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, 2020	Dec. 31, 2019
Other changes in plan assets and accumulated postretirement benefit obligation recognized in Regulatory assets and Other comprehensive income (loss)
Net actuarial (gain) loss	$ (38)	$ 34
Amortization of net actuarial loss	(16)	(12)
Prior service credit (cost)	0	(53)
Amortization of prior service credit	19	9
Total recognized in Regulatory assets and Other comprehensive income (loss)	(35)	(22)
Total recognized in net periodic pension cost, Regulatory assets, and Other comprehensive income (loss)	(84)	(23)
DTE Electric
Other changes in plan assets and accumulated postretirement benefit obligation recognized in Regulatory assets and Other comprehensive income (loss)
Net actuarial (gain) loss	(26)	41
Amortization of net actuarial loss	(11)	(5)
Prior service credit (cost)	0	(33)
Amortization of prior service credit	14	7
Total recognized in Regulatory assets and Other comprehensive income (loss)	(23)	10
Total recognized in net periodic pension cost, Regulatory assets, and Other comprehensive income (loss)	$ (50)	$ 12