Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2012

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Carrying Amount and Fair Value of Financial Instruments

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
2012
Assets:
Derivative assets (Note 12)		$26.2		$26.2		$17.5		$17.5		$8.7		$8.7
Deferred proceeds (sales of receivables) (Note 4(a))	66.8		66.8		66.8		66.8		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,138.1		3,860.5		1,359.5		1,679.9		1,331.5		1,713.3
Cumulative preferred stock of subsidiaries (Note 8)	205.1		212.6		145.1		151.8		60.0		60.8
Derivative liabilities (Note 12)	40.4		40.4		16.1		16.1		24.3		24.3
2011
Assets:
Derivative assets (Note 12)	15.7		15.7		10.6		10.6		5.1		5.1
Deferred proceeds (sales of receivables) (Note 4(a))	53.7		53.7		53.7		53.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	2,704.5		3,325.3		1,309.0		1,560.4		1,082.2		1,439.0
Cumulative preferred stock of subsidiaries (Note 8)	205.1		222.5		145.1		164.3		60.0		58.2
Derivative liabilities (Note 12)	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	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$26.2		$—		$4.8		$21.4		$15.7		$—		$3.4		$12.3
Deferred proceeds	66.8		—		—		66.8		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	3,860.5		—		3,860.0		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries	212.6		162.3		50.3		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	40.4		—		30.9		9.5		78.0		—		64.8		13.2

IPL	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$17.5		$—		$3.1		$14.4		$10.6		$—		$1.3		$9.3
Deferred proceeds	66.8		—		—		66.8		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	1,679.9		—		1,679.9		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	151.8		151.8		—		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	16.1		—		14.2		1.9		33.6		—		28.6		5.0

WPL	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$8.7		$—		$1.7		$7.0		$5.1		$—		$2.1		$3.0
Capitalization and liabilities:
Long-term debt (including current maturities)	1,713.3		—		1,713.3		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	60.8		10.5		50.3		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	24.3		—		16.7		7.6		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) was as follows (in millions):

Alliant Energy	Commodity Contract
	Derivative Assets and
	(Liabilities), net						Deferred Proceeds
	2012			2011			2012		2011
Beginning balance, January 1		($0.9	)		$2.8			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(7.6		)	(7.3		)	—		—
Transfers into Level 3 (b)	(1.1		)	0.2			—		—
Transfers out of Level 3 (c)	8.3			—			—		—
Purchases	35.8			21.8			—		—
Settlements (d)	(22.6		)	(18.4		)	13.1		(99.2		)
Ending balance, December 31		$11.9			($0.9	)		$66.8		$53.7
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 December 31 (a)		($2.6	)		($7.3	)		$—		$—

IPL	Commodity Contract
	Derivative Assets and
	(Liabilities), net						Deferred Proceeds
	2012			2011			2012		2011
Beginning balance, January 1		$4.3			$4.3			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(3.5		)	(3.1		)	—		—
Transfers into Level 3 (b)	(1.1		)	—			—		—
Transfers out of Level 3 (c)	2.4			—			—		—
Purchases	26.8			18.1			—		—
Settlements (d)	(16.4		)	(15.0		)	13.1		(99.2		)
Ending balance, December 31		$12.5			$4.3			$66.8		$53.7
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 December 31 (a)		$1.5			($3.1	)		$—		$—

WPL	Commodity Contract
	Derivative Assets and
	(Liabilities), net
	2012			2011
Beginning balance, January 1		($5.2	)		($1.5	)
Total net losses (realized/unrealized) included in changes in net assets (a)	(4.1		)	(4.2		)
Transfers into Level 3 (b)	—			0.2
Transfers out of Level 3 (c)	5.9			—
Purchases	9.0			3.7
Settlements	(6.2		)	(3.4		)
Ending balance, December 31		($0.6	)		($5.2	)
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 December 31 (a)		($4.1	)		($4.2	)

(a) Gains and losses related to derivative assets and derivative liabilities are generally recorded in “Regulatory assets” and “Regulatory liabilities” on the 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.

IPL [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Carrying Amount and Fair Value of Financial Instruments

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
2012
Assets:
Derivative assets (Note 12)		$26.2		$26.2		$17.5		$17.5		$8.7		$8.7
Deferred proceeds (sales of receivables) (Note 4(a))	66.8		66.8		66.8		66.8		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,138.1		3,860.5		1,359.5		1,679.9		1,331.5		1,713.3
Cumulative preferred stock of subsidiaries (Note 8)	205.1		212.6		145.1		151.8		60.0		60.8
Derivative liabilities (Note 12)	40.4		40.4		16.1		16.1		24.3		24.3
2011
Assets:
Derivative assets (Note 12)	15.7		15.7		10.6		10.6		5.1		5.1
Deferred proceeds (sales of receivables) (Note 4(a))	53.7		53.7		53.7		53.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	2,704.5		3,325.3		1,309.0		1,560.4		1,082.2		1,439.0
Cumulative preferred stock of subsidiaries (Note 8)	205.1		222.5		145.1		164.3		60.0		58.2
Derivative liabilities (Note 12)	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	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$26.2		$—		$4.8		$21.4		$15.7		$—		$3.4		$12.3
Deferred proceeds	66.8		—		—		66.8		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	3,860.5		—		3,860.0		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries	212.6		162.3		50.3		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	40.4		—		30.9		9.5		78.0		—		64.8		13.2

IPL	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$17.5		$—		$3.1		$14.4		$10.6		$—		$1.3		$9.3
Deferred proceeds	66.8		—		—		66.8		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	1,679.9		—		1,679.9		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	151.8		151.8		—		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	16.1		—		14.2		1.9		33.6		—		28.6		5.0

WPL	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$8.7		$—		$1.7		$7.0		$5.1		$—		$2.1		$3.0
Capitalization and liabilities:
Long-term debt (including current maturities)	1,713.3		—		1,713.3		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	60.8		10.5		50.3		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	24.3		—		16.7		7.6		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) was as follows (in millions):

Alliant Energy	Commodity Contract
	Derivative Assets and
	(Liabilities), net						Deferred Proceeds
	2012			2011			2012		2011
Beginning balance, January 1		($0.9	)		$2.8			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(7.6		)	(7.3		)	—		—
Transfers into Level 3 (b)	(1.1		)	0.2			—		—
Transfers out of Level 3 (c)	8.3			—			—		—
Purchases	35.8			21.8			—		—
Settlements (d)	(22.6		)	(18.4		)	13.1		(99.2		)
Ending balance, December 31		$11.9			($0.9	)		$66.8		$53.7
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 December 31 (a)		($2.6	)		($7.3	)		$—		$—

IPL	Commodity Contract
	Derivative Assets and
	(Liabilities), net						Deferred Proceeds
	2012			2011			2012		2011
Beginning balance, January 1		$4.3			$4.3			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(3.5		)	(3.1		)	—		—
Transfers into Level 3 (b)	(1.1		)	—			—		—
Transfers out of Level 3 (c)	2.4			—			—		—
Purchases	26.8			18.1			—		—
Settlements (d)	(16.4		)	(15.0		)	13.1		(99.2		)
Ending balance, December 31		$12.5			$4.3			$66.8		$53.7
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 December 31 (a)		$1.5			($3.1	)		$—		$—

WPL	Commodity Contract
	Derivative Assets and
	(Liabilities), net
	2012			2011
Beginning balance, January 1		($5.2	)		($1.5	)
Total net losses (realized/unrealized) included in changes in net assets (a)	(4.1		)	(4.2		)
Transfers into Level 3 (b)	—			0.2
Transfers out of Level 3 (c)	5.9			—
Purchases	9.0			3.7
Settlements	(6.2		)	(3.4		)
Ending balance, December 31		($0.6	)		($5.2	)
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 December 31 (a)		($4.1	)		($4.2	)

(a) Gains and losses related to derivative assets and derivative liabilities are generally recorded in “Regulatory assets” and “Regulatory liabilities” on the 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.

WPL [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Carrying Amount and Fair Value of Financial Instruments

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
2012
Assets:
Derivative assets (Note 12)		$26.2		$26.2		$17.5		$17.5		$8.7		$8.7
Deferred proceeds (sales of receivables) (Note 4(a))	66.8		66.8		66.8		66.8		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,138.1		3,860.5		1,359.5		1,679.9		1,331.5		1,713.3
Cumulative preferred stock of subsidiaries (Note 8)	205.1		212.6		145.1		151.8		60.0		60.8
Derivative liabilities (Note 12)	40.4		40.4		16.1		16.1		24.3		24.3
2011
Assets:
Derivative assets (Note 12)	15.7		15.7		10.6		10.6		5.1		5.1
Deferred proceeds (sales of receivables) (Note 4(a))	53.7		53.7		53.7		53.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	2,704.5		3,325.3		1,309.0		1,560.4		1,082.2		1,439.0
Cumulative preferred stock of subsidiaries (Note 8)	205.1		222.5		145.1		164.3		60.0		58.2
Derivative liabilities (Note 12)	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	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$26.2		$—		$4.8		$21.4		$15.7		$—		$3.4		$12.3
Deferred proceeds	66.8		—		—		66.8		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	3,860.5		—		3,860.0		0.5		N/A		N/A		N/A		N/A
Cumulative preferred stock of subsidiaries	212.6		162.3		50.3		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	40.4		—		30.9		9.5		78.0		—		64.8		13.2

IPL	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$17.5		$—		$3.1		$14.4		$10.6		$—		$1.3		$9.3
Deferred proceeds	66.8		—		—		66.8		53.7		—		—		53.7
Capitalization and liabilities:
Long-term debt (including current maturities)	1,679.9		—		1,679.9		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	151.8		151.8		—		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	16.1		—		14.2		1.9		33.6		—		28.6		5.0

WPL	2012								2011
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$8.7		$—		$1.7		$7.0		$5.1		$—		$2.1		$3.0
Capitalization and liabilities:
Long-term debt (including current maturities)	1,713.3		—		1,713.3		—		N/A		N/A		N/A		N/A
Cumulative preferred stock	60.8		10.5		50.3		—		N/A		N/A		N/A		N/A
Derivatives - commodity contracts	24.3		—		16.7		7.6		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) was as follows (in millions):

Alliant Energy	Commodity Contract
	Derivative Assets and
	(Liabilities), net						Deferred Proceeds
	2012			2011			2012		2011
Beginning balance, January 1		($0.9	)		$2.8			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(7.6		)	(7.3		)	—		—
Transfers into Level 3 (b)	(1.1		)	0.2			—		—
Transfers out of Level 3 (c)	8.3			—			—		—
Purchases	35.8			21.8			—		—
Settlements (d)	(22.6		)	(18.4		)	13.1		(99.2		)
Ending balance, December 31		$11.9			($0.9	)		$66.8		$53.7
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 December 31 (a)		($2.6	)		($7.3	)		$—		$—

IPL	Commodity Contract
	Derivative Assets and
	(Liabilities), net						Deferred Proceeds
	2012			2011			2012		2011
Beginning balance, January 1		$4.3			$4.3			$53.7		$152.9
Total net losses (realized/unrealized) included in changes in net assets (a)	(3.5		)	(3.1		)	—		—
Transfers into Level 3 (b)	(1.1		)	—			—		—
Transfers out of Level 3 (c)	2.4			—			—		—
Purchases	26.8			18.1			—		—
Settlements (d)	(16.4		)	(15.0		)	13.1		(99.2		)
Ending balance, December 31		$12.5			$4.3			$66.8		$53.7
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 December 31 (a)		$1.5			($3.1	)		$—		$—

WPL	Commodity Contract
	Derivative Assets and
	(Liabilities), net
	2012			2011
Beginning balance, January 1		($5.2	)		($1.5	)
Total net losses (realized/unrealized) included in changes in net assets (a)	(4.1		)	(4.2		)
Transfers into Level 3 (b)	—			0.2
Transfers out of Level 3 (c)	5.9			—
Purchases	9.0			3.7
Settlements	(6.2		)	(3.4		)
Ending balance, December 31		($0.6	)		($5.2	)
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 December 31 (a)		($4.1	)		($4.2	)

(a) Gains and losses related to derivative assets and derivative liabilities are generally recorded in “Regulatory assets” and “Regulatory liabilities” on the 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.