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, 2019 USD ($) $ / MMBTU $ / bbl bbl Mcf
Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	13
Fair Value	$ (1)
Natural gas storage
Derivative [Line Items]
Fair Value	$ 1
Financial protection on production - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	496
Fair Value	$ 124
Financial protection on production - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	5,402
Fair Value	$ (3)
Financial protection on production - 2020 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume | bbl	5,112
Fair Value	$ 23
Fixed price swaps - 2020 | Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	7
Average price per MMBtu and Bbls | $ / MMBTU	2.44
Fair Value	$ (1)
Fixed price swaps - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	280
Average price per MMBtu and Bbls | $ / MMBTU	2.51
Fair Value	$ 76
Fixed price swaps - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	3,465
Average price per MMBtu and Bbls | $ / bbl	57.83
Fair Value	$ (2)
Fixed price swaps - 2020 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume | bbl	4,746
Average price per MMBtu and Bbls | $ / bbl	23.90
Fair Value	$ 21
Fixed price swaps - 2020 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	7,520
Average price per MMBtu and Bbls | $ / bbl	8.84
Fair Value	$ 11
Two-way costless collars - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	31
Floor price per MMBtu and Bbls | $ / MMBTU	2.56
Cap price per MMBtu and Bbls | $ / MMBTU	2.85
Fair Value	$ 6
Two-way costless collars - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	966
Cap price per MMBtu and Bbls | $ / bbl	59.81
Fair Value	$ 0
Two-way costless collars - 2020 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	56.89
Two-way costless collars - 2020 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume | bbl	366
Cap price per MMBtu and Bbls | $ / bbl	29.40
Fair Value	$ 2
Two-way costless collars - 2020 | Not Designated as Hedging Instrument | Propane | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	25.20
Three-way costless collars - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	185
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ 42
Three-way costless collars - 2020 | Not Designated as Hedging Instrument | Natural Gas | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.65
Three-way costless collars - 2020 | Not Designated as Hedging Instrument | Natural Gas | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.28
Three-way costless collars - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	971
Cap price per MMBtu and Bbls | $ / bbl	59.68
Fair Value	$ (1)
Three-way costless collars - 2020 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	55.12
Three-way costless collars - 2020 | Not Designated as Hedging Instrument | Oil | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	45.12
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	260
Fair Value	$ 7
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	3,029
Fair Value	$ (2)
Fixed Price Swaps - 2021 | Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	6
Average price per MMBtu and Bbls | $ / MMBTU	2.44
Fair Value	$ 0
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	30
Average price per MMBtu and Bbls | $ / MMBTU	2.54
Fair Value	$ 7
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	1,584
Average price per MMBtu and Bbls | $ / bbl	53.20
Fair Value	$ (1)
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume | bbl	2,460
Average price per MMBtu and Bbls | $ / bbl	21.77
Fair Value	$ 3
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume | bbl	2,410
Average price per MMBtu and Bbls | $ / bbl	7.53
Fair Value	$ 0
Two-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	17
Floor price per MMBtu and Bbls | $ / MMBTU	2.50
Cap price per MMBtu and Bbls | $ / MMBTU	2.83
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	213
Cap price per MMBtu and Bbls | $ / MMBTU	2.90
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Natural Gas | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.53
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Natural Gas | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.23
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	1,445
Cap price per MMBtu and Bbls | $ / bbl	58.14
Average price per MMBtu and Bbls | $ / bbl	0
Fair Value	$ (1)
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Oil | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	53.25
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Oil | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / bbl	43.52
Three-way costless collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	31
Cap price per MMBtu and Bbls | $ / MMBTU	3.15
Fair Value	$ 2
Three-way costless collars - 2022 | Not Designated as Hedging Instrument | Natural Gas | Purchased
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.69
Three-way costless collars - 2022 | Not Designated as Hedging Instrument | Natural Gas | Sold
Derivative [Line Items]
Floor price per MMBtu and Bbls | $ / MMBTU	2.30
Fixed price swaps - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume | bbl	438
Average price per MMBtu and Bbls | $ / bbl	51.74
Fair Value	$ 0
Basis swaps | Natural gas storage
Derivative [Line Items]
Volume | Mcf	1
Basis swaps | Natural gas storage | Purchased
Derivative [Line Items]
Volume | Mcf	0
Fair Value	$ 0
Basis Differential | $ / MMBTU	(0.32)
Basis swaps | Natural gas storage | Sold
Derivative [Line Items]
Volume | Mcf	0
Fair Value	$ 0
Basis Differential | $ / MMBTU	(0.32)
Basis swaps | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	329
Fair Value	$ 6
Basis Swaps - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	198
Fair Value	$ 0
Basis Differential | $ / MMBTU	(0.31)
Basis Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	86
Fair Value	$ 7
Basis Differential | $ / MMBTU	0.04
Basis Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume | Mcf	45
Fair Value	$ (1)
Basis Differential | $ / MMBTU	(0.50)
Call Option | Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	161
Fair Value	$ 3
Call Option | Natural Gas | Sold
Derivative [Line Items]
Volume | Mcf	361
Fair Value	$ (18)
Call Option - 2020 | Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	104
Cap price per MMBtu and Bbls | $ / MMBTU	3.46
Fair Value	$ 1
Call Option - 2020 | Natural Gas | Sold
Derivative [Line Items]
Volume | Mcf	173
Cap price per MMBtu and Bbls | $ / MMBTU	3.24
Fair Value	$ (3)
Call Option - 2021 | Natural Gas | Purchased
Derivative [Line Items]
Volume | Mcf	57
Cap price per MMBtu and Bbls | $ / MMBTU	3.52
Fair Value	$ 2
Call Option - 2021 | Natural Gas | Sold
Derivative [Line Items]
Volume | Mcf	115
Cap price per MMBtu and Bbls | $ / MMBTU	3.33
Fair Value	$ (6)
Call Option - 2021 | Oil | Purchased
Derivative [Line Items]
Volume | bbl	0
Cap price per MMBtu and Bbls | $ / bbl	60.00
Fair Value	$ (1)
Call Option - 2022 | Natural Gas | Sold
Derivative [Line Items]
Volume | Mcf	58
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ (5)
Call Option - 2023 | Natural Gas | Sold
Derivative [Line Items]
Volume | Mcf	6
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ (1)
Call Option - 2024 | Natural Gas | Sold
Derivative [Line Items]
Volume | Mcf	9
Cap price per MMBtu and Bbls | $ / MMBTU	3.00
Fair Value	$ (3)
Fixed Price Swaps | Natural gas storage | Purchased
Derivative [Line Items]
Volume | Mcf	0
Average price per MMBtu and Bbls | $ / MMBTU	2.37
Fair Value	$ 0
Fixed Price Swaps | Natural gas storage | Sold
Derivative [Line Items]
Volume | Mcf	1
Average price per MMBtu and Bbls | $ / MMBTU	3.06
Fair Value	$ 1