Annual report pursuant to Section 13 and 15(d)

Property and Equipment, Net (Unevaluated Property Costs not Subject to Amortization) (Details)

v3.20.4
Property and Equipment, Net (Unevaluated Property Costs not Subject to Amortization) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Abstract]        
Unevaluated property costs $ 113,078 $ 680,456 $ 439,478 $ 500,238
Unevaluated property costs, total $ 1,733,250 $ 1,986,124