Income Taxes (Tables)

3 Months Ended

Mar. 31, 2015

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 before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(9.9	)	(11.9	)	(25.2	)	(31.2	)	—		—
Production tax credits	(6.2	)	(6.7	)	(7.3	)	(8.3	)	(6.0	)	(6.4	)
Effect of rate-making on property-related differences	(6.1	)	(5.3	)	(14.6	)	(12.4	)	(0.6	)	(1.0	)
Other items, net	4.3		4.6		4.4		4.7		4.6		4.8
Overall income tax rate	17.1	%	15.7	%	(7.7	%)	(12.2	%)	33.0	%	32.4	%

Production Tax Credits (Net Of State Tax Impacts)

For the three months ended March 31, details regarding production tax credits (net of state tax impacts) related to various wind projects are as follows (dollars in millions):

	End of Production	Nameplate
	Tax Credit Generation	Capacity in MW	2015		2014
Cedar Ridge (WPL)	December 2018	68		$1.2		$1.2
Bent Tree - Phase I (WPL)	February 2021	201	3.9		4.2
Subtotal (WPL)			5.1		5.4
Whispering Willow - East (IPL)	December 2019	200	4.3		4.6
				$9.4		$10.0

Summary Of Tax Credit Carryforwards

At March 31, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

Alliant Energy	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$894		$306	2029
State net operating losses	853		44		2018
Federal tax credits	214		210		2022
				$560

IPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$424		$145	2029
State net operating losses	260		13		2018
Federal tax credits	73		72		2022
				$230

WPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$355		$122	2029
State net operating losses	166		8		2018
Federal tax credits	82		80		2022
				$210

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 before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(9.9	)	(11.9	)	(25.2	)	(31.2	)	—		—
Production tax credits	(6.2	)	(6.7	)	(7.3	)	(8.3	)	(6.0	)	(6.4	)
Effect of rate-making on property-related differences	(6.1	)	(5.3	)	(14.6	)	(12.4	)	(0.6	)	(1.0	)
Other items, net	4.3		4.6		4.4		4.7		4.6		4.8
Overall income tax rate	17.1	%	15.7	%	(7.7	%)	(12.2	%)	33.0	%	32.4	%

Production Tax Credits (Net Of State Tax Impacts)

For the three months ended March 31, details regarding production tax credits (net of state tax impacts) related to various wind projects are as follows (dollars in millions):

	End of Production	Nameplate
	Tax Credit Generation	Capacity in MW	2015		2014
Cedar Ridge (WPL)	December 2018	68		$1.2		$1.2
Bent Tree - Phase I (WPL)	February 2021	201	3.9		4.2
Subtotal (WPL)			5.1		5.4
Whispering Willow - East (IPL)	December 2019	200	4.3		4.6
				$9.4		$10.0

Summary Of Tax Credit Carryforwards

At March 31, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

Alliant Energy	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$894		$306	2029
State net operating losses	853		44		2018
Federal tax credits	214		210		2022
				$560

IPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$424		$145	2029
State net operating losses	260		13		2018
Federal tax credits	73		72		2022
				$230

WPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$355		$122	2029
State net operating losses	166		8		2018
Federal tax credits	82		80		2022
				$210

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 before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(9.9	)	(11.9	)	(25.2	)	(31.2	)	—		—
Production tax credits	(6.2	)	(6.7	)	(7.3	)	(8.3	)	(6.0	)	(6.4	)
Effect of rate-making on property-related differences	(6.1	)	(5.3	)	(14.6	)	(12.4	)	(0.6	)	(1.0	)
Other items, net	4.3		4.6		4.4		4.7		4.6		4.8
Overall income tax rate	17.1	%	15.7	%	(7.7	%)	(12.2	%)	33.0	%	32.4	%

Production Tax Credits (Net Of State Tax Impacts)

For the three months ended March 31, details regarding production tax credits (net of state tax impacts) related to various wind projects are as follows (dollars in millions):

	End of Production	Nameplate
	Tax Credit Generation	Capacity in MW	2015		2014
Cedar Ridge (WPL)	December 2018	68		$1.2		$1.2
Bent Tree - Phase I (WPL)	February 2021	201	3.9		4.2
Subtotal (WPL)			5.1		5.4
Whispering Willow - East (IPL)	December 2019	200	4.3		4.6
				$9.4		$10.0

Summary Of Tax Credit Carryforwards

At March 31, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

Alliant Energy	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$894		$306	2029
State net operating losses	853		44		2018
Federal tax credits	214		210		2022
				$560

IPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$424		$145	2029
State net operating losses	260		13		2018
Federal tax credits	73		72		2022
				$230

WPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$355		$122	2029
State net operating losses	166		8		2018
Federal tax credits	82		80		2022
				$210