Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 10	$ 3	$ 9
Additions for tax positions of prior years	0	7	0
Lapse of statute of limitations	0	0	(6)
Unrecognized tax benefits, ending balance	10	10	3
DTE Electric
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	13	4	4
Additions for tax positions of prior years	0	9	0
Unrecognized tax benefits, ending balance	$ 13	$ 13	$ 4