Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 158	$ 168
Less accumulated amortization	57	57
Intangible assets, net	101	111
Less current intangible assets	11	9
Intangible assets	90	102
DTE Electric
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	49	46
Less current intangible assets	11	9
Intangible assets	38	37
Renewable energy credits
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	48	45
Renewable energy credits | DTE Electric
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	48	45
Contract intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	109	122
Emission allowances
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, gross	1	1
Emission allowances | DTE Electric
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets, gross	$ 1	$ 1