Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

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 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
March 31, 2013
Assets:
Derivative assets (Note 11)		$23.6		$23.6		$12.5		$12.5		$11.1		$11.1
Deferred proceeds (sales of receivables) (Note 3(a))	122.1		122.1		122.1		122.1		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 8(b))	3,123.4		3,806.5		1,344.5		1,643.8		1,331.7		1,691.6
Cumulative preferred stock (Note 7)	200.0		201.8		200.0		201.8		—		—
Derivative liabilities (Note 11)	17.1		17.1		6.1		6.1		11.0		11.0

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
December 31, 2012
Assets:
Derivative assets (Note 11)		$26.2		$26.2		$17.5		$17.5		$8.7		$8.7
Deferred proceeds (sales of receivables) (Note 3(a))	66.8		66.8		66.8		66.8		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 8(b))	3,138.1		3,860.5		1,359.5		1,679.9		1,331.5		1,713.3
Cumulative preferred stock (Note 7)	205.1		212.6		145.1		151.8		60.0		60.8
Derivative liabilities (Note 11)	40.4		40.4		16.1		16.1		24.3		24.3

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements were as follows (in millions):

Alliant Energy	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$23.6		$—		$14.4		$9.2		$26.2		$—		$4.8		$21.4
Deferred proceeds	122.1		—		—		122.1		66.8		—		—		66.8
Capitalization and liabilities:
Long-term debt (including current maturities)	3,806.5		—		3,806.0		0.5		3,860.5		—		3,860.0		0.5
Cumulative preferred stock	201.8		201.8		—		—		212.6		162.3		50.3		—
Derivatives - commodity contracts	17.1		—		12.8		4.3		40.4		—		30.9		9.5

IPL	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$12.5		$—		$6.5		$6.0		$17.5		$—		$3.1		$14.4
Deferred proceeds	122.1		—		—		122.1		66.8		—		—		66.8
Capitalization and liabilities:
Long-term debt	1,643.8		—		1,643.8		—		1,679.9		—		1,679.9		—
Cumulative preferred stock	201.8		201.8		—		—		151.8		151.8		—		—
Derivatives - commodity contracts	6.1		—		4.4		1.7		16.1		—		14.2		1.9

WPL	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$11.1		$—		$7.9		$3.2		$8.7		$—		$1.7		$7.0
Capitalization and liabilities:
Long-term debt	1,691.6		—		1,691.6		—		1,713.3		—		1,713.3		—
Cumulative preferred stock	—		—		—		—		60.8		10.5		50.3		—
Derivatives - commodity contracts	11.0		—		8.4		2.6		24.3		—		16.7		7.6

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
Three Months Ended March 31	2013			2012			2013		2012
Beginning balance, January 1		$11.9			($0.9	)		$66.8		$53.7
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.4		)	(12.5		)	—		—
Transfers into Level 3 (b)	—			(3.8		)	—		—
Transfers out of Level 3 (c)	3.6			5.3			—		—
Settlements (d)	(8.2		)	(3.2		)	55.3		(20.8		)
Ending balance, March 31		$4.9			($15.1	)		$122.1		$32.9
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 March 31 (a)		($2.4	)		($12.5	)		$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended March 31	2013			2012			2013		2012
Beginning balance, January 1		$12.5			$4.3			$66.8		$53.7
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.9		)	(10.8		)	—		—
Transfers into Level 3 (b)	—			(2.7		)	—		—
Transfers out of Level 3 (c)	1.1			0.1			—		—
Settlements (d)	(6.4		)	(2.3		)	55.3		(20.8		)
Ending balance, March 31		$4.3			($11.4	)		$122.1		$32.9
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 March 31 (a)		($2.9	)		($10.8	)		$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended March 31	2013			2012
Beginning balance, January 1		($0.6	)		($5.2	)
Total net gains (losses) (realized/unrealized) included in changes in net assets (a)	0.5			(1.7		)
Transfers into Level 3 (b)	—			(1.1		)
Transfers out of Level 3 (c)	2.5			5.2
Settlements	(1.8		)	(0.9		)
Ending balance, March 31		$0.6			($3.7	)
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 March 31 (a)		$0.5			($1.7	)

(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.

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 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
March 31, 2013
Assets:
Derivative assets (Note 11)		$23.6		$23.6		$12.5		$12.5		$11.1		$11.1
Deferred proceeds (sales of receivables) (Note 3(a))	122.1		122.1		122.1		122.1		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 8(b))	3,123.4		3,806.5		1,344.5		1,643.8		1,331.7		1,691.6
Cumulative preferred stock (Note 7)	200.0		201.8		200.0		201.8		—		—
Derivative liabilities (Note 11)	17.1		17.1		6.1		6.1		11.0		11.0

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
December 31, 2012
Assets:
Derivative assets (Note 11)		$26.2		$26.2		$17.5		$17.5		$8.7		$8.7
Deferred proceeds (sales of receivables) (Note 3(a))	66.8		66.8		66.8		66.8		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 8(b))	3,138.1		3,860.5		1,359.5		1,679.9		1,331.5		1,713.3
Cumulative preferred stock (Note 7)	205.1		212.6		145.1		151.8		60.0		60.8
Derivative liabilities (Note 11)	40.4		40.4		16.1		16.1		24.3		24.3

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements were as follows (in millions):

Alliant Energy	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$23.6		$—		$14.4		$9.2		$26.2		$—		$4.8		$21.4
Deferred proceeds	122.1		—		—		122.1		66.8		—		—		66.8
Capitalization and liabilities:
Long-term debt (including current maturities)	3,806.5		—		3,806.0		0.5		3,860.5		—		3,860.0		0.5
Cumulative preferred stock	201.8		201.8		—		—		212.6		162.3		50.3		—
Derivatives - commodity contracts	17.1		—		12.8		4.3		40.4		—		30.9		9.5

IPL	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$12.5		$—		$6.5		$6.0		$17.5		$—		$3.1		$14.4
Deferred proceeds	122.1		—		—		122.1		66.8		—		—		66.8
Capitalization and liabilities:
Long-term debt	1,643.8		—		1,643.8		—		1,679.9		—		1,679.9		—
Cumulative preferred stock	201.8		201.8		—		—		151.8		151.8		—		—
Derivatives - commodity contracts	6.1		—		4.4		1.7		16.1		—		14.2		1.9

WPL	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$11.1		$—		$7.9		$3.2		$8.7		$—		$1.7		$7.0
Capitalization and liabilities:
Long-term debt	1,691.6		—		1,691.6		—		1,713.3		—		1,713.3		—
Cumulative preferred stock	—		—		—		—		60.8		10.5		50.3		—
Derivatives - commodity contracts	11.0		—		8.4		2.6		24.3		—		16.7		7.6

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
Three Months Ended March 31	2013			2012			2013		2012
Beginning balance, January 1		$11.9			($0.9	)		$66.8		$53.7
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.4		)	(12.5		)	—		—
Transfers into Level 3 (b)	—			(3.8		)	—		—
Transfers out of Level 3 (c)	3.6			5.3			—		—
Settlements (d)	(8.2		)	(3.2		)	55.3		(20.8		)
Ending balance, March 31		$4.9			($15.1	)		$122.1		$32.9
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 March 31 (a)		($2.4	)		($12.5	)		$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended March 31	2013			2012			2013		2012
Beginning balance, January 1		$12.5			$4.3			$66.8		$53.7
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.9		)	(10.8		)	—		—
Transfers into Level 3 (b)	—			(2.7		)	—		—
Transfers out of Level 3 (c)	1.1			0.1			—		—
Settlements (d)	(6.4		)	(2.3		)	55.3		(20.8		)
Ending balance, March 31		$4.3			($11.4	)		$122.1		$32.9
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 March 31 (a)		($2.9	)		($10.8	)		$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended March 31	2013			2012
Beginning balance, January 1		($0.6	)		($5.2	)
Total net gains (losses) (realized/unrealized) included in changes in net assets (a)	0.5			(1.7		)
Transfers into Level 3 (b)	—			(1.1		)
Transfers out of Level 3 (c)	2.5			5.2
Settlements	(1.8		)	(0.9		)
Ending balance, March 31		$0.6			($3.7	)
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 March 31 (a)		$0.5			($1.7	)

(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.

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 were as follows (in millions):

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
March 31, 2013
Assets:
Derivative assets (Note 11)		$23.6		$23.6		$12.5		$12.5		$11.1		$11.1
Deferred proceeds (sales of receivables) (Note 3(a))	122.1		122.1		122.1		122.1		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 8(b))	3,123.4		3,806.5		1,344.5		1,643.8		1,331.7		1,691.6
Cumulative preferred stock (Note 7)	200.0		201.8		200.0		201.8		—		—
Derivative liabilities (Note 11)	17.1		17.1		6.1		6.1		11.0		11.0

	Alliant Energy				IPL				WPL
	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
December 31, 2012
Assets:
Derivative assets (Note 11)		$26.2		$26.2		$17.5		$17.5		$8.7		$8.7
Deferred proceeds (sales of receivables) (Note 3(a))	66.8		66.8		66.8		66.8		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 8(b))	3,138.1		3,860.5		1,359.5		1,679.9		1,331.5		1,713.3
Cumulative preferred stock (Note 7)	205.1		212.6		145.1		151.8		60.0		60.8
Derivative liabilities (Note 11)	40.4		40.4		16.1		16.1		24.3		24.3

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements were as follows (in millions):

Alliant Energy	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$23.6		$—		$14.4		$9.2		$26.2		$—		$4.8		$21.4
Deferred proceeds	122.1		—		—		122.1		66.8		—		—		66.8
Capitalization and liabilities:
Long-term debt (including current maturities)	3,806.5		—		3,806.0		0.5		3,860.5		—		3,860.0		0.5
Cumulative preferred stock	201.8		201.8		—		—		212.6		162.3		50.3		—
Derivatives - commodity contracts	17.1		—		12.8		4.3		40.4		—		30.9		9.5

IPL	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$12.5		$—		$6.5		$6.0		$17.5		$—		$3.1		$14.4
Deferred proceeds	122.1		—		—		122.1		66.8		—		—		66.8
Capitalization and liabilities:
Long-term debt	1,643.8		—		1,643.8		—		1,679.9		—		1,679.9		—
Cumulative preferred stock	201.8		201.8		—		—		151.8		151.8		—		—
Derivatives - commodity contracts	6.1		—		4.4		1.7		16.1		—		14.2		1.9

WPL	March 31, 2013								December 31, 2012
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$11.1		$—		$7.9		$3.2		$8.7		$—		$1.7		$7.0
Capitalization and liabilities:
Long-term debt	1,691.6		—		1,691.6		—		1,713.3		—		1,713.3		—
Cumulative preferred stock	—		—		—		—		60.8		10.5		50.3		—
Derivatives - commodity contracts	11.0		—		8.4		2.6		24.3		—		16.7		7.6

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
Three Months Ended March 31	2013			2012			2013		2012
Beginning balance, January 1		$11.9			($0.9	)		$66.8		$53.7
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.4		)	(12.5		)	—		—
Transfers into Level 3 (b)	—			(3.8		)	—		—
Transfers out of Level 3 (c)	3.6			5.3			—		—
Settlements (d)	(8.2		)	(3.2		)	55.3		(20.8		)
Ending balance, March 31		$4.9			($15.1	)		$122.1		$32.9
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 March 31 (a)		($2.4	)		($12.5	)		$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended March 31	2013			2012			2013		2012
Beginning balance, January 1		$12.5			$4.3			$66.8		$53.7
Total net losses (realized/unrealized) included in changes in net assets (a)	(2.9		)	(10.8		)	—		—
Transfers into Level 3 (b)	—			(2.7		)	—		—
Transfers out of Level 3 (c)	1.1			0.1			—		—
Settlements (d)	(6.4		)	(2.3		)	55.3		(20.8		)
Ending balance, March 31		$4.3			($11.4	)		$122.1		$32.9
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 March 31 (a)		($2.9	)		($10.8	)		$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended March 31	2013			2012
Beginning balance, January 1		($0.6	)		($5.2	)
Total net gains (losses) (realized/unrealized) included in changes in net assets (a)	0.5			(1.7		)
Transfers into Level 3 (b)	—			(1.1		)
Transfers out of Level 3 (c)	2.5			5.2
Settlements	(1.8		)	(0.9		)
Ending balance, March 31		$0.6			($3.7	)
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 March 31 (a)		$0.5			($1.7	)

(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.