Fair Value Measurements

3 Months Ended

Mar. 31, 2012

Fair Value Measurements

(9) FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments—The carrying amounts of Alliant Energy's, IPL's and WPL's current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and the related estimated fair values of other financial instruments at March 31, 2012 and Dec. 31, 2011 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
March 31, 2012
Assets:
Money market fund investments	$	21.3	$	21.3	$	21.3	$	21.3	$	—	$	—
Derivative assets (Note 10)		10.4		10.4		5.9		5.9		4.5		4.5
Deferred proceeds (sales of receivables) (Note 3)		32.9		32.9		32.9		32.9		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))		2,729.6		3,317.0		1,334.1		1,582.0		1,082.3		1,409.0
Cumulative preferred stock of subsidiaries		205.1		220.6		145.1		161.4		60.0		59.2
Derivative liabilities (Note 10)		83.2		83.2		38.1		38.1		45.1		45.1
Dec. 31, 2011
Assets:
Derivative assets (Note 10)		15.7		15.7		10.6		10.6		5.1		5.1
Deferred proceeds (sales of receivables) (Note 3)		53.7		53.7		53.7		53.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))		2,704.5		3,325.3		1,309.0		1,560.4		1,082.2		1,439.0
Cumulative preferred stock of subsidiaries		205.1		222.5		145.1		164.3		60.0		58.2
Derivative liabilities (Note 10)		78.0		78.0		33.6		33.6		44.4		44.4

Valuation Techniques -

Money market fund investments—As of March 31, 2012, money market fund investments were measured at fair value using quoted market prices on listed exchanges.

Derivative assets and derivative liabilities—Alliant Energy, IPL and WPL periodically use derivative instruments for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and currency exchange rates. Alliant Energy, IPL and WPL maintain risk policies that govern the use of derivative instruments. Alliant Energy's, IPL's and WPL's derivative instruments as of March 31, 2012 and Dec. 31, 2011 were not designated as hedging instruments. Alliant Energy's, IPL's and WPL's derivative instruments as of March 31, 2012 and Dec. 31, 2011 included electric physical forward purchase contracts and swap contracts to mitigate pricing volatility for the electricity purchased to supply to IPL's and WPL's customers; electric physical forward sale contracts to offset long positions created by reductions in electricity demand forecasts; natural gas swap contracts to mitigate pricing volatility for the fuel used to supply to the natural gas-fired electric generating facilities they operate; natural gas options to mitigate price increases during periods of high demand or lack of supply; financial transmission rights (FTRs) acquired to manage transmission congestion costs; natural gas physical forward purchase and natural gas option contracts to mitigate pricing volatility for natural gas supplied to IPL's and WPL's retail customers; and natural gas physical purchase and sale contracts to optimize the value of natural gas pipeline capacity.

IPL's and WPL's swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations available through a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. IPL and WPL corroborated a portion of these indicative price quotations using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. IPL's and WPL's commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. IPL's and WPL's swap, option and physical forward commodity contracts were predominately at liquid trading points. IPL's and WPL's FTRs were measured at fair value each reporting date using monthly or annual auction shadow prices from relevant auctions. Refer to Note 10 for additional details of derivative assets and derivative liabilities.

Deferred proceeds (sales of receivables)—The fair value of IPL's deferred proceeds related to its sales of receivables program was calculated each reporting date using the cost approach valuation technique. The fair value represents the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash proceeds received from the receivables sold. Deferred proceeds represent IPL's maximum exposure to loss related to the receivables sold due to the short-term nature of the collection period. Refer to Note 3 for additional information regarding deferred proceeds.

Long-term debt (including current maturities)—For long-term debt instruments that are actively traded, the fair value was based upon quoted market prices for similar liabilities each reporting date. For long-term debt instruments that are not actively traded, the fair value was based on discounted cash flow methodology and utilizes assumptions of current market pricing curves at each reporting date. Refer to Note 7(b) for additional information regarding long-term debt.

Cumulative preferred stock of subsidiaries—The fair value of IPL's 8.375% cumulative preferred stock was based on its closing market price quoted by the New York Stock Exchange on each reporting date. The fair value of WPL's 4.50% cumulative preferred stock was based on the closing market price quoted by the NYSE Amex LLC on each reporting date. The fair value of WPL's remaining preferred stock was calculated based on the market yield of similar securities.

Valuation Hierarchy—Fair value measurement accounting establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and examples of each are as follows:

Level 1—Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. As of March 31, 2012, Level 1 items included money market fund investments, IPL's 8.375% cumulative preferred stock and WPL's 4.50% cumulative preferred stock.

Level 2—Pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. As of March 31, 2012 and Dec. 31, 2011, Level 2 items included IPL's and WPL's non-exchange traded commodity contracts. Level 2 items as of March 31, 2012 also included the remainder of WPL's cumulative preferred stock and substantially all of the long-term debt instruments.

Level 3—Pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. As of March 31, 2012 and Dec. 31, 2011, Level 3 items included IPL's deferred proceeds, and IPL's and WPL's FTRs and certain commodity contracts.

The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. Items subject to fair value measurement disclosure requirements were as follows (Not Applicable (N/A); in millions):

	March 31, 2012								Dec. 31, 2011
Alliant Energy	Fair Value		Level 1		Level 2		Level 3		Fair Value		Level 1		Level 2		Level 3
Assets:
Money market fund investments	$	21.3		21.3	$	—	$	—	$	—	$	—	$	—	$	—
Derivatives—commodity contracts		10.4		—		4.9		5.5		15.7		—		3.4		12.3
Deferred proceeds		32.9		—		—		32.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)		3,317.0		—		3,316.5		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries		220.6		171.1		49.5		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		83.2		—		62.6		20.6		78.0		—		64.8		13.2

	March 31, 2012								Dec. 31, 2011
IPL	Fair Value		Level 1		Level 2		Level 3		Fair Value		Level 1		Level 2		Level 3
Assets:
Money market fund investments	$	21.3	$	21.3	$	—	$	—	$	—	$	—	$	—	$	—
Derivatives—commodity contracts		5.9		—		2.3		3.6		10.6		—		1.3		9.3
Deferred proceeds		32.9		—		—		32.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt		1,582.0		—		1,582.0		—		N/A		N/A		N/A		N/A
Cumulative preferred stock		161.4		161.4		—		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		38.1		—		23.1		15.0		33.6		—		28.6		5.0

	March 31, 2012								Dec. 31, 2011
WPL	Fair Value		Level 1		Level 2		Level 3		Fair Value		Level 1		Level 2		Level 3
Assets:
Derivatives—commodity contracts	$	4.5	$	—	$	2.6	$	1.9	$	5.1	$	—	$	2.1	$	3.0
Capitalization and liabilities:
Long-term debt		1,409.0		—		1,409.0		—		N/A		N/A		N/A		N/A
Cumulative preferred stock		59.2		9.7		49.5		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		45.1		—		39.5		5.6		44.4		—		36.2		8.2

In accordance with IPL's and WPL's fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recovered from customers in the future after any losses are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities resulted in comparable changes to regulatory assets and the changes in the fair value of derivative assets resulted in comparable changes to regulatory liabilities on the Condensed Consolidated Balance Sheets.

The significant unobservable inputs (Level 3 inputs) used in the fair value measurement of IPL's and WPL's commodity contracts are forecasted electricity and natural gas prices, and the expected volatility of such prices. Significant changes in any of those inputs would result in a significantly lower or higher fair value measurement. Information for fair value measurements using significant unobservable inputs (Level 3 inputs) for the three months ended March 31 was as follows (in millions):

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
Alliant Energy	2012			2011			2012		2011			2012			2011
Beginning balance, Jan. 1	($	0.9	)	$	2.8		$	—	$	4.7		$	53.7		$	152.9
Total losses (realized/unrealized) included in changes in net assets (a)		(12.5	)		(0.5	)		—		—			—			—
Transfers into Level 3 (b)		(3.8	)		—			—		—			—			—
Transfers out of Level 3 (c)		5.3			—			—		—			—			—
Settlements (d)		(3.2	)		(3.4	)		—		(2.6	)		(20.8	)		(23.1	)
Ending balance, March 31	($	15.1	)	($	1.1	)	$	—	$	2.1		$	32.9		$	129.8
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	12.5	)	($	0.5	)	$	—	$	—		$	—		$	—

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
IPL	2012			2011			2012		2011			2012			2011
Beginning balance, Jan. 1	$	4.3		$	4.3		$	—	$	4.8		$	53.7		$	152.9
Total losses (realized/unrealized) included in changes in net assets (a)		(10.8	)		(0.2	)		—		—			—			—
Transfers into Level 3 (b)		(2.7	)		—			—		—			—			—
Transfers out of Level 3 (c)		0.1			—			—		—			—			—
Settlements (d)		(2.3	)		(2.7	)		—		(2.7	)		(20.8	)		(23.1	)
Ending balance, March 31	($	11.4	)	$	1.4		$	—	$	2.1		$	32.9		$	129.8
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	10.8	)	($	0.2	)	$	—	$	—		$	—		$	—

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts
WPL	2012			2011			2012		2011
Beginning balance, Jan. 1	($	5.2	)	($	1.5	)	$	—	($	0.1	)
Total losses (realized/unrealized) included in changes in net assets (a)		(1.7	)		(0.3	)		—		—
Transfers into Level 3 (b)		(1.1	)		—			—		—
Transfers out of Level 3 (c)		5.2			—			—		—
Settlements		(0.9	)		(0.7	)		—		0.1
Ending balance, March 31	($	3.7	)	($	2.5	)	$	—	$	—
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	1.7	)	($	0.3	)	$	—	$	—

(a) Losses related to derivative assets and derivative liabilities are recorded in "Regulatory assets" and "Regulatory liabilities" on the Condensed Consolidated Balance Sheets.

(b) Markets for similar assets and liabilities were not active and observable market inputs were not available for transfers into Level 3. The transfers were valued as of the beginning of the period.

(c) Observable market inputs became available for certain commodity contracts previously classified as Level 3 for transfers out of Level 3. The transfers were valued as of the beginning of the period.

(d) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash proceeds received from the receivables sold.

Electric and Natural Gas Commodity Contracts —As of March 31, 2012, the fair values of Alliant Energy's, IPL's and WPL's electric and natural gas commodity contracts classified as Level 3, excluding FTRs, were recognized as net derivative liabilities of $18.4 million, $14.3 million and $4.1 million, respectively. These commodity contracts were valued using a market approach technique that utilizes significant observable inputs to estimate forward commodity prices. Forward electric prices are estimated using market information obtained from counterparties and brokers, including bids, offers, historical transactions (including historical price differences between locations with both observable and unobservable prices) and executed trades. Forward natural gas prices are estimated using the most recent quoted observable inputs applied to future months (including historical price differences between locations with both observable and unobservable prices). Observable inputs are obtained from compiled third-party pricing data sources and include bids, offers, historical transactions and executed trades. Forward electric price commodity curves that extend beyond currently available observable inputs utilize market prices for the most recent period for which observable inputs are available. Observable inputs include bids, offers, historical transactions and executed trades.

FTRs—As of March 31, 2012, Alliant Energy's, IPL's and WPL's FTRs classified as Level 3 were recognized as net derivative assets of $3.3 million, $2.9 million and $0.4 million, respectively. These FTRs were measured at fair value using monthly or annual auction shadow prices for identical or similar instruments from relevant closed auctions.

IPL [Member]

Fair Value Measurements

(9) FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments—The carrying amounts of Alliant Energy's, IPL's and WPL's current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and the related estimated fair values of other financial instruments at March 31, 2012 and Dec. 31, 2011 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying		Fair		Carrying		Fair		Carrying		Fair
	Amount		Value		Amount		Value		Amount		Value
March 31, 2012
Assets:
Money market fund investments	$	21.3	$	21.3	$	21.3	$	21.3	$	—	$	—
Derivative assets (Note 10)		10.4		10.4		5.9		5.9		4.5		4.5
Deferred proceeds (sales of receivables) (Note 3)		32.9		32.9		32.9		32.9		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))		2,729.6		3,317.0		1,334.1		1,582.0		1,082.3		1,409.0
Cumulative preferred stock of subsidiaries		205.1		220.6		145.1		161.4		60.0		59.2
Derivative liabilities (Note 10)		83.2		83.2		38.1		38.1		45.1		45.1
Dec. 31, 2011
Assets:
Derivative assets (Note 10)		15.7		15.7		10.6		10.6		5.1		5.1
Deferred proceeds (sales of receivables) (Note 3)		53.7		53.7		53.7		53.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))		2,704.5		3,325.3		1,309.0		1,560.4		1,082.2		1,439.0
Cumulative preferred stock of subsidiaries		205.1		222.5		145.1		164.3		60.0		58.2
Derivative liabilities (Note 10)		78.0		78.0		33.6		33.6		44.4		44.4

Valuation Techniques -

Money market fund investments—As of March 31, 2012, money market fund investments were measured at fair value using quoted market prices on listed exchanges.

Derivative assets and derivative liabilities—Alliant Energy, IPL and WPL periodically use derivative instruments for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and currency exchange rates. Alliant Energy, IPL and WPL maintain risk policies that govern the use of derivative instruments. Alliant Energy's, IPL's and WPL's derivative instruments as of March 31, 2012 and Dec. 31, 2011 were not designated as hedging instruments. Alliant Energy's, IPL's and WPL's derivative instruments as of March 31, 2012 and Dec. 31, 2011 included electric physical forward purchase contracts and swap contracts to mitigate pricing volatility for the electricity purchased to supply to IPL's and WPL's customers; electric physical forward sale contracts to offset long positions created by reductions in electricity demand forecasts; natural gas swap contracts to mitigate pricing volatility for the fuel used to supply to the natural gas-fired electric generating facilities they operate; natural gas options to mitigate price increases during periods of high demand or lack of supply; financial transmission rights (FTRs) acquired to manage transmission congestion costs; natural gas physical forward purchase and natural gas option contracts to mitigate pricing volatility for natural gas supplied to IPL's and WPL's retail customers; and natural gas physical purchase and sale contracts to optimize the value of natural gas pipeline capacity.

IPL's and WPL's swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations available through a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. IPL and WPL corroborated a portion of these indicative price quotations using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. IPL's and WPL's commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. IPL's and WPL's swap, option and physical forward commodity contracts were predominately at liquid trading points. IPL's and WPL's FTRs were measured at fair value each reporting date using monthly or annual auction shadow prices from relevant auctions. Refer to Note 10 for additional details of derivative assets and derivative liabilities.

Deferred proceeds (sales of receivables)—The fair value of IPL's deferred proceeds related to its sales of receivables program was calculated each reporting date using the cost approach valuation technique. The fair value represents the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash proceeds received from the receivables sold. Deferred proceeds represent IPL's maximum exposure to loss related to the receivables sold due to the short-term nature of the collection period. Refer to Note 3 for additional information regarding deferred proceeds.

Long-term debt (including current maturities)—For long-term debt instruments that are actively traded, the fair value was based upon quoted market prices for similar liabilities each reporting date. For long-term debt instruments that are not actively traded, the fair value was based on discounted cash flow methodology and utilizes assumptions of current market pricing curves at each reporting date. Refer to Note 7(b) for additional information regarding long-term debt.

Cumulative preferred stock of subsidiaries—The fair value of IPL's 8.375% cumulative preferred stock was based on its closing market price quoted by the New York Stock Exchange on each reporting date. The fair value of WPL's 4.50% cumulative preferred stock was based on the closing market price quoted by the NYSE Amex LLC on each reporting date. The fair value of WPL's remaining preferred stock was calculated based on the market yield of similar securities.

Valuation Hierarchy—Fair value measurement accounting establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and examples of each are as follows:

Level 1—Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. As of March 31, 2012, Level 1 items included money market fund investments, IPL's 8.375% cumulative preferred stock and WPL's 4.50% cumulative preferred stock.

Level 2—Pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. As of March 31, 2012 and Dec. 31, 2011, Level 2 items included IPL's and WPL's non-exchange traded commodity contracts. Level 2 items as of March 31, 2012 also included the remainder of WPL's cumulative preferred stock and substantially all of the long-term debt instruments.

Level 3—Pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. As of March 31, 2012 and Dec. 31, 2011, Level 3 items included IPL's deferred proceeds, and IPL's and WPL's FTRs and certain commodity contracts.

The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. Items subject to fair value measurement disclosure requirements were as follows (Not Applicable (N/A); in millions):

	March 31, 2012								Dec. 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
Alliant Energy	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments	$	21.3		21.3	$	—	$	—	$	—	$	—	$	—	$	—
Derivatives—commodity contracts		10.4		—		4.9		5.5		15.7		—		3.4		12.3
Deferred proceeds		32.9		—		—		32.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)		3,317.0		—		3,316.5		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries		220.6		171.1		49.5		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		83.2		—		62.6		20.6		78.0		—		64.8		13.2

	March 31, 2012								Dec. 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
IPL	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments	$	21.3	$	21.3	$	—	$	—	$	—	$	—	$	—	$	—
Derivatives—commodity contracts		5.9		—		2.3		3.6		10.6		—		1.3		9.3
Deferred proceeds		32.9		—		—		32.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt		1,582.0		—		1,582.0		—		N/A		N/A		N/A		N/A
Cumulative preferred stock		161.4		161.4		—		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		38.1		—		23.1		15.0		33.6		—		28.6		5.0
	March 31, 2012								Dec. 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
WPL	Value		1		2		3		Value		1		2		3
Assets:
Derivatives—commodity contracts	$	4.5	$	—	$	2.6	$	1.9	$	5.1	$	—	$	2.1	$	3.0
Capitalization and liabilities:
Long-term debt		1,409.0		—		1,409.0		—		N/A		N/A		N/A		N/A
Cumulative preferred stock		59.2		9.7		49.5		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		45.1		—		39.5		5.6		44.4		—		36.2		8.2

In accordance with IPL's and WPL's fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recovered from customers in the future after any losses are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities resulted in comparable changes to regulatory assets and the changes in the fair value of derivative assets resulted in comparable changes to regulatory liabilities on the Condensed Consolidated Balance Sheets.

The significant unobservable inputs (Level 3 inputs) used in the fair value measurement of IPL's and WPL's commodity contracts are forecasted electricity and natural gas prices, and the expected volatility of such prices. Significant changes in any of those inputs would result in a significantly lower or higher fair value measurement. Information for fair value measurements using significant unobservable inputs (Level 3 inputs) for the three months ended March 31 was as follows (in millions):

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
Alliant Energy	2012			2011			2012		2011			2012			2011
Beginning balance, Jan. 1	($	0.9	)	$	2.8		$	—	$	4.7		$	53.7		$	152.9
Total losses (realized/unrealized) included in changes in net assets (a)		(12.5	)		(0.5	)		—		—			—			—
Transfers into Level 3 (b)		(3.8	)		—			—		—			—			—
Transfers out of Level 3 (c)		5.3			—			—		—			—			—
Settlements (d)		(3.2	)		(3.4	)		—		(2.6	)		(20.8	)		(23.1	)
Ending balance, March 31	($	15.1	)	($	1.1	)	$	—	$	2.1		$	32.9		$	129.8
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	12.5	)	($	0.5	)	$	—	$	—		$	—		$	—

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
IPL	2012			2011			2012		2011			2012			2011
Beginning balance, Jan. 1	$	4.3		$	4.3		$	—	$	4.8		$	53.7		$	152.9
Total losses (realized/unrealized) included in changes in net assets (a)		(10.8	)		(0.2	)		—		—			—			—
Transfers into Level 3 (b)		(2.7	)		—			—		—			—			—
Transfers out of Level 3 (c)		0.1			—			—		—			—			—
Settlements (d)		(2.3	)		(2.7	)		—		(2.7	)		(20.8	)		(23.1	)
Ending balance, March 31	($	11.4	)	$	1.4		$	—	$	2.1		$	32.9		$	129.8
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	10.8	)	($	0.2	)	$	—	$	—		$	—		$	—

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts
WPL	2012			2011			2012		2011
Beginning balance, Jan. 1	($	5.2	)	($	1.5	)	$	—	($	0.1	)
Total losses (realized/unrealized) included in changes in net assets (a)		(1.7	)		(0.3	)		—		—
Transfers into Level 3 (b)		(1.1	)		—			—		—
Transfers out of Level 3 (c)		5.2			—			—		—
Settlements		(0.9	)		(0.7	)		—		0.1
Ending balance, March 31	($	3.7	)	($	2.5	)	$	—	$	—
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	1.7	)	($	0.3	)	$	—	$	—

(a) Losses related to derivative assets and derivative liabilities are recorded in "Regulatory assets" and "Regulatory liabilities" on the Condensed Consolidated Balance Sheets.

(b) Markets for similar assets and liabilities were not active and observable market inputs were not available for transfers into Level 3. The transfers were valued as of the beginning of the period.

(c) Observable market inputs became available for certain commodity contracts previously classified as Level 3 for transfers out of Level 3. The transfers were valued as of the beginning of the period.

(d) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash proceeds received from the receivables sold.

Electric and Natural Gas Commodity Contracts —As of March 31, 2012, the fair values of Alliant Energy's, IPL's and WPL's electric and natural gas commodity contracts classified as Level 3, excluding FTRs, were recognized as net derivative liabilities of $18.4 million, $14.3 million and $4.1 million, respectively. These commodity contracts were valued using a market approach technique that utilizes significant observable inputs to estimate forward commodity prices. Forward electric prices are estimated using market information obtained from counterparties and brokers, including bids, offers, historical transactions (including historical price differences between locations with both observable and unobservable prices) and executed trades. Forward natural gas prices are estimated using the most recent quoted observable inputs applied to future months (including historical price differences between locations with both observable and unobservable prices). Observable inputs are obtained from compiled third-party pricing data sources and include bids, offers, historical transactions and executed trades. Forward electric price commodity curves that extend beyond currently available observable inputs utilize market prices for the most recent period for which observable inputs are available. Observable inputs include bids, offers, historical transactions and executed trades.

FTRs—As of March 31, 2012, Alliant Energy's, IPL's and WPL's FTRs classified as Level 3 were recognized as net derivative assets of $3.3 million, $2.9 million and $0.4 million, respectively. These FTRs were measured at fair value using monthly or annual auction shadow prices for identical or similar instruments from relevant closed auctions.

WPL [Member]

Fair Value Measurements

(9) FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments—The carrying amounts of Alliant Energy's, IPL's and WPL's current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and the related estimated fair values of other financial instruments at March 31, 2012 and Dec. 31, 2011 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying		Fair		Carrying		Fair		Carrying		Fair
	Amount		Value		Amount		Value		Amount		Value
March 31, 2012
Assets:
Money market fund investments	$	21.3	$	21.3	$	21.3	$	21.3	$	—	$	—
Derivative assets (Note 10)		10.4		10.4		5.9		5.9		4.5		4.5
Deferred proceeds (sales of receivables) (Note 3)		32.9		32.9		32.9		32.9		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))		2,729.6		3,317.0		1,334.1		1,582.0		1,082.3		1,409.0
Cumulative preferred stock of subsidiaries		205.1		220.6		145.1		161.4		60.0		59.2
Derivative liabilities (Note 10)		83.2		83.2		38.1		38.1		45.1		45.1
Dec. 31, 2011
Assets:
Derivative assets (Note 10)		15.7		15.7		10.6		10.6		5.1		5.1
Deferred proceeds (sales of receivables) (Note 3)		53.7		53.7		53.7		53.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))		2,704.5		3,325.3		1,309.0		1,560.4		1,082.2		1,439.0
Cumulative preferred stock of subsidiaries		205.1		222.5		145.1		164.3		60.0		58.2
Derivative liabilities (Note 10)		78.0		78.0		33.6		33.6		44.4		44.4

Valuation Techniques -

Money market fund investments—As of March 31, 2012, money market fund investments were measured at fair value using quoted market prices on listed exchanges.

Derivative assets and derivative liabilities—Alliant Energy, IPL and WPL periodically use derivative instruments for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and currency exchange rates. Alliant Energy, IPL and WPL maintain risk policies that govern the use of derivative instruments. Alliant Energy's, IPL's and WPL's derivative instruments as of March 31, 2012 and Dec. 31, 2011 were not designated as hedging instruments. Alliant Energy's, IPL's and WPL's derivative instruments as of March 31, 2012 and Dec. 31, 2011 included electric physical forward purchase contracts and swap contracts to mitigate pricing volatility for the electricity purchased to supply to IPL's and WPL's customers; electric physical forward sale contracts to offset long positions created by reductions in electricity demand forecasts; natural gas swap contracts to mitigate pricing volatility for the fuel used to supply to the natural gas-fired electric generating facilities they operate; natural gas options to mitigate price increases during periods of high demand or lack of supply; financial transmission rights (FTRs) acquired to manage transmission congestion costs; natural gas physical forward purchase and natural gas option contracts to mitigate pricing volatility for natural gas supplied to IPL's and WPL's retail customers; and natural gas physical purchase and sale contracts to optimize the value of natural gas pipeline capacity.

IPL's and WPL's swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations available through a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. IPL and WPL corroborated a portion of these indicative price quotations using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. IPL's and WPL's commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. IPL's and WPL's swap, option and physical forward commodity contracts were predominately at liquid trading points. IPL's and WPL's FTRs were measured at fair value each reporting date using monthly or annual auction shadow prices from relevant auctions. Refer to Note 10 for additional details of derivative assets and derivative liabilities.

Deferred proceeds (sales of receivables)—The fair value of IPL's deferred proceeds related to its sales of receivables program was calculated each reporting date using the cost approach valuation technique. The fair value represents the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash proceeds received from the receivables sold. Deferred proceeds represent IPL's maximum exposure to loss related to the receivables sold due to the short-term nature of the collection period. Refer to Note 3 for additional information regarding deferred proceeds.

Long-term debt (including current maturities)—For long-term debt instruments that are actively traded, the fair value was based upon quoted market prices for similar liabilities each reporting date. For long-term debt instruments that are not actively traded, the fair value was based on discounted cash flow methodology and utilizes assumptions of current market pricing curves at each reporting date. Refer to Note 7(b) for additional information regarding long-term debt.

Cumulative preferred stock of subsidiaries—The fair value of IPL's 8.375% cumulative preferred stock was based on its closing market price quoted by the New York Stock Exchange on each reporting date. The fair value of WPL's 4.50% cumulative preferred stock was based on the closing market price quoted by the NYSE Amex LLC on each reporting date. The fair value of WPL's remaining preferred stock was calculated based on the market yield of similar securities.

Valuation Hierarchy—Fair value measurement accounting establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and examples of each are as follows:

Level 1—Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. As of March 31, 2012, Level 1 items included money market fund investments, IPL's 8.375% cumulative preferred stock and WPL's 4.50% cumulative preferred stock.

Level 2—Pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. As of March 31, 2012 and Dec. 31, 2011, Level 2 items included IPL's and WPL's non-exchange traded commodity contracts. Level 2 items as of March 31, 2012 also included the remainder of WPL's cumulative preferred stock and substantially all of the long-term debt instruments.

Level 3—Pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. As of March 31, 2012 and Dec. 31, 2011, Level 3 items included IPL's deferred proceeds, and IPL's and WPL's FTRs and certain commodity contracts.

The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. Items subject to fair value measurement disclosure requirements were as follows (Not Applicable (N/A); in millions):

	March 31, 2012								Dec. 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
Alliant Energy	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments	$	21.3		21.3	$	—	$	—	$	—	$	—	$	—	$	—
Derivatives—commodity contracts		10.4		—		4.9		5.5		15.7		—		3.4		12.3
Deferred proceeds		32.9		—		—		32.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)		3,317.0		—		3,316.5		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries		220.6		171.1		49.5		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		83.2		—		62.6		20.6		78.0		—		64.8		13.2

	March 31, 2012								Dec. 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
IPL	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments	$	21.3	$	21.3	$	—	$	—	$	—	$	—	$	—	$	—
Derivatives—commodity contracts		5.9		—		2.3		3.6		10.6		—		1.3		9.3
Deferred proceeds		32.9		—		—		32.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt		1,582.0		—		1,582.0		—		N/A		N/A		N/A		N/A
Cumulative preferred stock		161.4		161.4		—		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		38.1		—		23.1		15.0		33.6		—		28.6		5.0
	March 31, 2012								Dec. 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
WPL	Value		1		2		3		Value		1		2		3
Assets:
Derivatives—commodity contracts	$	4.5	$	—	$	2.6	$	1.9	$	5.1	$	—	$	2.1	$	3.0
Capitalization and liabilities:
Long-term debt		1,409.0		—		1,409.0		—		N/A		N/A		N/A		N/A
Cumulative preferred stock		59.2		9.7		49.5		—		N/A		N/A		N/A		N/A
Derivatives—commodity contracts		45.1		—		39.5		5.6		44.4		—		36.2		8.2

In accordance with IPL's and WPL's fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recovered from customers in the future after any losses are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities resulted in comparable changes to regulatory assets and the changes in the fair value of derivative assets resulted in comparable changes to regulatory liabilities on the Condensed Consolidated Balance Sheets.

The significant unobservable inputs (Level 3 inputs) used in the fair value measurement of IPL's and WPL's commodity contracts are forecasted electricity and natural gas prices, and the expected volatility of such prices. Significant changes in any of those inputs would result in a significantly lower or higher fair value measurement. Information for fair value measurements using significant unobservable inputs (Level 3 inputs) for the three months ended March 31 was as follows (in millions):

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
Alliant Energy	2012			2011			2012		2011			2012			2011
Beginning balance, Jan. 1	($	0.9	)	$	2.8		$	—	$	4.7		$	53.7		$	152.9
Total losses (realized/unrealized) included in changes in net assets (a)		(12.5	)		(0.5	)		—		—			—			—
Transfers into Level 3 (b)		(3.8	)		—			—		—			—			—
Transfers out of Level 3 (c)		5.3			—			—		—			—			—
Settlements (d)		(3.2	)		(3.4	)		—		(2.6	)		(20.8	)		(23.1	)
Ending balance, March 31	($	15.1	)	($	1.1	)	$	—	$	2.1		$	32.9		$	129.8
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	12.5	)	($	0.5	)	$	—	$	—		$	—		$	—

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
IPL	2012			2011			2012		2011			2012			2011
Beginning balance, Jan. 1	$	4.3		$	4.3		$	—	$	4.8		$	53.7		$	152.9
Total losses (realized/unrealized) included in changes in net assets (a)		(10.8	)		(0.2	)		—		—			—			—
Transfers into Level 3 (b)		(2.7	)		—			—		—			—			—
Transfers out of Level 3 (c)		0.1			—			—		—			—			—
Settlements (d)		(2.3	)		(2.7	)		—		(2.7	)		(20.8	)		(23.1	)
Ending balance, March 31	($	11.4	)	$	1.4		$	—	$	2.1		$	32.9		$	129.8
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	10.8	)	($	0.2	)	$	—	$	—		$	—		$	—

	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts
WPL	2012			2011			2012		2011
Beginning balance, Jan. 1	($	5.2	)	($	1.5	)	$	—	($	0.1	)
Total losses (realized/unrealized) included in changes in net assets (a)		(1.7	)		(0.3	)		—		—
Transfers into Level 3 (b)		(1.1	)		—			—		—
Transfers out of Level 3 (c)		5.2			—			—		—
Settlements		(0.9	)		(0.7	)		—		0.1
Ending balance, March 31	($	3.7	)	($	2.5	)	$	—	$	—
The amount of total losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 (a)	($	1.7	)	($	0.3	)	$	—	$	—

(a) Losses related to derivative assets and derivative liabilities are recorded in "Regulatory assets" and "Regulatory liabilities" on the Condensed Consolidated Balance Sheets.

(b) Markets for similar assets and liabilities were not active and observable market inputs were not available for transfers into Level 3. The transfers were valued as of the beginning of the period.

(c) Observable market inputs became available for certain commodity contracts previously classified as Level 3 for transfers out of Level 3. The transfers were valued as of the beginning of the period.

(d) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for doubtful accounts associated with the receivables sold and cash proceeds received from the receivables sold.

Electric and Natural Gas Commodity Contracts —As of March 31, 2012, the fair values of Alliant Energy's, IPL's and WPL's electric and natural gas commodity contracts classified as Level 3, excluding FTRs, were recognized as net derivative liabilities of $18.4 million, $14.3 million and $4.1 million, respectively. These commodity contracts were valued using a market approach technique that utilizes significant observable inputs to estimate forward commodity prices. Forward electric prices are estimated using market information obtained from counterparties and brokers, including bids, offers, historical transactions (including historical price differences between locations with both observable and unobservable prices) and executed trades. Forward natural gas prices are estimated using the most recent quoted observable inputs applied to future months (including historical price differences between locations with both observable and unobservable prices). Observable inputs are obtained from compiled third-party pricing data sources and include bids, offers, historical transactions and executed trades. Forward electric price commodity curves that extend beyond currently available observable inputs utilize market prices for the most recent period for which observable inputs are available. Observable inputs include bids, offers, historical transactions and executed trades.

FTRs—As of March 31, 2012, Alliant Energy's, IPL's and WPL's FTRs classified as Level 3 were recognized as net derivative assets of $3.3 million, $2.9 million and $0.4 million, respectively. These FTRs were measured at fair value using monthly or annual auction shadow prices for identical or similar instruments from relevant closed auctions.