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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, 2018
Mar. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Realized gains $ 23 $ 23
Realized losses (9) (8)
Proceeds from sale of securities $ 336 $ 394