Retirement Benefits and Trusteed Assets (OPEB - Postretirement Cost Inclusions) (Details) - Other postretirement benefit plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 27	$ 27	$ 27
Interest cost	69	73	80
Expected return on plan assets	(143)	(130)	(129)
Amortization of:
Net actuarial loss	11	13	30
Prior service credit	0	(14)	(118)
Other	0	0	(1)
Net pension cost/other postretirement credit	(36)	(31)	(111)
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Service cost	20	20	20
Interest cost	53	56	61
Expected return on plan assets	(98)	(90)	(90)
Amortization of:
Net actuarial loss	8	8	21
Prior service credit	0	(10)	(89)
Net pension cost/other postretirement credit	$ (17)	$ (16)	$ (77)