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, 2017	Dec. 31, 2016
Other changes in plan assets and accumulated postretirement benefit obligation recognized in Regulatory assets and Other comprehensive income (loss)
Net actuarial gain	$ (21)	$ (68)
Amortization of net actuarial loss	(13)	(30)
Prior service credit	(1)	0
Amortization of prior service credit	14	119
Total recognized in Regulatory assets and Other comprehensive income (loss)	(21)	21
Total recognized in net periodic pension cost, Regulatory assets, and Other comprehensive income (loss)	(52)	(90)
Estimated amounts to be amortized from Regulatory assets and Accumulated other comprehensive income (loss) into net periodic benefit cost during next fiscal year
Net actuarial loss	11	16
Prior service credit	(1)	(14)
DTE Electric
Other changes in plan assets and accumulated postretirement benefit obligation recognized in Regulatory assets and Other comprehensive income (loss)
Net actuarial gain	2	(59)
Amortization of net actuarial loss	(8)	(21)
Amortization of prior service credit	10	89
Total recognized in Regulatory assets and Other comprehensive income (loss)	4	9
Total recognized in net periodic pension cost, Regulatory assets, and Other comprehensive income (loss)	(12)	(68)
Estimated amounts to be amortized from Regulatory assets and Accumulated other comprehensive income (loss) into net periodic benefit cost during next fiscal year
Net actuarial loss	8	10
Prior service credit	$ 0	$ (10)