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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, 2016
Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Realized gains $ 9 $ 9
Realized losses (15) (7)
Proceeds from sales of securities $ 260 $ 246