Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

Statement [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
March 31, 2015	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Assets:
Derivative assets (Note 12)		$16.9		$16.9		$6.5		$6.5		$10.4		$10.4
Deferred proceeds (sales of receivables) (Note 4(a))	117.7		117.7		117.7		117.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities)	3,789.7		4,490.4		1,768.8		2,092.9		1,574.0		1,938.9
Cumulative preferred stock	200.0		203.7		200.0		203.7		—		—
Derivative liabilities (Note 12)	42.7		42.7		20.0		20.0		22.7		22.7

	Alliant Energy				IPL				WPL
December 31, 2014	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Assets:
Derivative assets (Note 12)		$38.6		$38.6		$28.0		$28.0		$10.6		$10.6
Deferred proceeds (sales of receivables) (Note 4(a))	177.2		177.2		177.2		177.2		—		—
Capitalization and liabilities:
Long-term debt (including current maturities)	3,789.7		4,418.2		1,768.7		2,053.0		1,573.9		1,908.9
Cumulative preferred stock	200.0		200.2		200.0		200.2		—		—
Derivative liabilities (Note 12)	37.6		37.6		19.5		19.5		18.1		18.1

Fair Value Measurements

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

Alliant Energy	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$16.9		$—		$2.2		$14.7		$38.6		$—		$2.6		$36.0
Deferred proceeds	117.7		—		—		117.7		177.2		—		—		177.2
Capitalization and liabilities:
Long-term debt (including current maturities)	4,490.4		—		4,487.4		3.0		4,418.2		—		4,414.9		3.3
Cumulative preferred stock	203.7		203.7		—		—		200.2		200.2		—		—
Derivatives - commodity contracts	42.7		—		14.9		27.8		37.6		—		19.5		18.1

IPL	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$6.5		$—		$1.7		$4.8		$28.0		$—		$2.4		$25.6
Deferred proceeds	117.7		—		—		117.7		177.2		—		—		177.2
Capitalization and liabilities:
Long-term debt (including current maturities)	2,092.9		—		2,092.9		—		2,053.0		—		2,053.0		—
Cumulative preferred stock	203.7		203.7		—		—		200.2		200.2		—		—
Derivatives - commodity contracts	20.0		—		10.2		9.8		19.5		—		13.3		6.2

WPL	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$10.4		$—		$0.5		$9.9		$10.6		$—		$0.2		$10.4
Capitalization and liabilities:
Long-term debt (including current maturities)	1,938.9		—		1,938.9		—		1,908.9		—		1,908.9		—
Derivatives - commodity contracts	22.7		—		4.7		18.0		18.1		—		6.2		11.9

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	2015			2014			2015			2014
Beginning balance, January 1		$17.9			$4.4			$177.2			$203.5
Total net gains (losses) (realized/unrealized) included in changes in net assets	(18.1		)	38.4			—			—
Sales	(0.9		)	—			—			—
Settlements (a)	(12.0		)	(18.9		)	(59.5		)	(32.7		)
Ending balance, March 31		($13.1	)		$23.9			$117.7			$170.8
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		($16.5	)		$31.0			$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended March 31	2015			2014			2015			2014
Beginning balance, January 1		$19.4			$14.6			$177.2			$203.5
Total net gains (losses) (realized/unrealized) included in changes in net assets	(12.5		)	4.2			—			—
Sales	(0.9		)	—			—			—
Settlements (a)	(11.0		)	(11.0		)	(59.5		)	(32.7		)
Ending balance, March 31		($5.0	)		$7.8			$117.7			$170.8
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		($10.7	)		$3.1			$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended March 31	2015			2014
Beginning balance, January 1		($1.5	)		($10.2	)
Total net gains (losses) (realized/unrealized) included in changes in net assets	(5.6		)	34.2
Settlements	(1.0		)	(7.9		)
Ending balance, March 31		($8.1	)		$16.1
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		($5.8	)		$27.9

(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.

Fair Value Of Net Derivative Assets (Liabilities)

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
March 31, 2015		($17.2	)		$4.1		($8.5	)		$3.5		($8.7	)		$0.6
December 31, 2014	(7.0		)	24.9		(3.2		)	22.6		(3.8		)	2.3

IPL [Member]

Statement [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
March 31, 2015	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Assets:
Derivative assets (Note 12)		$16.9		$16.9		$6.5		$6.5		$10.4		$10.4
Deferred proceeds (sales of receivables) (Note 4(a))	117.7		117.7		117.7		117.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities)	3,789.7		4,490.4		1,768.8		2,092.9		1,574.0		1,938.9
Cumulative preferred stock	200.0		203.7		200.0		203.7		—		—
Derivative liabilities (Note 12)	42.7		42.7		20.0		20.0		22.7		22.7

	Alliant Energy				IPL				WPL
December 31, 2014	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Assets:
Derivative assets (Note 12)		$38.6		$38.6		$28.0		$28.0		$10.6		$10.6
Deferred proceeds (sales of receivables) (Note 4(a))	177.2		177.2		177.2		177.2		—		—
Capitalization and liabilities:
Long-term debt (including current maturities)	3,789.7		4,418.2		1,768.7		2,053.0		1,573.9		1,908.9
Cumulative preferred stock	200.0		200.2		200.0		200.2		—		—
Derivative liabilities (Note 12)	37.6		37.6		19.5		19.5		18.1		18.1

Fair Value Measurements

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

Alliant Energy	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$16.9		$—		$2.2		$14.7		$38.6		$—		$2.6		$36.0
Deferred proceeds	117.7		—		—		117.7		177.2		—		—		177.2
Capitalization and liabilities:
Long-term debt (including current maturities)	4,490.4		—		4,487.4		3.0		4,418.2		—		4,414.9		3.3
Cumulative preferred stock	203.7		203.7		—		—		200.2		200.2		—		—
Derivatives - commodity contracts	42.7		—		14.9		27.8		37.6		—		19.5		18.1

IPL	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$6.5		$—		$1.7		$4.8		$28.0		$—		$2.4		$25.6
Deferred proceeds	117.7		—		—		117.7		177.2		—		—		177.2
Capitalization and liabilities:
Long-term debt (including current maturities)	2,092.9		—		2,092.9		—		2,053.0		—		2,053.0		—
Cumulative preferred stock	203.7		203.7		—		—		200.2		200.2		—		—
Derivatives - commodity contracts	20.0		—		10.2		9.8		19.5		—		13.3		6.2

WPL	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$10.4		$—		$0.5		$9.9		$10.6		$—		$0.2		$10.4
Capitalization and liabilities:
Long-term debt (including current maturities)	1,938.9		—		1,938.9		—		1,908.9		—		1,908.9		—
Derivatives - commodity contracts	22.7		—		4.7		18.0		18.1		—		6.2		11.9

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	2015			2014			2015			2014
Beginning balance, January 1		$17.9			$4.4			$177.2			$203.5
Total net gains (losses) (realized/unrealized) included in changes in net assets	(18.1		)	38.4			—			—
Sales	(0.9		)	—			—			—
Settlements (a)	(12.0		)	(18.9		)	(59.5		)	(32.7		)
Ending balance, March 31		($13.1	)		$23.9			$117.7			$170.8
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		($16.5	)		$31.0			$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended March 31	2015			2014			2015			2014
Beginning balance, January 1		$19.4			$14.6			$177.2			$203.5
Total net gains (losses) (realized/unrealized) included in changes in net assets	(12.5		)	4.2			—			—
Sales	(0.9		)	—			—			—
Settlements (a)	(11.0		)	(11.0		)	(59.5		)	(32.7		)
Ending balance, March 31		($5.0	)		$7.8			$117.7			$170.8
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		($10.7	)		$3.1			$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended March 31	2015			2014
Beginning balance, January 1		($1.5	)		($10.2	)
Total net gains (losses) (realized/unrealized) included in changes in net assets	(5.6		)	34.2
Settlements	(1.0		)	(7.9		)
Ending balance, March 31		($8.1	)		$16.1
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		($5.8	)		$27.9

(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.

Fair Value Of Net Derivative Assets (Liabilities)

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
March 31, 2015		($17.2	)		$4.1		($8.5	)		$3.5		($8.7	)		$0.6
December 31, 2014	(7.0		)	24.9		(3.2		)	22.6		(3.8		)	2.3

WPL [Member]

Statement [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
March 31, 2015	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Assets:
Derivative assets (Note 12)		$16.9		$16.9		$6.5		$6.5		$10.4		$10.4
Deferred proceeds (sales of receivables) (Note 4(a))	117.7		117.7		117.7		117.7		—		—
Capitalization and liabilities:
Long-term debt (including current maturities)	3,789.7		4,490.4		1,768.8		2,092.9		1,574.0		1,938.9
Cumulative preferred stock	200.0		203.7		200.0		203.7		—		—
Derivative liabilities (Note 12)	42.7		42.7		20.0		20.0		22.7		22.7

	Alliant Energy				IPL				WPL
December 31, 2014	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Assets:
Derivative assets (Note 12)		$38.6		$38.6		$28.0		$28.0		$10.6		$10.6
Deferred proceeds (sales of receivables) (Note 4(a))	177.2		177.2		177.2		177.2		—		—
Capitalization and liabilities:
Long-term debt (including current maturities)	3,789.7		4,418.2		1,768.7		2,053.0		1,573.9		1,908.9
Cumulative preferred stock	200.0		200.2		200.0		200.2		—		—
Derivative liabilities (Note 12)	37.6		37.6		19.5		19.5		18.1		18.1

Fair Value Measurements

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

Alliant Energy	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$16.9		$—		$2.2		$14.7		$38.6		$—		$2.6		$36.0
Deferred proceeds	117.7		—		—		117.7		177.2		—		—		177.2
Capitalization and liabilities:
Long-term debt (including current maturities)	4,490.4		—		4,487.4		3.0		4,418.2		—		4,414.9		3.3
Cumulative preferred stock	203.7		203.7		—		—		200.2		200.2		—		—
Derivatives - commodity contracts	42.7		—		14.9		27.8		37.6		—		19.5		18.1

IPL	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$6.5		$—		$1.7		$4.8		$28.0		$—		$2.4		$25.6
Deferred proceeds	117.7		—		—		117.7		177.2		—		—		177.2
Capitalization and liabilities:
Long-term debt (including current maturities)	2,092.9		—		2,092.9		—		2,053.0		—		2,053.0		—
Cumulative preferred stock	203.7		203.7		—		—		200.2		200.2		—		—
Derivatives - commodity contracts	20.0		—		10.2		9.8		19.5		—		13.3		6.2

WPL	March 31, 2015								December 31, 2014
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$10.4		$—		$0.5		$9.9		$10.6		$—		$0.2		$10.4
Capitalization and liabilities:
Long-term debt (including current maturities)	1,938.9		—		1,938.9		—		1,908.9		—		1,908.9		—
Derivatives - commodity contracts	22.7		—		4.7		18.0		18.1		—		6.2		11.9

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	2015			2014			2015			2014
Beginning balance, January 1		$17.9			$4.4			$177.2			$203.5
Total net gains (losses) (realized/unrealized) included in changes in net assets	(18.1		)	38.4			—			—
Sales	(0.9		)	—			—			—
Settlements (a)	(12.0		)	(18.9		)	(59.5		)	(32.7		)
Ending balance, March 31		($13.1	)		$23.9			$117.7			$170.8
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		($16.5	)		$31.0			$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
Three Months Ended March 31	2015			2014			2015			2014
Beginning balance, January 1		$19.4			$14.6			$177.2			$203.5
Total net gains (losses) (realized/unrealized) included in changes in net assets	(12.5		)	4.2			—			—
Sales	(0.9		)	—			—			—
Settlements (a)	(11.0		)	(11.0		)	(59.5		)	(32.7		)
Ending balance, March 31		($5.0	)		$7.8			$117.7			$170.8
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		($10.7	)		$3.1			$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended March 31	2015			2014
Beginning balance, January 1		($1.5	)		($10.2	)
Total net gains (losses) (realized/unrealized) included in changes in net assets	(5.6		)	34.2
Settlements	(1.0		)	(7.9		)
Ending balance, March 31		($8.1	)		$16.1
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		($5.8	)		$27.9

(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.

Fair Value Of Net Derivative Assets (Liabilities)

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
March 31, 2015		($17.2	)		$4.1		($8.5	)		$3.5		($8.7	)		$0.6
December 31, 2014	(7.0		)	24.9		(3.2		)	22.6		(3.8		)	2.3