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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 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Schedule of Available-for-sale Securities [Line Items]        
Realized gains $ 37 $ 13 $ 46 $ 22
Realized losses (25) (5) (40) (12)
Proceeds from sales of securities $ 481 $ 194 $ 741 $ 440