Significant Accounting Policies Significant Accounting Policies (Other Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Other Nonoperating Income, by Component [Line Items]
Equity earnings of equity method investees	$ 26	$ 15
Income from REF investees	18	19
Gains from trading securities	8	5
Allowance for equity funds used during construction	7	5
Contract services	4	6
Other	1	2
Total other income	64	52
DTE Electric
Schedule of Other Nonoperating Income, by Component [Line Items]
Gains from trading securities	8	5
Allowance for equity funds used during construction	6	4
Contract services	4	6
Other	1	1
Total other income	$ 19	$ 16