Derivatives and Risk Management (Schedule of Derivative Instruments Notional Amount, Weighted Average Contract Prices and Fair Value) (Details) bbl in Thousands, Mcf in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / bbl $ / MMBTU Mcf bbl
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	751.0
Fair Value	$ 16
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	6,631
Fair Value	$ 0
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	6,473
Fair Value	$ (10)
Fixed price swaps - 2021 | Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	6.0
Average price per MMBtu and Bbls | $ / MMBTU	2.44
Fair Value	$ 1
Fixed price swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	201.0
Average price per MMBtu and Bbls | $ / MMBTU	2.80
Fair Value	$ 29
Fixed price swaps - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	4,887
Average price per MMBtu and Bbls | $ / bbl	48.59
Fair Value	$ 1
Fixed price swaps - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	5,889
Average price per MMBtu and Bbls | $ / bbl	7.12
Fair Value	$ (10)
Fixed price swaps - 2021 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume | bbl	6,974
Average price per MMBtu and Bbls | $ / bbl	20.43
Fair Value	$ (36)
Fixed price swaps - 2021 | Not Designated as Hedging Instrument | Normal Butane
Derivative [Line Items]
Volume | bbl	2,004
Average price per MMBtu and Bbls | $ / bbl	24.97
Fair Value	$ (8)
Fixed price swaps - 2021 | Not Designated as Hedging Instrument | Natural Gasoline
Derivative [Line Items]
Volume | bbl	1,936
Average price per MMBtu and Bbls | $ / bbl	37.35
Fair Value	$ (13)
Two-way costless collars - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	237.0
Floor price per MMBtu and Bbls | $ / MMBTU	2.57
Cap price per MMBtu and Bbls | $ / MMBTU	2.95
Fair Value	$ 11
Two-way costless collars - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	201
Cap price per MMBtu and Bbls | $ / bbl	45.68
Fair Value	$ (1)
Two-way costless collars - 2021 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	37.73
Two-way costless collars - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	584
Cap price per MMBtu and Bbls | $ / bbl	10.40
Fair Value	$ 0
Two-way costless collars - 2021 | Not Designated as Hedging Instrument | Ethane | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	7.14
Three-way costless collars - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	313.0
Cap price per MMBtu and Bbls | $ / MMBTU	2.85
Fair Value	$ (24)
Three-way costless collars - 2021 | Not Designated as Hedging Instrument | Natural Gas | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.16
Three-way costless collars - 2021 | Not Designated as Hedging Instrument | Natural Gas | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.49
Three-way costless collars - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	1,543
Cap price per MMBtu and Bbls | $ / bbl	52.86
Fair Value	$ 0
Three-way costless collars - 2021 | Not Designated as Hedging Instrument | Oil | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	37.42
Three-way costless collars - 2021 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	47.22
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	378.0
Fair Value	$ (12)
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	2,155
Fair Value	$ 1
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	1,710
Fair Value	$ 0
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	112.0
Average price per MMBtu and Bbls | $ / MMBTU	2.68
Fair Value	$ 4
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	1,282
Average price per MMBtu and Bbls | $ / bbl	46.37
Fair Value	$ 0
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	1,575
Average price per MMBtu and Bbls | $ / bbl	8.69
Fair Value	$ 0
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume | bbl	2,120
Average price per MMBtu and Bbls | $ / bbl	20.23
Fair Value	$ (2)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Normal Butane
Derivative [Line Items]
Volume | bbl	667
Average price per MMBtu and Bbls | $ / bbl	22.77
Fair Value	$ (1)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gasoline
Derivative [Line Items]
Volume | bbl	643
Average price per MMBtu and Bbls | $ / bbl	37.77
Fair Value	$ (2)
Two-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	63.0
Floor price per MMBtu and Bbls | $ / MMBTU	2.52
Cap price per MMBtu and Bbls | $ / MMBTU	3.03
Fair Value	$ (1)
Two-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	135
Cap price per MMBtu and Bbls | $ / bbl	9.66
Fair Value	$ 0
Two-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Ethane | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	7.56
Three-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	203.0
Cap price per MMBtu and Bbls | $ / MMBTU	2.89
Fair Value	$ (15)
Three-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Natural Gas | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.06
Three-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Natural Gas | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.46
Three-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	873
Average price per MMBtu and Bbls | $ / bbl	0
Cap price per MMBtu and Bbls | $ / bbl	56.54
Fair Value	$ 1
Three-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Oil | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	40.25
Three-way Costless-collars - 2022 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	50.78
Three-way costless collars - 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	87.0
Cap price per MMBtu and Bbls | $ / MMBTU	2.98
Fair Value	$ 0
Three-way costless collars - 2023 | Not Designated as Hedging Instrument | Natural Gas | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.06
Three-way costless collars - 2023 | Not Designated as Hedging Instrument | Natural Gas | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.47
Three-way costless collars - 2023 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	878
Average price per MMBtu and Bbls | $ / bbl	0
Cap price per MMBtu and Bbls | $ / bbl	53.41
Fair Value	$ (1)
Three-way costless collars - 2023 | Not Designated as Hedging Instrument | Oil | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	33.52
Three-way costless collars - 2023 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	43.52
Basis swaps | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	420.0
Fair Value	$ 65
Basis Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	219.0
Basis Differential | $ / MMBTU	(0.21)
Fair Value	$ 57
Basis Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	139.0
Basis Differential | $ / MMBTU	(0.33)
Fair Value	$ 8
Basis Swaps - 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	47.0
Basis Differential | $ / MMBTU	(0.45)
Fair Value	$ 0
Basis Swaps - 2024 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	11.0
Basis Differential | $ / MMBTU	(0.60)
Fair Value	$ 0
Basis Swaps - 2025 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	4.0
Basis Differential | $ / MMBTU	(0.59)
Fair Value	$ 0
Call options | Natural Gas
Derivative [Line Items]
Volume | Mcf	207.0
Fair Value	$ (36)
Call Option - 2021 | Natural Gas
Derivative [Line Items]
Volume | Mcf	75.0
Cap price per MMBtu and Bbls | $ / MMBTU	3.19
Fair Value	$ (8)
Call Option - 2021 | Oil | Sold
Derivative [Line Items]
Volume | bbl	226
Cap price per MMBtu and Bbls | $ / bbl	60.00
Fair Value	$ 0
Call Option - 2022 | Natural Gas
Derivative [Line Items]
Volume | Mcf	77.0
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ (17)
Call Option - 2023 | Natural Gas
Derivative [Line Items]
Volume | Mcf	46.0
Cap price per MMBtu and Bbls | $ / MMBTU	2.94
Fair Value	$ (8)
Call Option - 2024 | Natural Gas
Derivative [Line Items]
Volume | Mcf	9.0
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ (3)
Put options | Natural Gas
Derivative [Line Items]
Volume | Mcf	23.0
Fair Value	$ (1)
Put Option - 2021 | Natural Gas
Derivative [Line Items]
Volume | Mcf	18.0
Cap price per MMBtu and Bbls | $ / MMBTU	2.00
Fair Value	$ (1)
Put Option - 2022 | Natural Gas
Derivative [Line Items]
Volume | Mcf	5.0
Cap price per MMBtu and Bbls | $ / MMBTU	2.00
Fair Value	$ 0
Swaptions | Natural Gas
Derivative [Line Items]
Volume | Mcf	0.1
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ (2)
Storage 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume | Mcf	4.0
Fair Value	$ 0
Purchased Fixed Price Swaps, Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume | Mcf	1.0
Average price per MMBtu and Bbls | $ / MMBTU	2.04
Basis Differential | $ / MMBTU	0
Fair Value	$ 0
Fixed Price Swap, Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume | Mcf	2.0
Average price per MMBtu and Bbls | $ / MMBTU	2.49
Basis Differential | $ / MMBTU	0
Fair Value	$ 0
Basis Swaps Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume | Mcf	1.0
Average price per MMBtu and Bbls | $ / MMBTU	0
Basis Differential | $ / MMBTU	(0.38)
Fair Value	$ 0