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	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) $ / MMBTU $ / bbl Mcf bbl	Dec. 31, 2019 USD ($)
Sold Fixed Price Swaps - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	279
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.50
Fair value	$ 181
Sold Fixed Price Swaps - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,442
Average price (in dollars per MMBtu, Bbl) | $ / bbl	57.75
Fair value	$ 66
Sold Fixed Price Swaps - 2020 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	6,952
Average price (in dollars per MMBtu, Bbl) | $ / bbl	8.59
Fair value	$ 21
Sold Fixed Price Swaps - 2020 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,049
Average price (in dollars per MMBtu, Bbl) | $ / bbl	23.06
Fair value	$ 43
Two-way Costless-collars - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	23
Fair value	$ 3
Two-way Costless-collars - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	731
Fair value	$ 19
Two-way Costless-collars - 2020 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	275
Fair value	$ 4
Two-way Costless-collars - 2020 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.79
Two-way Costless-collars - 2020 Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	59.81
Two-way Costless-collars - 2020 Sold Calls | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	29.40
Three-Way Costless Collars - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	136
Fair value	$ 15
Three-Way Costless Collars - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,210
Fair value	$ 9
Three-way Costless-collars - 2020 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.70
Three-way Costless-collars - 2020 Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	58.05
Financial protection on production - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	438
Fair value	$ 199
Financial protection on production - 2020 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,383
Fair value	$ 94
Financial protection on production - 2020 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,324
Fair value	$ 47
Sold Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	36
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.53
Fair value	$ 5
Sold Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,328
Average price (in dollars per MMBtu, Bbl) | $ / bbl	53.72
Fair value	$ 39
Sold Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,017
Average price (in dollars per MMBtu, Bbl) | $ / bbl	7.40
Fair value	$ 2
Sold Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,460
Average price (in dollars per MMBtu, Bbl) | $ / bbl	21.77
Fair value	$ 17
Two-way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	29
Two-way Costless Collars-2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Fair value	$ (1)
Two-way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.77
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	265
Fair value	$ (20)
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,445
Fair value	$ 10
Three-Way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.84
Three-Way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	58.14
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	330
Fair value	$ (16)
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,773
Fair value	$ 49
Sold Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	438
Average price (in dollars per MMBtu, Bbl) | $ / bbl	51.74
Fair value	$ 5
Two Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	29
Two Way Costless Collars - 2022 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.83
Three-Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	91
Fair value	$ (2)
Three-Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	666
Fair value	$ 4
Three-way Costless Collars 2022 - Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.86
Three-way Costless Collars 2022 - Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	58.00
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	120
Fair value	$ (2)
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,104
Fair value	$ 9
Three Way Costless Collars - 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	2
Three Way Costless Collars - 2023 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.35
Sold Basis Swaps - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	199
Basis differential per MMBtu | $ / MMBTU	(0.44)
Fair value	$ (3)
Sold Basis Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	103
Basis differential per MMBtu | $ / MMBTU	(0.03)
Fair value	$ 12
Sold Basis Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	88
Basis differential per MMBtu | $ / MMBTU	(0.48)
Fair value	$ (4)
Sold Basis Swaps | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	390
Fair value	$ 5
Sold Call Options - 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	51
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.83
Fair value	$ (2)
Sold Call Options - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	57
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.15
Fair value	$ (7)
Sold Call Options - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	226
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	60.00
Fair value	$ 0
Sold Call Options - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	58
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.00
Fair value	$ (6)
Sold Call Options - 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	17
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.84
Fair value	$ (3)
Sold Call Options - 2024 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	9
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.00
Fair value	$ (2)
Sold call options | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	192
Fair value	$ (20)
Purchased Fixed Price Swaps, Storage, 2020 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	3
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.00
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ (1)
Purchased Basis Swaps, Storage, 2020 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.49)
Fair value	$ 0
Sold Fixed Price Swaps, Storage, 2020 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	2
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	1.99
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Sold Basis Swaps, Storage, 2020 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.51)
Fair value	$ 0
Storage 2020 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	7
Fair value	$ (1)
Purchased Fixed Price Swaps, Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.04
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Fixed Price Swap, Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	2
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.49
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Sold Basis Swaps Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.38)
Fair value	$ 0
Storage 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	4
Fair value	$ 0
Purchased Fixed Price Swaps, Marketing, 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	6
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.44
Fair value	$ (2)
Purchased Fixed Price Swaps, Marketing, 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	6
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.44
Fair value	$ 0
Marketing 2020 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	12
Fair value	$ (2)
Fixed price swaps | Natural Gas
Derivative [Line Items]
Premium paid	$ 9	$ 9
Purchased fixed price swaps | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	186
Average price (in dollars per MMBtu, Bbl) | $ / bbl	57.46
Fair value	$ (5)
Sold fixed price swaps | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,628
Average price (in dollars per MMBtu, Bbl) | $ / bbl	57.73
Fair value	$ 71
Short Puts | Three-way Costless-collars - 2020 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.08
Short Puts | Three-way Costless-collars - 2020 Sold Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	43.94
Short Puts | Three-Way Costless Collars - 2021 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.18
Short Puts | Three-Way Costless Collars - 2021 Sold Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	43.52
Short Puts | Three-Way Costless Collars - 2022 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.10
Short Puts | Three-Way Costless Collars - 2022 Sold Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	42.50
Short Puts | Three Way Costless Collars - 2023 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.15
Purchased Puts | Two-way Costless-collars - 2020 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.50
Purchased Puts | Two-way Costless-collars - 2020 Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	56.88
Purchased Puts | Two-way Costless-collars - 2020 Purchased Puts | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	25.20
Purchased Puts | Three-way Costless-collars - 2020 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.42
Purchased Puts | Three-way Costless-collars - 2020 Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	53.17
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.28
Purchased Puts | Three-Way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.49
Purchased Puts | Three-Way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	53.25
Purchased Puts | Two Way Costless Collars - 2022 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.10
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.46
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	53.20
Purchased Puts | Three Way Costless Collars - 2023 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.55