Income Taxes (Tables)

9 Months Ended

Sep. 30, 2012

Income Tax [Line Items]

Schedule Of Effective Income Tax Rates

The effective income tax rates shown in the following table for the three and nine months ended September 30 were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Three Months				Nine Months
	2012		2011		2012		2011
Alliant Energy	20.4	%	23.5	%	24.0	%	16.6	%
IPL	(12.6	%)	(3.3	%)	(5.6	%)	(1.7	%)
WPL	35.5	%	34.4	%	37.7	%	33.0	%

Production Tax Credits (Net Of State Tax Impacts)

For the three and nine months ended September 30, production tax credits (net of state tax impacts) resulting from these wind projects were as follows (in millions):

	Three Months				Nine Months
	2012		2011		2012		2011
Cedar Ridge (WPL)		$0.7		$0.6		$3.0		$3.2
Bent Tree - Phase I (WPL)	1.8		1.4		6.0		6.7
Subtotal (WPL)	2.5		2.0		9.0		9.9
Whispering Willow - East (IPL)	2.0		1.8		8.7		8.2
		$4.5		$3.8		$17.7		$18.1

Alliant Energy [Member]

Income Tax [Line Items]

Summary Of Tax Credit Carryforwards

At September 30, 2012, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):

Alliant Energy	Carryforward Amount			Deferred Tax Assets			Earliest Expiration Date
Federal net operating losses		$828			$284		2028
Federal net operating losses offset - uncertain tax positions	(55		)	(19		)
State net operating losses	776			40			2014
State net operating losses offset - uncertain tax positions	(26		)	(2		)
Federal tax credits	128			126			2022
					$429

IPL [Member]

Income Tax [Line Items]

Summary Of Tax Credit Carryforwards

IPL	Carryforward Amount			Deferred Tax Assets			Earliest Expiration Date
Federal net operating losses		$354			$121		2028
Federal net operating losses offset - uncertain tax positions	(25		)	(9		)
State net operating losses	170			9			2022
Federal tax credits	34			34			2022
					$155

WPL [Member]

Income Tax [Line Items]

Summary Of Tax Credit Carryforwards

WPL	Carryforward Amount			Deferred Tax Assets			Earliest Expiration Date
Federal net operating losses		$379			$130		2028
Federal net operating losses offset - uncertain tax positions	(30		)	(10		)
State net operating losses	183			10			2022
State net operating losses offset - uncertain tax positions	(26		)	(2		)
Federal tax credits	36			35			2022
					$163