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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, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Schedule of Available-for-sale Securities [Line Items]        
Realized gains $ 13 $ 8 $ 59 $ 30
Realized losses (8) (10) (48) (23)
Proceeds from sale of securities $ 394 $ 187 $ 1,135 $ 627