Common Equity And Preferred Stock (Common Stock Activity) (Details)	9 Months Ended
	Sep. 30, 2011
Common Equity And Preferred Stock
Shares outstanding, Jan. 1	110,893,901
Equity incentive plans	127,090
Other	(39,480)	[1]
Shares outstanding, Sep. 30	110,981,511

[1] Includes shares transferred from employees to Alliant Energy to satisfy tax withholding requirements in connection with the vesting of certain restricted stock under the equity incentive plans.