Derivative Instruments and Hedging Activities - Amounts Recognized in Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on derivative, net	$ (5)	$ 16	$ 15	$ 6
Change in fair value of commodity derivatives	(12)	11	(2)	(1)
Realized gain on commodity derivatives	7	5	17	7
Gain (loss) on commodity derivative activity	(5)	16	15	6
Cash collateral posted	0		0
Cash collateral required if ratings are lowered	1		1
Gain (Loss) on Hedging Activity	(1)	0	(1)	0
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Hedging Activity	(1)	0	(1)	0
Natural gas | Financial futures/swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(1)	9	3	8
Natural gas | Financial swaptions
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(1)	0	(2)	0
Natural gas | Physical purchases/sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	0	1	1	0
Condensate | Financial futures/swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(7)	(10)	12	(21)
Condensate | Financial swaptions
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	(2)	0	2	0
Natural gas liquids | Financial futures/swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on commodity derivative activity	$ 6	$ 16	$ (1)	$ 19