Retirement Benefits and Trusteed Assets (OPEB - Other Changes in Plan Assets and APBO Recognized in Regulatory Assets and OCI) (Details) - Other Postretirement Benefit Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (68)	$ 192
Amortization of net actuarial loss	(43)	(20)
Amortization of prior service credit	126	144
Total recognized in Regulatory assets and Other comprehensive income (loss)	15	316
Total recognized in net periodic pension cost, Regulatory assets, and Other comprehensive income (loss)	(84)	193
Net actuarial loss	32	43
Prior service credit	(118)	(126)
DTE Electric
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	(57)	144
Amortization of net actuarial loss	(31)	(14)
Amortization of prior service credit	95	109
Total recognized in Regulatory assets and Other comprehensive income (loss)	7	239
Total recognized in net periodic pension cost, Regulatory assets, and Other comprehensive income (loss)	(60)	153
Net actuarial loss	22	31
Prior service credit	$ (89)	$ (94)