Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross carrying value	$ 2,541	$ 2,520
Accumulated Amortization	(213)	(142)
Finite-lived intangible assets, net carrying value	2,328	2,378
Intangible assets, gross carrying value	2,552	2,535
Intangible assets, net carrying value	2,339	2,393
DTE Electric
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net carrying value	11	15
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	11	15
DTE Electric renewable energy credits | DTE Electric
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	8	15
DTE Electric zonal resource credits | DTE Electric
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	3	0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross carrying value	2,252	2,252
Accumulated Amortization	(121)	(66)
Finite-lived intangible assets, net carrying value	$ 2,131	2,186
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	25 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	40 years
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross carrying value	$ 289	268
Accumulated Amortization	(92)	(76)
Finite-lived intangible assets, net carrying value	$ 197	$ 192
Contract intangibles | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	6 years
Contract intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	26 years