Fair Value Measurements Table - Fair Value of Financial Assets and Liabilities (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Price Risk Derivative Assets, at Fair Value	$ 147	$ 384
Other Assets, Fair Value Disclosure	31	31
Assets, Fair Value Disclosure	178	415
Interest Rate Derivative Liabilities, at Fair Value	(522)	(399)
Price Risk Derivative Liabilities, at Fair Value	(204)	(389)
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(726)	(788)
Level 1
Price Risk Derivative Assets, at Fair Value	131	369
Other Assets, Fair Value Disclosure	20	20
Assets, Fair Value Disclosure	151	389
Interest Rate Derivative Liabilities, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	(198)	(383)
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(198)	(383)
Level 2
Price Risk Derivative Assets, at Fair Value	16	15
Other Assets, Fair Value Disclosure	11	11
Assets, Fair Value Disclosure	27	26
Interest Rate Derivative Liabilities, at Fair Value	(522)	(399)
Price Risk Derivative Liabilities, at Fair Value	(6)	(6)
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(528)	(405)
Commodity Derivatives - Natural Gas [Member] | Basis Swaps IFERC/NYMEX [Member]
Price Risk Derivative Assets, at Fair Value	13	17
Price Risk Derivative Liabilities, at Fair Value	(9)	(49)
Commodity Derivatives - Natural Gas [Member] | Swing Swaps IFERC [Member]
Price Risk Derivative Assets, at Fair Value	2	1
Price Risk Derivative Liabilities, at Fair Value	(4)	(1)
Commodity Derivatives - Natural Gas [Member] | Fixed Swaps/Futures [Member]
Price Risk Derivative Assets, at Fair Value	5	65
Price Risk Derivative Liabilities, at Fair Value	(29)	(43)
Commodity Derivatives - Natural Gas [Member] | Forward Physical Swaps [Member]
Price Risk Derivative Assets, at Fair Value	6	3
Commodity Derivatives - Natural Gas [Member] | Level 1 | Basis Swaps IFERC/NYMEX [Member]
Price Risk Derivative Assets, at Fair Value	13	17
Price Risk Derivative Liabilities, at Fair Value	(9)	(49)
Commodity Derivatives - Natural Gas [Member] | Level 1 | Swing Swaps IFERC [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	(1)	0
Commodity Derivatives - Natural Gas [Member] | Level 1 | Fixed Swaps/Futures [Member]
Price Risk Derivative Assets, at Fair Value	5	65
Price Risk Derivative Liabilities, at Fair Value	(29)	(43)
Commodity Derivatives - Natural Gas [Member] | Level 1 | Forward Physical Swaps [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Commodity Derivatives - Natural Gas [Member] | Level 2 | Basis Swaps IFERC/NYMEX [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Commodity Derivatives - Natural Gas [Member] | Level 2 | Swing Swaps IFERC [Member]
Price Risk Derivative Assets, at Fair Value	2	1
Price Risk Derivative Liabilities, at Fair Value	(3)	(1)
Commodity Derivatives - Natural Gas [Member] | Level 2 | Fixed Swaps/Futures [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Commodity Derivatives - Natural Gas [Member] | Level 2 | Forward Physical Swaps [Member]
Price Risk Derivative Assets, at Fair Value	6	3
Commodity Derivatives - Refined Products [Member] | Future [Member]
Price Risk Derivative Assets, at Fair Value	5	8
Price Risk Derivative Liabilities, at Fair Value	(4)	(10)
Commodity Derivatives - Refined Products [Member] | Level 1 | Future [Member]
Price Risk Derivative Assets, at Fair Value	5	8
Price Risk Derivative Liabilities, at Fair Value	(4)	(10)
Commodity Derivatives - Refined Products [Member] | Level 2 | Future [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Commodity Derivatives - Crude [Member] | Future [Member]
Price Risk Derivative Assets, at Fair Value	2
Commodity Derivatives - Crude [Member] | Forwards Swaps [Member]
Price Risk Derivative Assets, at Fair Value		13
Commodity Derivatives - Crude [Member] | Level 1 | Future [Member]
Price Risk Derivative Assets, at Fair Value	2
Commodity Derivatives - Crude [Member] | Level 1 | Forwards Swaps [Member]
Price Risk Derivative Assets, at Fair Value		13
Commodity Derivatives - Crude [Member] | Level 2 | Future [Member]
Price Risk Derivative Assets, at Fair Value	0
Commodity Derivatives - Crude [Member] | Level 2 | Forwards Swaps [Member]
Price Risk Derivative Assets, at Fair Value		0
Commodity Derivatives - Power [Member] | Forward Swaps [Member]
Price Risk Derivative Assets, at Fair Value	8	11
Price Risk Derivative Liabilities, at Fair Value	(3)	(5)
Commodity Derivatives - Power [Member] | Put Option [Member]
Price Risk Derivative Assets, at Fair Value	0	1
Commodity Derivatives - Power [Member] | Call Option [Member]
Price Risk Derivative Assets, at Fair Value	1	1
Commodity Derivatives - Power [Member] | Future [Member]
Price Risk Derivative Assets, at Fair Value	2	4
Price Risk Derivative Liabilities, at Fair Value	(2)	(3)
Commodity Derivatives - Power [Member] | Level 1 | Forward Swaps [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Commodity Derivatives - Power [Member] | Level 1 | Put Option [Member]
Price Risk Derivative Assets, at Fair Value	0	1
Commodity Derivatives - Power [Member] | Level 1 | Call Option [Member]
Price Risk Derivative Assets, at Fair Value	1	1
Commodity Derivatives - Power [Member] | Level 1 | Future [Member]
Price Risk Derivative Assets, at Fair Value	2	4
Price Risk Derivative Liabilities, at Fair Value	(2)	(3)
Commodity Derivatives - Power [Member] | Level 2 | Forward Swaps [Member]
Price Risk Derivative Assets, at Fair Value	8	11
Price Risk Derivative Liabilities, at Fair Value	(3)	(5)
Commodity Derivatives - Power [Member] | Level 2 | Put Option [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Commodity Derivatives - Power [Member] | Level 2 | Call Option [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Commodity Derivatives - Power [Member] | Level 2 | Future [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Commodity Derivatives - NGLs [Member] | Forward Swaps [Member]
Price Risk Derivative Assets, at Fair Value	103	260
Price Risk Derivative Liabilities, at Fair Value	(153)	(278)
Commodity Derivatives - NGLs [Member] | Level 1 | Forward Swaps [Member]
Price Risk Derivative Assets, at Fair Value	103	260
Price Risk Derivative Liabilities, at Fair Value	(153)	(278)
Commodity Derivatives - NGLs [Member] | Level 2 | Forward Swaps [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	$ 0	$ 0