Annual report pursuant to Section 13 and 15(d)

Property and Equipment, Net (Summary of Average Realized Price of Crude Oil) (Details)

v3.20.4
Property and Equipment, Net (Summary of Average Realized Price of Crude Oil) (Details)
3 Months Ended 12 Months Ended
Mar. 31, 2021
$ / Boe
Mar. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
Sep. 30, 2020
USD ($)
Jun. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
$ / Boe
Dec. 31, 2019
USD ($)
$ / Boe
Dec. 31, 2018
USD ($)
$ / Boe
Dec. 31, 2017
$ / Boe
Property, Plant and Equipment [Line Items]                  
Impairment of evaluated oil and gas properties | $     $ 585,800,000 $ 685,000,000.0 $ 1,300,000,000 $ 2,547,241,000 $ 0 $ 0  
Average 12-month price, net of differentials           37.44 53.90 58.40 49.48
Percent increase (decrease) in 12-Month Average Realized Price           (31.00%) (8.00%) 18.00%  
Forecast                  
Property, Plant and Equipment [Line Items]                  
Impairment of evaluated oil and gas properties | $   $ 100,000,000.0              
Average 12-month price, net of differentials 40.23                
Commodity - Oil                  
Property, Plant and Equipment [Line Items]                  
Average 12-month price, net of differentials           37.44 53.90 58.40