Leases (Components of Lease Cost) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 11
Finance lease cost:
Amortization of right-of-use assets	1
Interest of lease liabilities	0
Total finance lease cost	1
Variable lease cost	5
Total lease cost	17
DTE Electric
Lessee, Lease, Description [Line Items]
Operating lease cost	4
Finance lease cost:
Amortization of right-of-use assets	1
Interest of lease liabilities	0
Total finance lease cost	1
Variable lease cost	0
Total lease cost	$ 5