2
Summary of Significant Accounting Policies (Major Customers) (Details) - Revenue Benchmark - Customer Concentration Risk
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Rio Energy International, Inc.      
Product Information [Line Items]      
Concentration risk, percentage 26.00% 28.00% 17.00%
Enterprise Crude Oil, LLC      
Product Information [Line Items]      
Concentration risk, percentage 19.00% 14.00% 18.00%
Plains Marketing, L.P.      
Product Information [Line Items]      
Concentration risk, percentage 15.00% 21.00% 29.00%
Shell Trading Company      
Product Information [Line Items]      
Concentration risk, percentage 10.00%