Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	$ 32	$ 29
Income from REF entities	24	23
Contract services	8	7
Gains from rabbi trust securities	2	0
Allowance for equity funds used during construction	7	6
Other	3	0
Total other income	76	65
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Contract services	8	7
Gains from rabbi trust securities	2	0
Allowance for equity funds used during construction	6	6
Other	3	0
Total other income	$ 19	$ 13