Leases (Components of Lease Cost) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 10	$ 21
Finance lease cost:
Amortization of right-of-use assets	2	3
Interest of lease liabilities	0	0
Total finance lease cost	2	3
Variable lease cost	1	6
Short-term lease cost	3	5
Total lease cost	16	35
DTE Electric
Lessee, Lease, Description [Line Items]
Operating lease cost	4	8
Finance lease cost:
Amortization of right-of-use assets	2	3
Interest of lease liabilities	0	0
Total finance lease cost	2	3
Variable lease cost	0	0
Short-term lease cost	0	1
Total lease cost	$ 6	$ 12