Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross carrying value	$ 938	$ 938
Accumulated Amortization	(110)	(96)
Finite-lived intangible assets, net carrying value	828	842
Intangible assets, gross carrying value	959	963
Intangible assets, net carrying value	849	867
DTE Electric
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	0	0
Intangible assets, gross carrying value	21	25
Intangible assets, net carrying value	21	25
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	21	25
DTE Electric renewable energy credits | DTE Electric
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	20	24
DTE Electric emission allowances | DTE Electric
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	1	1
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross carrying value	779	770
Accumulated Amortization	(44)	(24)
Finite-lived intangible assets, net carrying value	$ 735	746
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	$ 159	168
Accumulated Amortization	(66)	(72)
Finite-lived intangible assets, net carrying value	$ 93	$ 96
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