Significant Accounting Policies Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2013
Accounting Policies [Abstract]
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income Comprehensive income is the change in common shareholder’s equity during a period from transactions and events from non-owner sources, including net income. As shown in the following tables, amounts recorded to accumulated other comprehensive loss for the three and six months ended June 30, 2013 reflected changes in benefit obligations.
Income Tax, Policy [Policy Text Block]	Income Taxes The Company's effective tax rate from continuing operations for the three months ended June 30, 2013 was 34 percent as compared to 37 percent for the three months ended June 30, 2012. The Company's effective tax rate from continuing operations for the six months ended June 30, 2013 was 35 percent as compared to 37 percent for the six months ended June 30, 2012. The decrease in the effective tax rate in 2013 is due primarily to higher production tax credits. The Company had $3 million of unrecognized tax benefits at June 30, 2013, that, if recognized, would favorably impact its effective tax rate. The Company does not anticipate any material changes to the unrecognized tax benefits in the next twelve months.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Stock-Based Compensation The Company received an allocation of costs from DTE Energy associated with stock-based compensation of $19 million and $11 million for the three months ended June 30, 2013 and June 30, 2012, respectively

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

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