Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

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
2014
Assets:
Derivative assets (Note 15)		$38.6		$38.6		$28.0		$28.0		$10.6		$10.6
Deferred proceeds (sales of receivables) (Note 5(b))	177.2		177.2		177.2		177.2		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,789.7		4,418.2		1,768.7		2,053.0		1,573.9		1,908.9
Cumulative preferred stock (Note 8)	200.0		200.2		200.0		200.2		—		—
Derivative liabilities (Note 15)	37.6		37.6		19.5		19.5		18.1		18.1
2013
Assets:
Derivative assets (Note 15)	26.7		26.7		21.1		21.1		5.6		5.6
Deferred proceeds (sales of receivables) (Note 5(b))	203.5		203.5		203.5		203.5		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,336.3		3,712.3		1,558.4		1,726.4		1,332.1		1,532.9
Cumulative preferred stock (Note 8)	200.0		167.0		200.0		167.0		—		—
Derivative liabilities (Note 15)	20.8		20.8		5.2		5.2		15.6		15.6

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements at December 31 were as follows (in millions):

Alliant Energy	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$38.6		$—		$2.6		$36.0		$26.7		$—		$4.7		$22.0
Deferred proceeds	177.2		—		—		177.2		203.5		—		—		203.5
Capitalization and liabilities:
Long-term debt (including current maturities)	4,418.2		—		4,414.9		3.3		3,712.3		—		3,711.8		0.5
Cumulative preferred stock	200.2		200.2		—		—		167.0		167.0		—		—
Derivatives - commodity contracts	37.6		—		19.5		18.1		20.8		—		3.2		17.6

IPL	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$28.0		$—		$2.4		$25.6		$21.1		$—		$3.0		$18.1
Deferred proceeds	177.2		—		—		177.2		203.5		—		—		203.5
Capitalization and liabilities:
Long-term debt (including current maturities)	2,053.0		—		2,053.0		—		1,726.4		—		1,726.4		—
Cumulative preferred stock	200.2		200.2		—		—		167.0		167.0		—		—
Derivatives - commodity contracts	19.5		—		13.3		6.2		5.2		—		1.7		3.5

WPL	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$10.6		$—		$0.2		$10.4		$5.6		$—		$1.7		$3.9
Capitalization and liabilities:
Long-term debt (including current maturities)	1,908.9		—		1,908.9		—		1,532.9		—		1,532.9		—
Derivatives - commodity contracts	18.1		—		6.2		11.9		15.6		—		1.5		14.1

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
	2014			2013			2014			2013
Beginning balance, January 1		$4.4			$11.9			$203.5			$66.8
Total net gains (losses) (realized/unrealized) included in changes in net assets	11.1			(12.7		)	—			—
Transfers into Level 3 (a)	—			0.1			—			—
Transfers out of Level 3 (b)	—			2.0			—			—
Purchases	76.7			50.9			—			—
Sales	(2.2		)	—			—			—
Settlements (c)	(72.1		)	(47.8		)	(26.3		)	136.7
Ending balance, December 31		$17.9			$4.4			$177.2			$203.5
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 December 31		($0.4	)		($12.7	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
	2014			2013			2014			2013
Beginning balance, January 1		$14.6			$12.5			$203.5			$66.8
Total net losses (realized/unrealized) included in changes in net assets	(5.9		)	(4.6		)	—			—
Transfers out of Level 3 (b)	—			1.0			—			—
Purchases	68.8			46.1			—			—
Sales	(2.0		)	—			—			—
Settlements (c)	(56.1		)	(40.4		)	(26.3		)	136.7
Ending balance, December 31		$19.4			$14.6			$177.2			$203.5
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 December 31		($9.3	)		($4.6	)		$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2014			2013
Beginning balance, January 1		($10.2	)		($0.6	)
Total net gains (losses) (realized/unrealized) included in changes in net assets	17.0			(8.1		)
Transfers into Level 3 (a)	—			0.1
Transfers out of Level 3 (b)	—			1.0
Purchases	7.9			4.8
Sales	(0.2		)	—
Settlements	(16.0		)	(7.4		)
Ending balance, December 31		($1.5	)		($10.2	)
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		$8.9			($8.1	)

(a) 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.

(b) 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.

(c) 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) at December 31 as follows (in millions):

	Alliant Energy					IPL					WPL
	Excluding FTRs			FTRs		Excluding FTRs			FTRs		Excluding FTRs			FTRs
2014		($7.0	)		$24.9		($3.2	)		$22.6		($3.8	)		$2.3
2013	(13.9		)	18.3		(2.1		)	16.7		(11.8		)	1.6

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
2014
Assets:
Derivative assets (Note 15)		$38.6		$38.6		$28.0		$28.0		$10.6		$10.6
Deferred proceeds (sales of receivables) (Note 5(b))	177.2		177.2		177.2		177.2		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,789.7		4,418.2		1,768.7		2,053.0		1,573.9		1,908.9
Cumulative preferred stock (Note 8)	200.0		200.2		200.0		200.2		—		—
Derivative liabilities (Note 15)	37.6		37.6		19.5		19.5		18.1		18.1
2013
Assets:
Derivative assets (Note 15)	26.7		26.7		21.1		21.1		5.6		5.6
Deferred proceeds (sales of receivables) (Note 5(b))	203.5		203.5		203.5		203.5		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,336.3		3,712.3		1,558.4		1,726.4		1,332.1		1,532.9
Cumulative preferred stock (Note 8)	200.0		167.0		200.0		167.0		—		—
Derivative liabilities (Note 15)	20.8		20.8		5.2		5.2		15.6		15.6

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements at December 31 were as follows (in millions):

Alliant Energy	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$38.6		$—		$2.6		$36.0		$26.7		$—		$4.7		$22.0
Deferred proceeds	177.2		—		—		177.2		203.5		—		—		203.5
Capitalization and liabilities:
Long-term debt (including current maturities)	4,418.2		—		4,414.9		3.3		3,712.3		—		3,711.8		0.5
Cumulative preferred stock	200.2		200.2		—		—		167.0		167.0		—		—
Derivatives - commodity contracts	37.6		—		19.5		18.1		20.8		—		3.2		17.6

IPL	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$28.0		$—		$2.4		$25.6		$21.1		$—		$3.0		$18.1
Deferred proceeds	177.2		—		—		177.2		203.5		—		—		203.5
Capitalization and liabilities:
Long-term debt (including current maturities)	2,053.0		—		2,053.0		—		1,726.4		—		1,726.4		—
Cumulative preferred stock	200.2		200.2		—		—		167.0		167.0		—		—
Derivatives - commodity contracts	19.5		—		13.3		6.2		5.2		—		1.7		3.5

WPL	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$10.6		$—		$0.2		$10.4		$5.6		$—		$1.7		$3.9
Capitalization and liabilities:
Long-term debt (including current maturities)	1,908.9		—		1,908.9		—		1,532.9		—		1,532.9		—
Derivatives - commodity contracts	18.1		—		6.2		11.9		15.6		—		1.5		14.1

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
	2014			2013			2014			2013
Beginning balance, January 1		$4.4			$11.9			$203.5			$66.8
Total net gains (losses) (realized/unrealized) included in changes in net assets	11.1			(12.7		)	—			—
Transfers into Level 3 (a)	—			0.1			—			—
Transfers out of Level 3 (b)	—			2.0			—			—
Purchases	76.7			50.9			—			—
Sales	(2.2		)	—			—			—
Settlements (c)	(72.1		)	(47.8		)	(26.3		)	136.7
Ending balance, December 31		$17.9			$4.4			$177.2			$203.5
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 December 31		($0.4	)		($12.7	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
	2014			2013			2014			2013
Beginning balance, January 1		$14.6			$12.5			$203.5			$66.8
Total net losses (realized/unrealized) included in changes in net assets	(5.9		)	(4.6		)	—			—
Transfers out of Level 3 (b)	—			1.0			—			—
Purchases	68.8			46.1			—			—
Sales	(2.0		)	—			—			—
Settlements (c)	(56.1		)	(40.4		)	(26.3		)	136.7
Ending balance, December 31		$19.4			$14.6			$177.2			$203.5
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 December 31		($9.3	)		($4.6	)		$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2014			2013
Beginning balance, January 1		($10.2	)		($0.6	)
Total net gains (losses) (realized/unrealized) included in changes in net assets	17.0			(8.1		)
Transfers into Level 3 (a)	—			0.1
Transfers out of Level 3 (b)	—			1.0
Purchases	7.9			4.8
Sales	(0.2		)	—
Settlements	(16.0		)	(7.4		)
Ending balance, December 31		($1.5	)		($10.2	)
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		$8.9			($8.1	)

(a) 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.

(b) 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.

(c) 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) at December 31 as follows (in millions):

	Alliant Energy					IPL					WPL
	Excluding FTRs			FTRs		Excluding FTRs			FTRs		Excluding FTRs			FTRs
2014		($7.0	)		$24.9		($3.2	)		$22.6		($3.8	)		$2.3
2013	(13.9		)	18.3		(2.1		)	16.7		(11.8		)	1.6

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
2014
Assets:
Derivative assets (Note 15)		$38.6		$38.6		$28.0		$28.0		$10.6		$10.6
Deferred proceeds (sales of receivables) (Note 5(b))	177.2		177.2		177.2		177.2		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,789.7		4,418.2		1,768.7		2,053.0		1,573.9		1,908.9
Cumulative preferred stock (Note 8)	200.0		200.2		200.0		200.2		—		—
Derivative liabilities (Note 15)	37.6		37.6		19.5		19.5		18.1		18.1
2013
Assets:
Derivative assets (Note 15)	26.7		26.7		21.1		21.1		5.6		5.6
Deferred proceeds (sales of receivables) (Note 5(b))	203.5		203.5		203.5		203.5		—		—
Capitalization and liabilities:
Long-term debt (including current maturities) (Note 9(b))	3,336.3		3,712.3		1,558.4		1,726.4		1,332.1		1,532.9
Cumulative preferred stock (Note 8)	200.0		167.0		200.0		167.0		—		—
Derivative liabilities (Note 15)	20.8		20.8		5.2		5.2		15.6		15.6

Recurring Fair Value Measurements

Items subject to fair value measurement disclosure requirements at December 31 were as follows (in millions):

Alliant Energy	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$38.6		$—		$2.6		$36.0		$26.7		$—		$4.7		$22.0
Deferred proceeds	177.2		—		—		177.2		203.5		—		—		203.5
Capitalization and liabilities:
Long-term debt (including current maturities)	4,418.2		—		4,414.9		3.3		3,712.3		—		3,711.8		0.5
Cumulative preferred stock	200.2		200.2		—		—		167.0		167.0		—		—
Derivatives - commodity contracts	37.6		—		19.5		18.1		20.8		—		3.2		17.6

IPL	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$28.0		$—		$2.4		$25.6		$21.1		$—		$3.0		$18.1
Deferred proceeds	177.2		—		—		177.2		203.5		—		—		203.5
Capitalization and liabilities:
Long-term debt (including current maturities)	2,053.0		—		2,053.0		—		1,726.4		—		1,726.4		—
Cumulative preferred stock	200.2		200.2		—		—		167.0		167.0		—		—
Derivatives - commodity contracts	19.5		—		13.3		6.2		5.2		—		1.7		3.5

WPL	2014								2013
	Fair		Level		Level		Level		Fair		Level		Level		Level
	Value		1		2		3		Value		1		2		3
Assets:
Derivatives - commodity contracts		$10.6		$—		$0.2		$10.4		$5.6		$—		$1.7		$3.9
Capitalization and liabilities:
Long-term debt (including current maturities)	1,908.9		—		1,908.9		—		1,532.9		—		1,532.9		—
Derivatives - commodity contracts	18.1		—		6.2		11.9		15.6		—		1.5		14.1

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
	2014			2013			2014			2013
Beginning balance, January 1		$4.4			$11.9			$203.5			$66.8
Total net gains (losses) (realized/unrealized) included in changes in net assets	11.1			(12.7		)	—			—
Transfers into Level 3 (a)	—			0.1			—			—
Transfers out of Level 3 (b)	—			2.0			—			—
Purchases	76.7			50.9			—			—
Sales	(2.2		)	—			—			—
Settlements (c)	(72.1		)	(47.8		)	(26.3		)	136.7
Ending balance, December 31		$17.9			$4.4			$177.2			$203.5
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 December 31		($0.4	)		($12.7	)		$—			$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
	2014			2013			2014			2013
Beginning balance, January 1		$14.6			$12.5			$203.5			$66.8
Total net losses (realized/unrealized) included in changes in net assets	(5.9		)	(4.6		)	—			—
Transfers out of Level 3 (b)	—			1.0			—			—
Purchases	68.8			46.1			—			—
Sales	(2.0		)	—			—			—
Settlements (c)	(56.1		)	(40.4		)	(26.3		)	136.7
Ending balance, December 31		$19.4			$14.6			$177.2			$203.5
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 December 31		($9.3	)		($4.6	)		$—			$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2014			2013
Beginning balance, January 1		($10.2	)		($0.6	)
Total net gains (losses) (realized/unrealized) included in changes in net assets	17.0			(8.1		)
Transfers into Level 3 (a)	—			0.1
Transfers out of Level 3 (b)	—			1.0
Purchases	7.9			4.8
Sales	(0.2		)	—
Settlements	(16.0		)	(7.4		)
Ending balance, December 31		($1.5	)		($10.2	)
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		$8.9			($8.1	)

(a) 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.

(b) 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.

(c) 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) at December 31 as follows (in millions):

	Alliant Energy					IPL					WPL
	Excluding FTRs			FTRs		Excluding FTRs			FTRs		Excluding FTRs			FTRs
2014		($7.0	)		$24.9		($3.2	)		$22.6		($3.8	)		$2.3
2013	(13.9		)	18.3		(2.1		)	16.7		(11.8		)	1.6