Significan Accounting Policies (Details Textuals 1) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2010
Federal Income Tax Note [Line Items]
Effective Income Tax Rate, Continuing Operations	35.00%		36.00%	24.00%	34.00%
Income Tax Expense (Benefit)	$ 101,000,000	$ 88,000,000	$ 92,000,000	$ 180,000,000	$ 252,000,000
Unrecognized Tax Benefits	4,000,000			4,000,000			5,000,000
Unrecognized Tax Benefits, Period Increase (Decrease)				40,000,000
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit						49,000,000
Michigan Corporate Income Tax		6.00%
Deferred Tax Liabilities Attributable to Regulated Utilities								41,000,000
Reduction of Net Deferred Tax Assets		0
Reduction of Net Deferred Tax Assets		307,000,000
Decrease in Deferred Tax Liabilities Attributaable to Regulated Utilities		395,000,000
Consistnet with Orginal Treatment of Deferred Tax Liabilities No Cash Flow Impact		$ 0