Dispositions and Impairments (Financial Results That Have Been Reclassified from Continuing Operations and Included in Discontinued Operations) (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021
Other (Income) and Deductions
Income (Loss) from Discontinued Operations, Net of Taxes	$ (33,000,000)	$ 107,000,000	$ 112,000,000	$ 257,000,000
Less: Net Income Attributable to Noncontrolling Interests	0	3,000,000	6,000,000	8,000,000
Net Income (Loss) from Discontinued Operations	(33,000,000)	104,000,000	106,000,000	249,000,000
Transaction costs	30,000,000	0	59,000,000	0	$ 67,000,000
DT Midstream | Discontinued operations, spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues — Non-utility operations	0	204,000,000	405,000,000	546,000,000
Operating Expenses
Cost of gas and other — non-utility	0	6,000,000	15,000,000	14,000,000
Operation and maintenance	30,000,000	32,000,000	124,000,000	80,000,000
Depreciation and amortization	0	38,000,000	82,000,000	110,000,000
Taxes other than income	0	3,000,000	13,000,000	12,000,000
Asset (gains) losses and impairments, net	0	(4,000,000)	17,000,000	(4,000,000)
Operating Expenses	30,000,000	75,000,000	251,000,000	212,000,000
Operating Income (Loss)	(30,000,000)	129,000,000	154,000,000	334,000,000
Other (Income) and Deductions
Interest expense	0	29,000,000	50,000,000	82,000,000
Interest income	0	(4,000,000)	(4,000,000)	(6,000,000)
Other income	0	(45,000,000)	(62,000,000)	(98,000,000)
Other (Income) and Deductions	0	(20,000,000)	(16,000,000)	(22,000,000)
Income (Loss) from Discontinued Operations Before Income Taxes	(30,000,000)	149,000,000	170,000,000	356,000,000
Income Tax Expense	3,000,000	42,000,000	58,000,000	99,000,000
Income (Loss) from Discontinued Operations, Net of Taxes	(33,000,000)	107,000,000	112,000,000	257,000,000
Less: Net Income Attributable to Noncontrolling Interests	0	3,000,000	6,000,000	8,000,000
Net Income (Loss) from Discontinued Operations	$ (33,000,000)	$ 104,000,000	$ 106,000,000	$ 249,000,000