Leases (Components of Lease Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 39	$ 41
Finance lease cost:
Amortization of right-of-use assets	5	4
Interest of lease liabilities	0	0
Total finance lease cost	5	4
Variable lease cost	10	10
Short-term lease cost	12	10
Total lease cost	66	65
DTE Electric
Lessee, Lease, Description [Line Items]
Operating lease cost	14	17
Finance lease cost:
Amortization of right-of-use assets	4	4
Interest of lease liabilities	0	0
Total finance lease cost	4	4
Variable lease cost	0	0
Short-term lease cost	6	3
Total lease cost	$ 24	$ 24