Income Taxes (Tables)

3 Months Ended

Mar. 31, 2012

Schedule Of Effective Income Tax Rates

	2012			2011
Alliant Energy		39.0	%		22.3	%
IPL		125.4	%		5.9	%
WPL		44.1	%		32.5	%

Production Tax Credits (Net Of State Tax Impacts)

	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Whispering Willow—East (IPL)	$	3.6	$	2.8	$	3.6	$	2.8	$	—	$	—
Bent Tree—Phase I (WPL)		1.5		2.5		—		—		1.5		2.5
Cedar Ridge (WPL)		1.3		1.5		—		—		1.3		1.5
	$	6.4	$	6.8	$	3.6	$	2.8	$	2.8	$	4.0

Alliant Energy Corporation [Member]

Summary Of Tax Credit Carryforwards

Alliant Energy	Carryforward Amount			Deferred Tax Assets			Earliest Expiration Date
Federal net operating losses	$	1,043		$	358			2028
Federal net operating losses offset—uncertain tax positions		(56	)		(20	)
State net operating losses		783			41			2014
State net operating losses offset—uncertain tax positions		(28	)		(2	)
Federal tax credits		116			114			2022
				$	491

IPL [Member]

Summary Of Tax Credit Carryforwards

IPL	Carryforward Amount			Deferred Tax Assets			Earliest Expiration Date
Federal net operating losses	$	475		$	163			2028
Federal net operating losses offset—uncertain tax positions		(25	)		(9	)
State net operating losses		189			11			2022
Federal tax credits		29			29			2022
				$	194

WPL [Member]

Summary Of Tax Credit Carryforwards

WPL	Carryforward Amount			Deferred Tax Assets			Earliest Expiration Date
Federal net operating losses	$	441		$	151			2028
Federal net operating losses offset—uncertain tax positions		(31	)		(11	)
State net operating losses		148			7			2022
State net operating losses offset—uncertain tax positions		(28	)		(2	)
Federal tax credits		30			29			2022
				$	174