Income Taxes (Tables)

6 Months Ended

Jun. 30, 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 June 30	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	(7.9	)	(10.6	)	(16.6	)	(25.3	)	—		—
Production tax credits	(5.7	)	(6.5	)	(5.3	)	(7.2	)	(6.3	)	(6.9	)
Effect of rate-making on property-related differences	(4.9	)	(8.4	)	(8.8	)	(22.3	)	(1.0	)	(0.7	)
Other items, net	0.7		4.1		(2.0	)	5.3		4.5		4.5
Overall income tax rate	17.2	%	13.6	%	2.3	%	(14.5	%)	32.2	%	31.9	%

	Alliant Energy				IPL				WPL
Six Months Ended June 30	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	(8.4	)	(10.2	)	(19.0	)	(25.2	)	—		—
Production tax credits	(6.0	)	(6.4	)	(6.1	)	(7.1	)	(6.4	)	(6.5	)
Effect of rate-making on property-related differences	(5.9	)	(7.0	)	(12.5	)	(16.6	)	(0.9	)	(0.6	)
Other items, net	2.8		4.3		2.6		4.9		4.7		4.4
Overall income tax rate	17.5	%	15.7	%	—	%	(9.0	%)	32.4	%	32.3	%

Summary Of Tax Credit Carryforwards

At June 30, 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		$769		$264		$349		$117		$311		$109
State net operating losses	2018	747		39		20		1		38		2
Federal tax credits	2022	258		254		93		90		105		105
					$557				$208				$216

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 June 30	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	(7.9	)	(10.6	)	(16.6	)	(25.3	)	—		—
Production tax credits	(5.7	)	(6.5	)	(5.3	)	(7.2	)	(6.3	)	(6.9	)
Effect of rate-making on property-related differences	(4.9	)	(8.4	)	(8.8	)	(22.3	)	(1.0	)	(0.7	)
Other items, net	0.7		4.1		(2.0	)	5.3		4.5		4.5
Overall income tax rate	17.2	%	13.6	%	2.3	%	(14.5	%)	32.2	%	31.9	%

	Alliant Energy				IPL				WPL
Six Months Ended June 30	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	(8.4	)	(10.2	)	(19.0	)	(25.2	)	—		—
Production tax credits	(6.0	)	(6.4	)	(6.1	)	(7.1	)	(6.4	)	(6.5	)
Effect of rate-making on property-related differences	(5.9	)	(7.0	)	(12.5	)	(16.6	)	(0.9	)	(0.6	)
Other items, net	2.8		4.3		2.6		4.9		4.7		4.4
Overall income tax rate	17.5	%	15.7	%	—	%	(9.0	%)	32.4	%	32.3	%

Summary Of Tax Credit Carryforwards

At June 30, 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		$769		$264		$349		$117		$311		$109
State net operating losses	2018	747		39		20		1		38		2
Federal tax credits	2022	258		254		93		90		105		105
					$557				$208				$216

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 June 30	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	(7.9	)	(10.6	)	(16.6	)	(25.3	)	—		—
Production tax credits	(5.7	)	(6.5	)	(5.3	)	(7.2	)	(6.3	)	(6.9	)
Effect of rate-making on property-related differences	(4.9	)	(8.4	)	(8.8	)	(22.3	)	(1.0	)	(0.7	)
Other items, net	0.7		4.1		(2.0	)	5.3		4.5		4.5
Overall income tax rate	17.2	%	13.6	%	2.3	%	(14.5	%)	32.2	%	31.9	%

	Alliant Energy				IPL				WPL
Six Months Ended June 30	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	(8.4	)	(10.2	)	(19.0	)	(25.2	)	—		—
Production tax credits	(6.0	)	(6.4	)	(6.1	)	(7.1	)	(6.4	)	(6.5	)
Effect of rate-making on property-related differences	(5.9	)	(7.0	)	(12.5	)	(16.6	)	(0.9	)	(0.6	)
Other items, net	2.8		4.3		2.6		4.9		4.7		4.4
Overall income tax rate	17.5	%	15.7	%	—	%	(9.0	%)	32.4	%	32.3	%

Summary Of Tax Credit Carryforwards

At June 30, 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		$769		$264		$349		$117		$311		$109
State net operating losses	2018	747		39		20		1		38		2
Federal tax credits	2022	258		254		93		90		105		105
					$557				$208				$216