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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, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Schedule of Available-for-sale Securities [Line Items]        
Realized gains $ 14 $ 13 $ 63 $ 59
Realized losses (7) (8) (23) (48)
Proceeds from sale of securities $ 246 $ 394 $ 951 $ 1,135