Derivatives and Risk Management (Schedule of Derivative Instruments Notional Amount, Weighted Average Contract Prices and Fair Value) (Details) - Not Designated as Hedging Instrument bbl in Thousands, Mcf in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) $ / bbl $ / MMBTU Mcf bbl
Financial protection on production - 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	274
Fair value	$ (818)
Financial protection on production - 2021 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,376
Fair value	$ (32)
Financial protection on production - 2021 | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,630
Fair value	$ (20)
Fixed Price Swaps - 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	102
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.83
Fair value	$ (314)
Fixed Price Swaps - 2021 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	780
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	48.94
Fair value	$ (20)
Fixed Price Swaps - 2021 | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,483
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	9.74
Fair value	$ (19)
Fixed Price Swaps - 2021 | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,107
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	23.98
Fair value	$ (74)
Fixed Price Swaps - 2021 | Normal Butane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	617
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	29.08
Fair value	$ (22)
Fixed Price Swaps - 2021 | Natural Gasoline
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	635
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	43.62
Fair value	$ (19)
Two-way Costless Collars-2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	88
Fair value	$ (253)
Two-way Costless Collars-2021 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	46
Fair value	$ (1)
Two-way Costless Collars-2021 | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	147
Fair value	$ (1)
Two-way Costless Collars - 2021 Sold Calls | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.04
Two-way Costless Collars - 2021 Sold Calls | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	45.50
Two-way Costless Collars - 2021 Sold Calls | Ethane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	10.40
Three-way Costless-collars - 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	84
Fair value	$ (251)
Three-way Costless-collars - 2021 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	550
Fair value	$ (11)
Three-Way Costless Collars - 2021 Sold Calls | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.91
Three-Way Costless Collars - 2021 Sold Calls | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	54.35
Financial protection on production - 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1,013
Fair value	$ (1,614)
Financial protection on production - 2022 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,583
Fair value	$ (73)
Financial protection on production - 2022 | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,496
Fair value	$ (17)
Financial protection on production - 2022 | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,776
Fair value	$ (89)
Fixed Price Swaps - 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	539
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.77
Fair value	$ (868)
Fixed Price Swaps - 2022 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,203
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	53.54
Fair value	$ (53)
Fixed Price Swaps - 2022 | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,361
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	10.01
Fair value	$ (16)
Fixed Price Swaps - 2022 | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,471
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	26.96
Fair value	$ (84)
Fixed Price Swaps - 2022 | Normal Butane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,295
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	29.16
Fair value	$ (28)
Fixed Price Swaps - 2022 | Natural Gasoline
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,256
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	46.41
Fair value	$ (26)
Two Way Costless Collars - 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	141
Fair value	$ (253)
Two Way Costless Collars - 2022 | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	135
Fair value	$ (1)
Two Way Costless Collars - 2022 Sold Calls | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.06
Two Way Costless Collars - 2022 Sold Calls | Ethane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	9.66
Three-Way Costless Collars - 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	333
Fair value	$ (493)
Three-Way Costless Collars - 2022 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,380
Fair value	$ (20)
Three-Way Costless Collars - 2022 | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	305
Fair value	$ (5)
Three-way Costless Collars 2022 - Sold Calls | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.94
Three-way Costless Collars 2022 - Sold Calls | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	57.05
Three-way Costless Collars 2022 - Sold Calls | Propane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	31.92
Financial protection on production- 2023 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	572
Fair value	$ (394)
Financial protection on production- 2023 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,114
Fair value	$ (23)
Fixed Price Swaps 2023 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	274
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.76
Fair value	$ (192)
Fixed Price Swaps 2023 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	846
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	55.98
Fair value	$ (7)
Two Way Costless Collars 2023 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	83
Fair value	$ (43)
Two Way Costless Collars Sold Calls 2023 | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.92
Three Way Costless Collars - 2023 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	215
Fair value	$ (159)
Three Way Costless Collars - 2023 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,268
Fair value	$ (16)
Three Way Costless Collars - 2023 Sold Calls | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.00
Three Way Costless Collars - 2023 Sold Calls | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	56.12
Financial protection on production- 2024 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	68
Fair value	$ (48)
Fixed Price Swaps 2024 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	57
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.43
Fair value	$ (42)
Fixed Price Swaps 2024 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	54
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	53.15
Fair value	$ 0
Three Way Costless Collars 2024 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	11
Fair value	$ (6)
Three Way Costless Collars Sold Calls 2024 | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.54
Basis Swaps | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	607
Fair value	$ 42
Basis Swaps - 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	71
Basis differential per MMBtu | $ / MMBTU	(0.36)
Fair value	$ 19
Basis Swaps - 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	284
Basis differential per MMBtu | $ / MMBTU	(0.38)
Fair value	$ 17
Basis Swap - 2023 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	197
Basis differential per MMBtu | $ / MMBTU	(0.49)
Fair value	$ 2
Basis Swap - 2024 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	46
Basis differential per MMBtu | $ / MMBTU	(0.71)
Fair value	$ 3
Basis Swap - 2025 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	9
Basis differential per MMBtu | $ / MMBTU	(0.64)
Fair value	$ 1
Call options | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	151
Fair value	$ (216)
Call Options 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	19
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.19
Fair value	$ (52)
Call Options 2021 | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	57
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	60.00
Fair value	$ (1)
Call Options 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	77
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.00
Fair value	$ (118)
Call Options 2023 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	46
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.94
Fair value	$ (37)
Call Options 2024 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	9
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.00
Fair value	$ (9)
Put options | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	10
Fair value	$ 0
Put Option 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	5
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.00
Fair value	$ 0
Put Option 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	5
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.00
Fair value	$ 0
Swaption 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	18
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.00
Fair value	$ (26)
Storage 2021
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Fair value	$ 1
Purchased Fixed Price Swaps, Storage, 2021
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.20
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 1
Purchased Basis Swaps Storage, 2021
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.88)
Fair value	$ 0
Fixed Price Swap, Storage, 2021
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.17
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Basis Swaps Storage, 2021
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.57)
Fair value	$ 0
Storage 2022
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	3
Fair value	$ (4)
Purchased Fixed Price Swaps, Storage, 2022
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.14
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 1
Fixed Price Swap, Storage, 2022
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	2
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.82
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ (5)
Basis Swaps Storage, 2022
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.57)
Fair value	$ 0
Purchased Fixed Price Swaps, Marketing, 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.44
Fair value	$ 2
Sold Puts | Three-Way Costless Collars - 2021 Sold Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.19
Sold Puts | Three-Way Costless Collars - 2021 Sold Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	39.18
Sold Puts | Three-Way Costless Collars - 2022 Sold Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.06
Sold Puts | Three-Way Costless Collars - 2022 Sold Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	39.89
Sold Puts | Three-Way Costless Collars - 2022 Sold Puts | Propane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	16.80
Sold Puts | Three Way Costless Collars - 2023 Sold Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.09
Sold Puts | Three Way Costless Collars - 2023 Sold Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	33.97
Sold Puts | Three Way Costless Collars Sold Puts 2024 | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.25
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.70
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	37.50
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Ethane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	7.14
Purchased Puts | Three-Way Costless Collars - 2021 Purchased Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.54
Purchased Puts | Three-Way Costless Collars - 2021 Purchased Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	48.95
Purchased Puts | Two Way Costless Collars - 2022 Purchased Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.66
Purchased Puts | Two Way Costless Collars - 2022 Purchased Puts | Ethane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	7.56
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.51
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	50.23
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Propane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	21.00
Purchased Puts | Two Way Costless Collars Purchased Puts 2023 | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.69
Purchased Puts | Three Way Costless Collars - 2023 Purchased Puts | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.54
Purchased Puts | Three Way Costless Collars - 2023 Purchased Puts | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	45.51
Purchased Puts | Three Way Costless Collars Purchased Puts 2024 | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.80