Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2012

Fair Value Disclosures [Abstract]

Fair Value Of Financial Instruments

Carrying amounts and the related estimated fair values of other financial instruments were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
September 30, 2012
Assets:
Money market fund investments		$13.6		$13.6		$1.1		$1.1		$12.5		$12.5
Derivative assets (Note 10)	46.5		46.5		28.1		28.1		18.4		18.4
Deferred proceeds (sales of receivables) (Note 3)	153.9		153.9		153.9		153.9		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 7(b))	2,829.5		3,598.7		1,359.3		1,696.1		1,082.5		1,492.4
Cumulative preferred stock of subsidiaries	205.1		215.6		145.1		154.8		60.0		60.8
Derivative liabilities (Note 10)	57.3		57.3		22.8		22.8		34.5		34.5

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
December 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

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements were as follows (Not Applicable (N/A); in millions):

Alliant Energy	September 30, 2012								December 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments		$13.6		$13.6		$—		$—		$—		$—		$—		$—
Derivatives - commodity contracts	46.5		—		11.9		34.6		15.7		—		3.4		12.3
Deferred proceeds	153.9		—		—		153.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	3,598.7		—		3,598.2		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries	215.6		165.2		50.4		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	57.3		—		40.3		17.0		78.0		—		64.8		13.2

IPL	September 30, 2012								December 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments		$1.1		$1.1		$—		$—		$—		$—		$—		$—
Derivatives - commodity contracts	28.1		—		8.1		20.0		10.6		—		1.3		9.3
Deferred proceeds	153.9		—		—		153.9		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt	1,696.1		—		1,696.1		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	154.8		154.8		—		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	22.8		—		18.3		4.5		33.6		—		28.6		5.0

WPL	September 30, 2012								December 31, 2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Money market fund investments		$12.5		$12.5		$—		$—		$—		$—		$—		$—
Derivatives - commodity contracts	18.4		—		3.8		14.6		5.1		—		2.1		3.0
Capitalization and liabilities:
Long-term debt	1,492.4		—		1,492.4		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	60.8		10.4		50.4		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	34.5		—		22.0		12.5		44.4		—		36.2		8.2

Fair Value Measurements Using Significant Unobservable Inputs

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) for the three and nine months ended September 30 was as follows (in millions):

Alliant Energy	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
Three Months Ended September 30	2012			2011			2012		2011			2012		2011
Beginning balance, July 1		$18.8			$18.1			$—		$2.1			$81.7		$66.4
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.3		)	(0.1		)	—		—			—		—
Transfers into Level 3 (b)	(0.4		)	—			—		—			—		—
Transfers out of Level 3 (c)	9.3			—			—		—			—		—
Settlements (d)	(7.8		)	(6.1		)	—		(1.7		)	72.2		21.0
Ending balance, September 30		$17.6			$11.9			$—		$0.4			$153.9		$87.4
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at September 30 (a)		($0.7	)		($0.1	)		$—		$—			$—		$—

Alliant Energy	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
Nine Months Ended September 30	2012			2011			2012		2011			2012		2011
Beginning balance, January 1		($0.9	)		$2.8			$—		$4.7			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(8.3		)	—			—		—			—		—
Transfers into Level 3 (b)	(1.7		)	0.2			—		—			—		—
Transfers out of Level 3 (c)	8.3			—			—		—			—		—
Purchases	35.8			21.8			—		—			—		—
Settlements (d)	(15.6		)	(12.9		)	—		(4.3		)	100.2		(65.5		)
Ending balance, September 30		$17.6			$11.9			$—		$0.4			$153.9		$87.4
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at September 30 (a)		($4.4	)		$—			$—		$—			$—		$—

IPL	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts				Deferred Proceeds
Three Months Ended September 30	2012			2011			2012		2011		2012		2011
Beginning balance, July 1		$14.1			$17.5			$—		$—		$81.7		$66.4
Total net losses (realized/unrealized) included in changes in net assets (a)	(0.2		)	(0.1		)	—		—		—		—
Transfers out of Level 3 (c)	7.4			—			—		—		—		—
Settlements (d)	(5.8		)	(5.0		)	—		—		72.2		21.0
Ending balance, September 30		$15.5			$12.4			$—		$—		$153.9		$87.4
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 September 30 (a)		$1.4			($0.1	)		$—		$—		$—		$—

IPL	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts					Deferred Proceeds
Nine Months Ended September 30	2012			2011			2012		2011			2012		2011
Beginning balance, January 1		$4.3			$4.3			$—		$4.8			$53.7		$152.9
Total net gains (losses) (realized/unrealized) included in changes in net assets (a)	(4.8		)	0.4			—		—			—		—
Transfers into Level 3 (b)	(1.1		)	—			—		—			—		—
Transfers out of Level 3 (c)	2.4			—			—		—			—		—
Purchases	26.8			18.1			—		—			—		—
Sales (e)	—			—			—		(2.1		)	—		—
Settlements (d)	(12.1		)	(10.4		)	—		(2.7		)	100.2		(65.5		)
Ending balance, September 30		$15.5			$12.4			$—		$—			$153.9		$87.4
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 September 30 (a)		($0.7	)		$0.4			$—		$—			$—		$—

WPL	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts
Three Months Ended September 30	2012			2011			2012		2011
Beginning balance, July 1		$4.7			$0.6			$—		$—
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.1		)	—			—		—
Transfers into Level 3 (b)	(0.4		)	—			—		—
Transfers out of Level 3 (c)	1.9			—			—		—
Settlements	(2.0		)	(1.1		)	—		—
Ending balance, September 30		$2.1			($0.5	)		$—		$—
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at September 30 (a)		($2.1	)		$—			$—		$—

WPL	Derivative Assets and (Liabilities), net
	Commodity Contracts						Foreign Contracts
Nine Months Ended September 30	2012			2011			2012		2011
Beginning balance, January 1		($5.2	)		($1.5	)		$—		($0.1	)
Total net losses (realized/unrealized) included in changes in net assets (a)	(3.5		)	(0.4		)	—		—
Transfers into Level 3 (b)	(0.6		)	0.2			—		—
Transfers out of Level 3 (c)	5.9			—			—		—
Purchases	9.0			3.7			—		—
Settlements	(3.5		)	(2.5		)	—		0.1
Ending balance, September 30		$2.1			($0.5	)		$—		$—
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at September 30 (a)		($3.7	)		($0.4	)		$—		$—

(a) Gains and 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 became inactive and observable market inputs became unavailable 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.

(e) The foreign exchange contract was transferred from IPL to Resources in connection with the sale of wind project assets in the second quarter of 2011.