Derivatives and Risk Management (Summary of Before Tax Effect of Fair Value Hedges not Designated for Hedge Accounting) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	$ (2,015)	$ (289)	$ (2,957)	$ (273)
Total gain (loss) on settled derivatives	(388)	97	(509)	310
Non-performance risk adjustment	4	0	5	1
Total gain (loss) on derivatives	(2,399)	(192)	(3,461)	38
Purchased fixed price swaps | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(1)	4	1	4
Total gain (loss) on settled derivatives	4	(2)	5	(4)
Purchased fixed price swaps | Natural Gas Storage
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	1	1	2	0
Total gain (loss) on settled derivatives	1	0	1	0
Fixed price swaps | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(748)	(138)	(991)	(74)
Total gain (loss) on settled derivatives	(111)	61	(112)	150
Amortization of premium paid		4		8
Fixed price swaps | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	0	(20)	(81)	54
Total gain (loss) on settled derivatives	(18)	17	(63)	44
Fixed price swaps | Ethane
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(12)	(13)	(25)	(23)
Total gain (loss) on settled derivatives	(13)	(2)	(23)	6
Fixed price swaps | Propane
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(32)	(17)	(120)	(25)
Total gain (loss) on settled derivatives	(53)	2	(113)	19
Fixed price swaps | Normal Butane
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(7)	0	(41)	0
Total gain (loss) on settled derivatives	(17)	0	(33)	0
Fixed price swaps | Natural Gasoline
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	1	0	(30)	0
Total gain (loss) on settled derivatives	(16)	0	(38)	0
Two-way costless collars | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(358)	(34)	(518)	(45)
Total gain (loss) on settled derivatives	(79)	(5)	(79)	1
Two-way costless collars | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	1	(5)	0	4
Total gain (loss) on settled derivatives	(1)	4	(3)	13
Two-way costless collars | Ethane
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(1)	0	(2)	0
Total gain (loss) on settled derivatives	(1)	0	(1)	0
Two-way costless collars | Propane
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	0	(1)	0	(2)
Total gain (loss) on settled derivatives	0	0	0	2
Three-way costless collars | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(619)	(98)	(869)	(195)
Total gain (loss) on settled derivatives	(84)	0	(91)	43
Three-way costless collars | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	0	(4)	(47)	15
Total gain (loss) on settled derivatives	(10)	1	(16)	5
Three-way costless collars | Propane
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(3)	0	(5)	0
Basis swaps | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(70)	54	(23)	40
Total gain (loss) on settled derivatives	27	20	76	29
Call options | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(143)	(16)	(180)	(25)
Total gain (loss) on settled derivatives	(16)	0	(16)	0
Call options | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	0	0	(1)	1
Total gain (loss) on settled derivatives	(1)	0	(1)	0
Put options | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	0	0	1	0
Total gain (loss) on settled derivatives	0	0	(2)	0
Amortization of premium paid			2
Swaptions | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(21)	0	(24)	0
Fixed price swaps – storage | Natural Gas Storage
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	(3)	(2)	(5)	(2)
Total gain (loss) on settled derivatives	0	1	0	2
Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on unsettled derivatives	$ 0	$ 0	$ 1	$ 0