Fair Value Measurements

6 Months Ended

Jun. 30, 2016

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Valuation Hierarchy - At each reporting date, Level 1 items included IPL’s 5.1% cumulative preferred stock, Level 2 items included certain non-exchange traded commodity contracts and substantially all of the long-term debt instruments, and Level 3 items included FTRs, certain non-exchange traded commodity contracts and IPL’s deferred proceeds.

Valuation Techniques -

Derivative assets and derivative liabilities - Derivative instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Risk policies are maintained that govern the use of such derivative instruments. Derivative instruments were not designated as hedging instruments and included the following:

Risk management purpose	Type of instrument
Mitigate pricing volatility for:
Electricity purchased to supply customers	Electric swap and physical forward contracts (IPL and WPL)
Fuel used to supply natural gas-fired EGUs	Natural gas swap and physical forward contracts (IPL and WPL)
Natural gas supplied to retail customers	Natural gas options and physical forward contracts (IPL and WPL)
	Natural gas swap contracts (IPL)
Fuel used at coal-fired EGUs	Coal physical forward contracts (IPL and WPL)
Optimize the value of natural gas pipeline capacity	Natural gas physical forward contracts (IPL and WPL)
	Natural gas swap contracts (IPL)
Manage transmission congestion costs	FTRs (IPL and WPL)
Manage rail transportation costs	Diesel fuel swap contracts (WPL)

Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications 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. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. 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. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using monthly or annual auction shadow prices from relevant auctions and were categorized as Level 3. Refer to Note 12 for additional details of derivative assets and derivative liabilities.

The fair value measurements of Level 3 derivative instruments include observable and unobservable inputs. The observable inputs are obtained from third-party pricing sources, counterparties and brokers and include bids, offers, historical transactions (including historical price differences between locations with both observable and unobservable prices) and executed trades. The significant unobservable inputs used in the fair value measurement of commodity contracts are forecasted electricity, natural gas and coal 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.

Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable 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 amounts received from the receivables sold due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 4 for additional information regarding deferred proceeds.

Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on quoted market prices for similar liabilities at each reporting date or on a discounted cash flow methodology, which 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 - The fair value of IPL’s 5.1% cumulative preferred stock was based on its closing market price quoted by the New York Stock Exchange at each reporting date.

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$36.9		$—		$3.2		$33.7		$36.9		$18.4		$—		$2.5		$15.9		$18.4
Deferred proceeds	74.4		—		—		74.4		74.4		172.0		—		—		172.0		172.0
Liabilities and equity:
Derivatives	37.1		—		4.0		33.1		37.1		64.6		—		16.0		48.6		64.6
Long-term debt (including current maturities)	3,902.4		—		4,647.2		3.3		4,650.5		3,835.6		—		4,332.4		3.7		4,336.1
Cumulative preferred stock of IPL	200.0		218.3		—		—		218.3		200.0		206.6		—		—		206.6

IPL	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$28.1		$—		$1.8		$26.3		$28.1		$15.5		$—		$2.0		$13.5		$15.5
Deferred proceeds	74.4		—		—		74.4		74.4		172.0		—		—		172.0		172.0
Liabilities and equity:
Derivatives	9.8		—		1.8		8.0		9.8		23.4		—		8.0		15.4		23.4
Long-term debt (including current maturities)	1,924.8		—		2,271.3		—		2,271.3		1,856.9		—		2,092.7		—		2,092.7
Cumulative preferred stock	200.0		218.3		—		—		218.3		200.0		206.6		—		—		206.6

WPL	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$8.8		$—		$1.4		$7.4		$8.8		$2.9		$—		$0.5		$2.4		$2.9
Liabilities and equity:
Derivatives	27.3		—		2.2		25.1		27.3		41.2		—		8.0		33.2		41.2
Long-term debt (including current maturities)	1,534.6		—		1,923.5		—		1,923.5		1,533.9		—		1,793.0		—		1,793.0

Unrealized gains and losses from derivative instruments are generally recorded with offsets to regulatory assets or regulatory liabilities, based on fuel and natural gas cost recovery mechanisms, as well as other specific regulatory authorizations. 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.

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended June 30	2016			2015			2016			2015
Beginning balance, April 1		($65.9	)		($13.1	)		$154.2			$117.7
Total net gains (losses) included in changes in net assets (realized/unrealized)	44.6			(19.6		)	—			—
Transfers out of Level 3	0.4			1.0			—			—
Purchases	22.0			36.8			—			—
Sales	(0.1		)	(0.4		)	—			—
Settlements (a)	(0.4		)	(4.1		)	(79.8		)	(44.3		)
Ending balance, June 30		$0.6			$0.6			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$44.8			($17.7	)		$—			$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Six Months Ended June 30	2016			2015			2016			2015
Beginning balance, January 1		($32.7	)		$17.9			$172.0			$177.2
Total net gains (losses) included in changes in net assets (realized/unrealized)	13.1			(36.8		)	—			—
Transfers into Level 3	0.9			—			—			—
Transfers out of Level 3	0.4			0.6			—			—
Purchases	22.0			36.8			—			—
Sales	(0.7		)	(1.2		)	—			—
Settlements (a)	(2.4		)	(16.7		)	(97.6		)	(103.8		)
Ending balance, June 30		$0.6			$0.6			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$14.8			($33.9	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended June 30	2016			2015			2016			2015
Beginning balance, April 1		($13.1	)		($5.0	)		$154.2			$117.7
Total net gains (losses) included in changes in net assets (realized/unrealized)	12.9			(5.0		)	—			—
Transfers out of Level 3	(0.1		)	0.2			—			—
Purchases	20.6			33.1			—			—
Sales	(0.1		)	(0.4		)	—			—
Settlements (a)	(1.9		)	(4.6		)	(79.8		)	(44.3		)
Ending balance, June 30		$18.3			$18.3			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$12.8			($4.2	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Six Months Ended June 30	2016			2015			2016			2015
Beginning balance, January 1		($1.9	)		$19.4			$172.0			$177.2
Total net gains (losses) included in changes in net assets (realized/unrealized)	5.2			(17.4		)	—			—
Transfers into Level 3	0.5			—			—			—
Transfers out of Level 3	(0.1		)	—			—			—
Purchases	20.6			33.1			—			—
Sales	(0.7		)	(1.1		)	—			—
Settlements (a)	(5.3		)	(15.7		)	(97.6		)	(103.8		)
Ending balance, June 30		$18.3			$18.3			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$6.2			($14.3	)		$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended June 30	2016			2015
Beginning balance, April 1		($52.8	)		($8.1	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	31.7			(14.6		)
Transfers out of Level 3	0.5			0.8
Purchases	1.4			3.7
Settlements	1.5			0.5
Ending balance, June 30		($17.7	)		($17.7	)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$32.0			($13.5	)

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Six Months Ended June 30	2016			2015
Beginning balance, January 1		($30.8	)		($1.5	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	7.9			(19.4		)
Transfers into Level 3	0.4			—
Transfers out of Level 3	0.5			0.6
Purchases	1.4			3.7
Sales	—			(0.1		)
Settlements	2.9			(1.0		)
Ending balance, June 30		($17.7	)		($17.7	)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$8.6			($19.6	)

(a) 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.

Commodity Contracts - The fair value of electric, natural gas and coal commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):

	Alliant Energy					IPL					WPL
	Excluding FTRs			FTRs		Excluding FTRs			FTRs		Excluding FTRs			FTRs
June 30, 2016		($22.9	)		$23.5		($3.4	)		$21.7		($19.5	)		$1.8
December 31, 2015	(43.1		)	10.4		(12.3		)	10.4		(30.8		)	—

IPL [Member]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Valuation Hierarchy - At each reporting date, Level 1 items included IPL’s 5.1% cumulative preferred stock, Level 2 items included certain non-exchange traded commodity contracts and substantially all of the long-term debt instruments, and Level 3 items included FTRs, certain non-exchange traded commodity contracts and IPL’s deferred proceeds.

Valuation Techniques -

Derivative assets and derivative liabilities - Derivative instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Risk policies are maintained that govern the use of such derivative instruments. Derivative instruments were not designated as hedging instruments and included the following:

Risk management purpose	Type of instrument
Mitigate pricing volatility for:
Electricity purchased to supply customers	Electric swap and physical forward contracts (IPL and WPL)
Fuel used to supply natural gas-fired EGUs	Natural gas swap and physical forward contracts (IPL and WPL)
Natural gas supplied to retail customers	Natural gas options and physical forward contracts (IPL and WPL)
	Natural gas swap contracts (IPL)
Fuel used at coal-fired EGUs	Coal physical forward contracts (IPL and WPL)
Optimize the value of natural gas pipeline capacity	Natural gas physical forward contracts (IPL and WPL)
	Natural gas swap contracts (IPL)
Manage transmission congestion costs	FTRs (IPL and WPL)
Manage rail transportation costs	Diesel fuel swap contracts (WPL)

Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications 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. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. 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. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using monthly or annual auction shadow prices from relevant auctions and were categorized as Level 3. Refer to Note 12 for additional details of derivative assets and derivative liabilities.

The fair value measurements of Level 3 derivative instruments include observable and unobservable inputs. The observable inputs are obtained from third-party pricing sources, counterparties and brokers and include bids, offers, historical transactions (including historical price differences between locations with both observable and unobservable prices) and executed trades. The significant unobservable inputs used in the fair value measurement of commodity contracts are forecasted electricity, natural gas and coal 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.

Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable 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 amounts received from the receivables sold due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 4 for additional information regarding deferred proceeds.

Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on quoted market prices for similar liabilities at each reporting date or on a discounted cash flow methodology, which 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 - The fair value of IPL’s 5.1% cumulative preferred stock was based on its closing market price quoted by the New York Stock Exchange at each reporting date.

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$36.9		$—		$3.2		$33.7		$36.9		$18.4		$—		$2.5		$15.9		$18.4
Deferred proceeds	74.4		—		—		74.4		74.4		172.0		—		—		172.0		172.0
Liabilities and equity:
Derivatives	37.1		—		4.0		33.1		37.1		64.6		—		16.0		48.6		64.6
Long-term debt (including current maturities)	3,902.4		—		4,647.2		3.3		4,650.5		3,835.6		—		4,332.4		3.7		4,336.1
Cumulative preferred stock of IPL	200.0		218.3		—		—		218.3		200.0		206.6		—		—		206.6

IPL	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$28.1		$—		$1.8		$26.3		$28.1		$15.5		$—		$2.0		$13.5		$15.5
Deferred proceeds	74.4		—		—		74.4		74.4		172.0		—		—		172.0		172.0
Liabilities and equity:
Derivatives	9.8		—		1.8		8.0		9.8		23.4		—		8.0		15.4		23.4
Long-term debt (including current maturities)	1,924.8		—		2,271.3		—		2,271.3		1,856.9		—		2,092.7		—		2,092.7
Cumulative preferred stock	200.0		218.3		—		—		218.3		200.0		206.6		—		—		206.6

WPL	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$8.8		$—		$1.4		$7.4		$8.8		$2.9		$—		$0.5		$2.4		$2.9
Liabilities and equity:
Derivatives	27.3		—		2.2		25.1		27.3		41.2		—		8.0		33.2		41.2
Long-term debt (including current maturities)	1,534.6		—		1,923.5		—		1,923.5		1,533.9		—		1,793.0		—		1,793.0

Unrealized gains and losses from derivative instruments are generally recorded with offsets to regulatory assets or regulatory liabilities, based on fuel and natural gas cost recovery mechanisms, as well as other specific regulatory authorizations. 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.

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended June 30	2016			2015			2016			2015
Beginning balance, April 1		($65.9	)		($13.1	)		$154.2			$117.7
Total net gains (losses) included in changes in net assets (realized/unrealized)	44.6			(19.6		)	—			—
Transfers out of Level 3	0.4			1.0			—			—
Purchases	22.0			36.8			—			—
Sales	(0.1		)	(0.4		)	—			—
Settlements (a)	(0.4		)	(4.1		)	(79.8		)	(44.3		)
Ending balance, June 30		$0.6			$0.6			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$44.8			($17.7	)		$—			$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Six Months Ended June 30	2016			2015			2016			2015
Beginning balance, January 1		($32.7	)		$17.9			$172.0			$177.2
Total net gains (losses) included in changes in net assets (realized/unrealized)	13.1			(36.8		)	—			—
Transfers into Level 3	0.9			—			—			—
Transfers out of Level 3	0.4			0.6			—			—
Purchases	22.0			36.8			—			—
Sales	(0.7		)	(1.2		)	—			—
Settlements (a)	(2.4		)	(16.7		)	(97.6		)	(103.8		)
Ending balance, June 30		$0.6			$0.6			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$14.8			($33.9	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended June 30	2016			2015			2016			2015
Beginning balance, April 1		($13.1	)		($5.0	)		$154.2			$117.7
Total net gains (losses) included in changes in net assets (realized/unrealized)	12.9			(5.0		)	—			—
Transfers out of Level 3	(0.1		)	0.2			—			—
Purchases	20.6			33.1			—			—
Sales	(0.1		)	(0.4		)	—			—
Settlements (a)	(1.9		)	(4.6		)	(79.8		)	(44.3		)
Ending balance, June 30		$18.3			$18.3			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$12.8			($4.2	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Six Months Ended June 30	2016			2015			2016			2015
Beginning balance, January 1		($1.9	)		$19.4			$172.0			$177.2
Total net gains (losses) included in changes in net assets (realized/unrealized)	5.2			(17.4		)	—			—
Transfers into Level 3	0.5			—			—			—
Transfers out of Level 3	(0.1		)	—			—			—
Purchases	20.6			33.1			—			—
Sales	(0.7		)	(1.1		)	—			—
Settlements (a)	(5.3		)	(15.7		)	(97.6		)	(103.8		)
Ending balance, June 30		$18.3			$18.3			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$6.2			($14.3	)		$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended June 30	2016			2015
Beginning balance, April 1		($52.8	)		($8.1	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	31.7			(14.6		)
Transfers out of Level 3	0.5			0.8
Purchases	1.4			3.7
Settlements	1.5			0.5
Ending balance, June 30		($17.7	)		($17.7	)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$32.0			($13.5	)

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Six Months Ended June 30	2016			2015
Beginning balance, January 1		($30.8	)		($1.5	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	7.9			(19.4		)
Transfers into Level 3	0.4			—
Transfers out of Level 3	0.5			0.6
Purchases	1.4			3.7
Sales	—			(0.1		)
Settlements	2.9			(1.0		)
Ending balance, June 30		($17.7	)		($17.7	)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$8.6			($19.6	)

(a) 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.

Commodity Contracts - The fair value of electric, natural gas and coal commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):

	Alliant Energy					IPL					WPL
	Excluding FTRs			FTRs		Excluding FTRs			FTRs		Excluding FTRs			FTRs
June 30, 2016		($22.9	)		$23.5		($3.4	)		$21.7		($19.5	)		$1.8
December 31, 2015	(43.1		)	10.4		(12.3		)	10.4		(30.8		)	—

WPL [Member]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Valuation Hierarchy - At each reporting date, Level 1 items included IPL’s 5.1% cumulative preferred stock, Level 2 items included certain non-exchange traded commodity contracts and substantially all of the long-term debt instruments, and Level 3 items included FTRs, certain non-exchange traded commodity contracts and IPL’s deferred proceeds.

Valuation Techniques -

Derivative assets and derivative liabilities - Derivative instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Risk policies are maintained that govern the use of such derivative instruments. Derivative instruments were not designated as hedging instruments and included the following:

Risk management purpose	Type of instrument
Mitigate pricing volatility for:
Electricity purchased to supply customers	Electric swap and physical forward contracts (IPL and WPL)
Fuel used to supply natural gas-fired EGUs	Natural gas swap and physical forward contracts (IPL and WPL)
Natural gas supplied to retail customers	Natural gas options and physical forward contracts (IPL and WPL)
	Natural gas swap contracts (IPL)
Fuel used at coal-fired EGUs	Coal physical forward contracts (IPL and WPL)
Optimize the value of natural gas pipeline capacity	Natural gas physical forward contracts (IPL and WPL)
	Natural gas swap contracts (IPL)
Manage transmission congestion costs	FTRs (IPL and WPL)
Manage rail transportation costs	Diesel fuel swap contracts (WPL)

Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications 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. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. 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. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using monthly or annual auction shadow prices from relevant auctions and were categorized as Level 3. Refer to Note 12 for additional details of derivative assets and derivative liabilities.

The fair value measurements of Level 3 derivative instruments include observable and unobservable inputs. The observable inputs are obtained from third-party pricing sources, counterparties and brokers and include bids, offers, historical transactions (including historical price differences between locations with both observable and unobservable prices) and executed trades. The significant unobservable inputs used in the fair value measurement of commodity contracts are forecasted electricity, natural gas and coal 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.

Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable 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 amounts received from the receivables sold due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 4 for additional information regarding deferred proceeds.

Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on quoted market prices for similar liabilities at each reporting date or on a discounted cash flow methodology, which 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 - The fair value of IPL’s 5.1% cumulative preferred stock was based on its closing market price quoted by the New York Stock Exchange at each reporting date.

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant Energy	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$36.9		$—		$3.2		$33.7		$36.9		$18.4		$—		$2.5		$15.9		$18.4
Deferred proceeds	74.4		—		—		74.4		74.4		172.0		—		—		172.0		172.0
Liabilities and equity:
Derivatives	37.1		—		4.0		33.1		37.1		64.6		—		16.0		48.6		64.6
Long-term debt (including current maturities)	3,902.4		—		4,647.2		3.3		4,650.5		3,835.6		—		4,332.4		3.7		4,336.1
Cumulative preferred stock of IPL	200.0		218.3		—		—		218.3		200.0		206.6		—		—		206.6

IPL	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$28.1		$—		$1.8		$26.3		$28.1		$15.5		$—		$2.0		$13.5		$15.5
Deferred proceeds	74.4		—		—		74.4		74.4		172.0		—		—		172.0		172.0
Liabilities and equity:
Derivatives	9.8		—		1.8		8.0		9.8		23.4		—		8.0		15.4		23.4
Long-term debt (including current maturities)	1,924.8		—		2,271.3		—		2,271.3		1,856.9		—		2,092.7		—		2,092.7
Cumulative preferred stock	200.0		218.3		—		—		218.3		200.0		206.6		—		—		206.6

WPL	June 30, 2016										December 31, 2015
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$8.8		$—		$1.4		$7.4		$8.8		$2.9		$—		$0.5		$2.4		$2.9
Liabilities and equity:
Derivatives	27.3		—		2.2		25.1		27.3		41.2		—		8.0		33.2		41.2
Long-term debt (including current maturities)	1,534.6		—		1,923.5		—		1,923.5		1,533.9		—		1,793.0		—		1,793.0

Unrealized gains and losses from derivative instruments are generally recorded with offsets to regulatory assets or regulatory liabilities, based on fuel and natural gas cost recovery mechanisms, as well as other specific regulatory authorizations. 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.

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended June 30	2016			2015			2016			2015
Beginning balance, April 1		($65.9	)		($13.1	)		$154.2			$117.7
Total net gains (losses) included in changes in net assets (realized/unrealized)	44.6			(19.6		)	—			—
Transfers out of Level 3	0.4			1.0			—			—
Purchases	22.0			36.8			—			—
Sales	(0.1		)	(0.4		)	—			—
Settlements (a)	(0.4		)	(4.1		)	(79.8		)	(44.3		)
Ending balance, June 30		$0.6			$0.6			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$44.8			($17.7	)		$—			$—

Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Six Months Ended June 30	2016			2015			2016			2015
Beginning balance, January 1		($32.7	)		$17.9			$172.0			$177.2
Total net gains (losses) included in changes in net assets (realized/unrealized)	13.1			(36.8		)	—			—
Transfers into Level 3	0.9			—			—			—
Transfers out of Level 3	0.4			0.6			—			—
Purchases	22.0			36.8			—			—
Sales	(0.7		)	(1.2		)	—			—
Settlements (a)	(2.4		)	(16.7		)	(97.6		)	(103.8		)
Ending balance, June 30		$0.6			$0.6			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$14.8			($33.9	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended June 30	2016			2015			2016			2015
Beginning balance, April 1		($13.1	)		($5.0	)		$154.2			$117.7
Total net gains (losses) included in changes in net assets (realized/unrealized)	12.9			(5.0		)	—			—
Transfers out of Level 3	(0.1		)	0.2			—			—
Purchases	20.6			33.1			—			—
Sales	(0.1		)	(0.4		)	—			—
Settlements (a)	(1.9		)	(4.6		)	(79.8		)	(44.3		)
Ending balance, June 30		$18.3			$18.3			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$12.8			($4.2	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Six Months Ended June 30	2016			2015			2016			2015
Beginning balance, January 1		($1.9	)		$19.4			$172.0			$177.2
Total net gains (losses) included in changes in net assets (realized/unrealized)	5.2			(17.4		)	—			—
Transfers into Level 3	0.5			—			—			—
Transfers out of Level 3	(0.1		)	—			—			—
Purchases	20.6			33.1			—			—
Sales	(0.7		)	(1.1		)	—			—
Settlements (a)	(5.3		)	(15.7		)	(97.6		)	(103.8		)
Ending balance, June 30		$18.3			$18.3			$74.4			$73.4
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$6.2			($14.3	)		$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended June 30	2016			2015
Beginning balance, April 1		($52.8	)		($8.1	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	31.7			(14.6		)
Transfers out of Level 3	0.5			0.8
Purchases	1.4			3.7
Settlements	1.5			0.5
Ending balance, June 30		($17.7	)		($17.7	)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$32.0			($13.5	)

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Six Months Ended June 30	2016			2015
Beginning balance, January 1		($30.8	)		($1.5	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	7.9			(19.4		)
Transfers into Level 3	0.4			—
Transfers out of Level 3	0.5			0.6
Purchases	1.4			3.7
Sales	—			(0.1		)
Settlements	2.9			(1.0		)
Ending balance, June 30		($17.7	)		($17.7	)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at June 30		$8.6			($19.6	)

(a) 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.

Commodity Contracts - The fair value of electric, natural gas and coal commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):

	Alliant Energy					IPL					WPL
	Excluding FTRs			FTRs		Excluding FTRs			FTRs		Excluding FTRs			FTRs
June 30, 2016		($22.9	)		$23.5		($3.4	)		$21.7		($19.5	)		$1.8
December 31, 2015	(43.1		)	10.4		(12.3		)	10.4		(30.8		)	—