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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
Mar. 31, 2020
Mar. 31, 2019
Debt Securities, Available-for-sale [Line Items]    
Realized gains $ 31 $ 11
Realized losses (16) (7)
Proceeds from sale of securities $ 439 $ 176