Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	$ 29	$ 23
Income from REF entities	23	27
Contract services	7	8
Allowance for equity funds used during construction	6	7
Gains from equity and fixed income securities	0	17
Other	0	6
Total other income	65	88
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Contract services	7	8
Allowance for equity funds used during construction	6	6
Gains from equity and fixed income securities	0	17
Other	0	2
Total other income	$ 13	$ 33