Retirement Benefits and Trusteed Assets (OPEB - Postretirement Cost Inclusions) (Details) - Other postretirement benefit plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 22	$ 27	$ 27
Interest cost	70	69	73
Expected return on plan assets	(96)	(143)	(130)
Amortization of:
Net actuarial loss	12	11	13
Prior service credit	(9)	0	(14)
Net pension cost/other postretirement cost (credit)	(1)	(36)	(31)
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Service cost	16	20	20
Interest cost	53	53	56
Expected return on plan assets	(65)	(98)	(90)
Amortization of:
Net actuarial loss	5	8	8
Prior service credit	(7)	0	(10)
Net pension cost/other postretirement cost (credit)	$ 2	$ (17)	$ (16)