Fair Value (Gains and Losses and Proceeds from the Sale of Securities by the Nuclear Trust Funds) (Details) - DTE Electric - Nuclear decommissioning trust fund - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Realized gains	$ 8	$ 8	$ 30	$ 24
Realized losses	(10)	(3)	(23)	(14)
Proceeds from sales of securities	$ 187	$ 177	$ 627	$ 652