Income Taxes (Tables)

3 Months Ended

Mar. 31, 2016

Income Taxes [Line Items]

Schedule Of Effective Income Tax Rates

The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2016		2015		2016		2015		2016		2015
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(8.7	)	(9.9	)	(20.7	)	(25.2	)	—		—
Effect of rate-making on property-related differences	(6.8	)	(6.1	)	(15.2	)	(14.6	)	(0.8	)	(0.6	)
Production tax credits	(6.3	)	(6.2	)	(6.7	)	(7.1	)	(6.5	)	(6.2	)
Other items, net	4.5		4.3		5.9		4.8		4.8		4.4
Overall income tax rate	17.7	%	17.1	%	(1.7	%)	(7.1	%)	32.5	%	32.6	%

Summary Of Tax Credit Carryforwards

At March 31, 2016, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

		Alliant Energy				IPL				WPL
	Earliest Expiration Date	Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets
Federal net operating losses	2030		$733		$252		$330		$111		$298		$104
State net operating losses	2018	748		39		20		1		47		2
Federal tax credits	2022	250		246		89		86		101		101
					$537				$198				$207

IPL [Member]

Income Taxes [Line Items]

Schedule Of Effective Income Tax Rates

The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2016		2015		2016		2015		2016		2015
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(8.7	)	(9.9	)	(20.7	)	(25.2	)	—		—
Effect of rate-making on property-related differences	(6.8	)	(6.1	)	(15.2	)	(14.6	)	(0.8	)	(0.6	)
Production tax credits	(6.3	)	(6.2	)	(6.7	)	(7.1	)	(6.5	)	(6.2	)
Other items, net	4.5		4.3		5.9		4.8		4.8		4.4
Overall income tax rate	17.7	%	17.1	%	(1.7	%)	(7.1	%)	32.5	%	32.6	%

Summary Of Tax Credit Carryforwards

At March 31, 2016, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

		Alliant Energy				IPL				WPL
	Earliest Expiration Date	Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets
Federal net operating losses	2030		$733		$252		$330		$111		$298		$104
State net operating losses	2018	748		39		20		1		47		2
Federal tax credits	2022	250		246		89		86		101		101
					$537				$198				$207

WPL [Member]

Income Taxes [Line Items]

Schedule Of Effective Income Tax Rates

The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2016		2015		2016		2015		2016		2015
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(8.7	)	(9.9	)	(20.7	)	(25.2	)	—		—
Effect of rate-making on property-related differences	(6.8	)	(6.1	)	(15.2	)	(14.6	)	(0.8	)	(0.6	)
Production tax credits	(6.3	)	(6.2	)	(6.7	)	(7.1	)	(6.5	)	(6.2	)
Other items, net	4.5		4.3		5.9		4.8		4.8		4.4
Overall income tax rate	17.7	%	17.1	%	(1.7	%)	(7.1	%)	32.5	%	32.6	%

Summary Of Tax Credit Carryforwards

At March 31, 2016, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

		Alliant Energy				IPL				WPL
	Earliest Expiration Date	Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets
Federal net operating losses	2030		$733		$252		$330		$111		$298		$104
State net operating losses	2018	748		39		20		1		47		2
Federal tax credits	2022	250		246		89		86		101		101
					$537				$198				$207