Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule of Other Nonoperating Income, by Component [Line Items]
Income from REF entities	$ 57	$ 43	$ 102	$ 95
Equity earnings of equity method investees	17	12	31	21
Contract services	6	7	21	20
Allowance for equity funds used during construction	7	6	20	19
Gains from rabbi trust securities	0	2	4	24
Other	3	5	9	9
Total other income	90	75	187	188
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Contract services	6	7	21	20
Allowance for equity funds used during construction	6	6	18	18
Gains from rabbi trust securities	0	2	4	24
Other	2	3	9	6
Total other income	$ 14	$ 18	$ 52	$ 68