Retirement Benefits and Trusteed Assets (OPEB - Benefits related to Qualified and Nonqualified Pension Plans Expected to be paid in the Next Ten Years) (Details) - Other postretirement benefit plan $ in Millions	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
2018	$ 94
2019	99
2020	103
2021	105
2022	108
2023-2027	567
Total	1,076
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
2018	73
2019	77
2020	80
2021	82
2022	84
2023-2027	437
Total	$ 833