Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 156	$ 168
Less accumulated amortization	62	57
Intangible assets, net	94	111
Less current intangible assets	5	9
Intangible assets	89	102
Emission allowances
Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	1	1
Renewable energy credits
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	38	45
Contract intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	117	122
DTE Electric
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	39	46
Less current intangible assets	5	9
Intangible assets	34	37
DTE Electric | Emission allowances
Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	1	1
DTE Electric | Renewable energy credits
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	$ 38	$ 45