Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Other Nonoperating Income, by Component [Line Items]
Income from REF entities	$ 29	$ 25	$ 56	$ 48
Equity earnings of equity method investees	20	32	43	53
Gains from equity securities	7	1	24	1
Contract services	6	12	14	32
Allowance for equity funds used during construction	6	6	13	13
Other	5	6	11	16
Total other income	73	82	161	163
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Gains from equity securities	7	1	24	1
Contract services	8	13	16	33
Allowance for equity funds used during construction	6	4	12	9
Other	4	4	6	6
Total other income	$ 25	$ 22	$ 58	$ 49