Leases (Components of Lease Cost) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 41
Finance lease cost:
Amortization of right-of-use assets	4
Interest of lease liabilities	0
Total finance lease cost	4
Variable lease cost	10
Short-term lease cost	10
Total lease cost	65
DTE Electric
Lessee, Lease, Description [Line Items]
Operating lease cost	17
Finance lease cost:
Amortization of right-of-use assets	4
Interest of lease liabilities	0
Total finance lease cost	4
Variable lease cost	0
Short-term lease cost	3
Total lease cost	$ 24