Significant Accounting Policies Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	$ 25	$ 20	$ 51	$ 35
Income from REF entities	22	20	40	39
Gains from trading securities	5	5	13	10
Allowance for equity funds used during construction	5	5	12	10
Contract services	4	5	8	11
Other	5	2	6	4
Total other income	66	57	130	109
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	1	1	1	1
Gains from trading securities	5	5	13	10
Allowance for equity funds used during construction	4	5	10	9
Contract services	5	5	9	11
Other	2	1	3	2
Total other income	$ 17	$ 17	$ 36	$ 33