Retirement Benefits and Trusteed Assets (OPEB - Accumulated Postretirement Obligations in Excess of Plan Assets) (Details) - Other postretirement benefit plan - USD ($) $ in Millions |
Dec. 31, 2021 |
Dec. 31, 2020 |
---|---|---|
Defined Benefit Plan Disclosure [Line Items] | ||
Accumulated postretirement benefit obligation | $ 822 | $ 878 |
Fair value of plan assets | 463 | 470 |
Accumulated postretirement benefit obligation in excess of plan assets | 359 | 408 |
DTE Electric | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Accumulated postretirement benefit obligation | 775 | 826 |
Fair value of plan assets | 435 | 442 |
Accumulated postretirement benefit obligation in excess of plan assets | $ 340 | $ 384 |