Significant Accounting Policies Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	$ 26	$ 14	$ 77	$ 49
Income from REF entities	20	20	60	59
Gains from trading securities	6	5	19	15
Allowance for equity funds used during construction	5	5	17	15
Contract services	9	5	17	16
Other	8	2	14	6
Total other income	74	51	204	160
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	0	0	1	1
Gains from trading securities	6	5	19	15
Allowance for equity funds used during construction	4	4	14	13
Contract services	9	5	18	16
Other	2	1	5	3
Total other income	$ 21	$ 15	$ 57	$ 48