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, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
2021	$ 82
2022	87
2023	91
2024	92
2025	95
2026-2030	497
Total	944
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
2021	62
2022	66
2023	69
2024	70
2025	72
2026-2030	376
Total	$ 715