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Fair Value (Gains and Losses and Proceeds from the Sale of Securities by the Nuclear Decommissioning Trust Funds) (Details) - DTE Electric - Nuclear decommissioning trust fund - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Debt Securities, Available-for-sale [Line Items]        
Realized gains $ 35 $ 103 $ 59 $ 134
Realized losses (6) (76) (8) (92)
Proceeds from sale of securities $ 366 $ 799 $ 637 $ 1,238