Discontinued Operations (Significant Non-cash Items and Capital Expenditures) (Details) - DT Midstream - Discontinued operations, spinoff $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Operating Activities
Depreciation and amortization	$ 41
Deferred income taxes	33
Equity earnings of equity method investees	(31)
Investing Activities
Plant and equipment expenditures — non-utility	$ (27)