Derivative Financial Instruments (Oil Derivative Contracts Volume And Weighted Average Price) (Details)	Dec. 31, 2020 bbl / d $ / bbl $ / MMBTU
Brent Swap Contracts for First Quarter of year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	85,000
Brent Swap Contracts for First Quarter of year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	46.88
Brent Swap Contracts for Second Quarter of year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	85,000
Brent Swap Contracts for Second Quarter of year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	46.88
Brent Swap Contracts for Third Quarter of year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	0
Brent Swap Contracts for Third Quarter of year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	0
Brent Swap Contracts for Fourth Quarter of year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	0
Brent Swap Contracts for Fourth Quarter of year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	0
Brent Swap Contracts for year Two [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	0
Brent Swap Contracts for year Two [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	0
Brent Collar Contracts With Short Puts for First Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	90,000
Brent Collar Contracts With Short Puts for First Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Ceiling, price per barrel | $ / bbl	50.74
Floor, price per barrel | $ / bbl	45.11
Short put, price per barrel | $ / bbl	35.07
Brent Collar Contracts With Short Puts for Second Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	90,000
Brent Collar Contracts With Short Puts for Second Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Ceiling, price per barrel | $ / bbl	50.74
Floor, price per barrel | $ / bbl	45.11
Short put, price per barrel | $ / bbl	35.07
Brent Collar Contracts With Short Puts for Third Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	90,000
Brent Collar Contracts With Short Puts for Third Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Ceiling, price per barrel | $ / bbl	50.74
Floor, price per barrel | $ / bbl	45.11
Short put, price per barrel | $ / bbl	35.07
Brent Collar Contracts With Short Puts for Fourth Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	90,000
Brent Collar Contracts With Short Puts for Fourth Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Ceiling, price per barrel | $ / bbl	50.74
Floor, price per barrel | $ / bbl	45.11
Short put, price per barrel | $ / bbl	35.07
Brent Collar Contracts With Short Puts for Year Two [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	20,000
Brent Collar Contracts With Short Puts for Year Two [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Ceiling, price per barrel | $ / bbl	57.88
Floor, price per barrel | $ / bbl	45.50
Short put, price per barrel | $ / bbl	35.00
Brent call contracts sold for First Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	20,000
Brent call contracts sold for First Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	69.74
Brent call contracts sold for Second Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	20,000
Brent call contracts sold for Second Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	69.74
Brent call contracts sold for Third Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	20,000
Brent call contracts sold for Third Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	69.74
Brent call contracts sold for Fourth Quarter of Year One [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	20,000
Brent call contracts sold for Fourth Quarter of Year One [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	69.74
Brent call contracts sold for Year Two [Member] | Oil contracts
Trading Activity, Gains and Losses, Net [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl / d	0
Brent call contracts sold for Year Two [Member] | Oil contracts, price per bbl
Trading Activity, Gains and Losses, Net [Line Items]
Price per MMBtu in usd | $ / MMBTU	0