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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 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Debt Securities, Available-for-sale [Line Items]        
Realized gains $ 21 $ 38 $ 80 $ 172
Realized losses (1) (11) (9) (103)
Proceeds from sale of securities $ 217 $ 816 $ 854 $ 2,054