Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Other Nonoperating Income, by Component [Line Items]
Income from REF entities	$ 40	$ 27	$ 96	$ 75
Equity earnings of equity method investees	34	46	77	99
Gains from equity securities	3	5	27	6
Contract services	7	11	21	43
Allowance for equity funds used during construction	5	7	18	20
Other	9	3	20	19
Total other income	98	99	259	262
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Gains from equity securities	3	5	27	6
Contract services	7	11	23	44
Allowance for equity funds used during construction	5	5	17	14
Other	5	2	11	8
Total other income	$ 20	$ 23	$ 78	$ 72