Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 159	$ 168
Less accumulated amortization	59	57
Intangible assets, net	100	111
Less current intangible assets	11	9
Intangible assets	89	102
Emission allowances
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, gross	1	1
DTE Electric
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	50	46
Less current intangible assets	11	9
Intangible assets	39	37
DTE Electric | Emission allowances
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, gross	1	1
Renewable energy credits
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	49	45
Renewable energy credits | DTE Electric
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	49	45
Contract intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 109	$ 122