Derivative Instruments and Hedging Activities - Amounts Recognized in Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivative, net	$ (10)	$ 8	$ 5	$ 14
Change in fair value of commodity derivatives	(15)	(2)	(17)	(3)
Realized gain on commodity derivatives	5	10	22	17
Gain (loss) on commodity derivative activity	(10)	8	5	14
Cash collateral posted	0		0
Cash collateral required if ratings are lowered	3		3
Gain (Loss) on Hedging Activity	(2)	0	(3)	0
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Hedging Activity	(2)	0	(3)	0
Natural gas | Financial futures/swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(5)	2	(2)	10
Natural gas | Financial swaptions
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(4)	0	(6)	0
Natural gas | Physical purchases/sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(1)	1	0	1
Condensate | Financial futures/swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	0	(8)	12	(29)
Condensate | Financial swaptions
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	0	0	2	0
Natural gas liquids | Financial futures/swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	$ 0	$ 13	$ (1)	$ 32