Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

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

Recurring Fair Value Measurements

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

Alliant Energy	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$26.8		$—		$4.8		$22.0		$26.8		$28.3		$—		$8.9		$19.4		$28.3
Deferred proceeds	187.7		—		—		187.7		187.7		119.4		—		—		119.4		119.4
Liabilities and equity:
Derivatives	37.6		—		36.8		0.8		37.6		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,190.2		—		6,917.9		2.0		6,919.9		5,502.8		—		5,858.4		2.4		5,860.8

IPL	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$22.3		$—		$2.8		$19.5		$22.3		$17.7		$—		$4.0		$13.7		$17.7
Deferred proceeds	187.7		—		—		187.7		187.7		119.4		—		—		119.4		119.4
Liabilities and equity:
Derivatives	17.4		—		16.6		0.8		17.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,147.3		—		3,489.1		—		3,489.1		2,552.3		—		2,691.2		—		2,691.2

WPL	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$4.5		$—		$2.0		$2.5		$4.5		$10.6		$—		$4.9		$5.7		$10.6
Liabilities and equity:
Derivatives	20.2		—		20.2		—		20.2		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.7		—		2,268.2		—		2,268.2		1,834.9		—		2,043.7		—		2,043.7

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
	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.2			9.1			—		—
Transfers out of Level 3 (a)	4.0			16.1			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.5		)	—		—
Settlements (b)	(16.8		)	(27.0		)	68.3		(102.7		)
Ending balance, December 31		$21.2			$12.2			$187.7		$119.4
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31		$11.4			$10.7			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)	10.7			(0.5		)	—		—
Transfers out of Level 3 (a)	2.6			11.0			—		—
Purchases	9.5			22.5			—		—
Sales	(0.1		)	(0.4		)	—		—
Settlements (b)	(13.0		)	(22.2		)	68.3		(102.7		)
Ending balance, December 31		$18.7			$9.0			$187.7		$119.4
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31		$12.6			$0.2			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(2.5		)	9.6
Transfers out of Level 3 (a)	1.4			5.1
Purchases	4.3			4.2
Sales	(0.1		)	(0.1		)
Settlements	(3.8		)	(4.8		)
Ending balance, December 31		$2.5			$3.2
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		($1.2	)		$10.5

(a) Observable market inputs became available for certain commodity contracts previously classified as Level 3 for transfers out of Level 3.

(b) 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 amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
2019		$14.6		$6.6		$13.6		$5.1		$1.0		$1.5
2018	3.2		9.0		1.8		7.2		1.4		1.8

IPL [Member]

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

Recurring Fair Value Measurements

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

Alliant Energy	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$26.8		$—		$4.8		$22.0		$26.8		$28.3		$—		$8.9		$19.4		$28.3
Deferred proceeds	187.7		—		—		187.7		187.7		119.4		—		—		119.4		119.4
Liabilities and equity:
Derivatives	37.6		—		36.8		0.8		37.6		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,190.2		—		6,917.9		2.0		6,919.9		5,502.8		—		5,858.4		2.4		5,860.8

IPL	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$22.3		$—		$2.8		$19.5		$22.3		$17.7		$—		$4.0		$13.7		$17.7
Deferred proceeds	187.7		—		—		187.7		187.7		119.4		—		—		119.4		119.4
Liabilities and equity:
Derivatives	17.4		—		16.6		0.8		17.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,147.3		—		3,489.1		—		3,489.1		2,552.3		—		2,691.2		—		2,691.2

WPL	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$4.5		$—		$2.0		$2.5		$4.5		$10.6		$—		$4.9		$5.7		$10.6
Liabilities and equity:
Derivatives	20.2		—		20.2		—		20.2		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.7		—		2,268.2		—		2,268.2		1,834.9		—		2,043.7		—		2,043.7

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
	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.2			9.1			—		—
Transfers out of Level 3 (a)	4.0			16.1			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.5		)	—		—
Settlements (b)	(16.8		)	(27.0		)	68.3		(102.7		)
Ending balance, December 31		$21.2			$12.2			$187.7		$119.4
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31		$11.4			$10.7			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)	10.7			(0.5		)	—		—
Transfers out of Level 3 (a)	2.6			11.0			—		—
Purchases	9.5			22.5			—		—
Sales	(0.1		)	(0.4		)	—		—
Settlements (b)	(13.0		)	(22.2		)	68.3		(102.7		)
Ending balance, December 31		$18.7			$9.0			$187.7		$119.4
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31		$12.6			$0.2			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(2.5		)	9.6
Transfers out of Level 3 (a)	1.4			5.1
Purchases	4.3			4.2
Sales	(0.1		)	(0.1		)
Settlements	(3.8		)	(4.8		)
Ending balance, December 31		$2.5			$3.2
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		($1.2	)		$10.5

(a) Observable market inputs became available for certain commodity contracts previously classified as Level 3 for transfers out of Level 3.

(b)

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 amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
2019		$14.6		$6.6		$13.6		$5.1		$1.0		$1.5
2018	3.2		9.0		1.8		7.2		1.4		1.8

WPL [Member]

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

Recurring Fair Value Measurements

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

Alliant Energy	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$26.8		$—		$4.8		$22.0		$26.8		$28.3		$—		$8.9		$19.4		$28.3
Deferred proceeds	187.7		—		—		187.7		187.7		119.4		—		—		119.4		119.4
Liabilities and equity:
Derivatives	37.6		—		36.8		0.8		37.6		23.3		—		16.1		7.2		23.3
Long-term debt (incl. current maturities)	6,190.2		—		6,917.9		2.0		6,919.9		5,502.8		—		5,858.4		2.4		5,860.8

IPL	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$22.3		$—		$2.8		$19.5		$22.3		$17.7		$—		$4.0		$13.7		$17.7
Deferred proceeds	187.7		—		—		187.7		187.7		119.4		—		—		119.4		119.4
Liabilities and equity:
Derivatives	17.4		—		16.6		0.8		17.4		11.2		—		6.5		4.7		11.2
Long-term debt (incl. current maturities)	3,147.3		—		3,489.1		—		3,489.1		2,552.3		—		2,691.2		—		2,691.2

WPL	2019										2018
			Fair Value										Fair Value
	Carrying		Level		Level		Level				Carrying		Level		Level		Level
	Amount		1		2		3		Total		Amount		1		2		3		Total
Assets:
Derivatives		$4.5		$—		$2.0		$2.5		$4.5		$10.6		$—		$4.9		$5.7		$10.6
Liabilities and equity:
Derivatives	20.2		—		20.2		—		20.2		12.1		—		9.6		2.5		12.1
Long-term debt (incl. current maturities)	1,932.7		—		2,268.2		—		2,268.2		1,834.9		—		2,043.7		—		2,043.7

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
	2019			2018			2019		2018
Beginning balance, January 1		$12.2			($12.2	)		$119.4		$222.1
Total net gains included in changes in net assets (realized/unrealized)	8.2			9.1			—		—
Transfers out of Level 3 (a)	4.0			16.1			—		—
Purchases	13.8			26.7			—		—
Sales	(0.2		)	(0.5		)	—		—
Settlements (b)	(16.8		)	(27.0		)	68.3		(102.7		)
Ending balance, December 31		$21.2			$12.2			$187.7		$119.4
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31		$11.4			$10.7			$—		$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net						Deferred Proceeds
	2019			2018			2019		2018
Beginning balance, January 1		$9.0			($1.4	)		$119.4		$222.1
Total net gains (losses) included in changes in net assets (realized/unrealized)	10.7			(0.5		)	—		—
Transfers out of Level 3 (a)	2.6			11.0			—		—
Purchases	9.5			22.5			—		—
Sales	(0.1		)	(0.4		)	—		—
Settlements (b)	(13.0		)	(22.2		)	68.3		(102.7		)
Ending balance, December 31		$18.7			$9.0			$187.7		$119.4
The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31		$12.6			$0.2			$—		$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2019			2018
Beginning balance, January 1		$3.2			($10.8	)
Total net gains (losses) included in changes in net assets (realized/unrealized)	(2.5		)	9.6
Transfers out of Level 3 (a)	1.4			5.1
Purchases	4.3			4.2
Sales	(0.1		)	(0.1		)
Settlements	(3.8		)	(4.8		)
Ending balance, December 31		$2.5			$3.2
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		($1.2	)		$10.5

(a) Observable market inputs became available for certain commodity contracts previously classified as Level 3 for transfers out of Level 3.

(b)

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 amounts received from the receivables sold.

Fair Value Of Net Derivative Assets (Liabilities)

The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions):

	Alliant Energy				IPL				WPL
	Excluding FTRs		FTRs		Excluding FTRs		FTRs		Excluding FTRs		FTRs
2019		$14.6		$6.6		$13.6		$5.1		$1.0		$1.5
2018	3.2		9.0		1.8		7.2		1.4		1.8