Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

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	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$32	$32	$—	$—	$32	$44	$44	$—	$—	$44
Derivatives	176	—	146	30	176	34	—	5	29	34
Deferred proceeds	214	—	—	214	214	188	—	—	188	188
Liabilities and equity:
Derivatives	9	—	8	1	9	25	—	25	—	25
Long-term debt (incl. current maturities)	7,368	—	8,329	1	8,330	6,777	—	8,107	2	8,109

IPL	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$32	$32	$—	$—	$32	$44	$44	$—	$—	$44
Derivatives	84	—	65	19	84	29	—	3	26	29
Deferred proceeds	214	—	—	214	214	188	—	—	188	188
Liabilities and equity:
Derivatives	4	—	3	1	4	12	—	12	—	12
Long-term debt	3,643	—	4,124	—	4,124	3,345	—	4,021	—	4,021

WPL	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Derivatives	$92	$—	$81	$11	$92	$5	$—	$2	$3	$5
Liabilities and equity:
Derivatives	5	—	5	—	5	13	—	13	—	13
Long-term debt (incl. current maturities)	2,429	—	2,862	—	2,862	2,130	—	2,690	—	2,690

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
	2021	2020	2021	2020
Beginning balance, January 1	$29	$21	$188	$188
Total net gains included in changes in net assets (realized/unrealized)	6	11	—	—
Purchases	21	14	—	—
Sales	(1)	(1)	—	—
Settlements (a)	(26)	(16)	26	—
Ending balance, December 31	$29	$29	$214	$188
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	$6	$11	$—	$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2021	2020	2021	2020
Beginning balance, January 1	$26	$18	$188	$188
Total net gains (losses) included in changes in net assets (realized/unrealized)	(3)	10	—	—
Purchases	16	11	—	—
Sales	(1)	(1)	—	—
Settlements (a)	(20)	(12)	26	—
Ending balance, December 31	$18	$26	$214	$188
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	($3)	$10	$—	$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2021	2020
Beginning balance, January 1	$3	$3
Total net gains included in changes in net assets (realized/unrealized)	9	1
Purchases	5	3
Settlements	(6)	(4)
Ending balance, December 31	$11	$3
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	$9	$1

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses 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
2021	$9	$20	$8	$10	$1	$10
2020	18	11	17	9	1	2

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	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$32	$32	$—	$—	$32	$44	$44	$—	$—	$44
Derivatives	176	—	146	30	176	34	—	5	29	34
Deferred proceeds	214	—	—	214	214	188	—	—	188	188
Liabilities and equity:
Derivatives	9	—	8	1	9	25	—	25	—	25
Long-term debt (incl. current maturities)	7,368	—	8,329	1	8,330	6,777	—	8,107	2	8,109

IPL	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$32	$32	$—	$—	$32	$44	$44	$—	$—	$44
Derivatives	84	—	65	19	84	29	—	3	26	29
Deferred proceeds	214	—	—	214	214	188	—	—	188	188
Liabilities and equity:
Derivatives	4	—	3	1	4	12	—	12	—	12
Long-term debt	3,643	—	4,124	—	4,124	3,345	—	4,021	—	4,021

WPL	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Derivatives	$92	$—	$81	$11	$92	$5	$—	$2	$3	$5
Liabilities and equity:
Derivatives	5	—	5	—	5	13	—	13	—	13
Long-term debt (incl. current maturities)	2,429	—	2,862	—	2,862	2,130	—	2,690	—	2,690

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
	2021	2020	2021	2020
Beginning balance, January 1	$29	$21	$188	$188
Total net gains included in changes in net assets (realized/unrealized)	6	11	—	—
Purchases	21	14	—	—
Sales	(1)	(1)	—	—
Settlements (a)	(26)	(16)	26	—
Ending balance, December 31	$29	$29	$214	$188
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	$6	$11	$—	$—

IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2021	2020	2021	2020
Beginning balance, January 1	$26	$18	$188	$188
Total net gains (losses) included in changes in net assets (realized/unrealized)	(3)	10	—	—
Purchases	16	11	—	—
Sales	(1)	(1)	—	—
Settlements (a)	(20)	(12)	26	—
Ending balance, December 31	$18	$26	$214	$188
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	($3)	$10	$—	$—

WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2021	2020
Beginning balance, January 1	$3	$3
Total net gains included in changes in net assets (realized/unrealized)	9	1
Purchases	5	3
Settlements	(6)	(4)
Ending balance, December 31	$11	$3
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	$9	$1

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses 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
2021	$9	$20	$8	$10	$1	$10
2020	18	11	17	9	1	2

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	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$32	$32	$—	$—	$32	$44	$44	$—	$—	$44
Derivatives	176	—	146	30	176	34	—	5	29	34
Deferred proceeds	214	—	—	214	214	188	—	—	188	188
Liabilities and equity:
Derivatives	9	—	8	1	9	25	—	25	—	25
Long-term debt (incl. current maturities)	7,368	—	8,329	1	8,330	6,777	—	8,107	2	8,109

IPL	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$32	$32	$—	$—	$32	$44	$44	$—	$—	$44
Derivatives	84	—	65	19	84	29	—	3	26	29
Deferred proceeds	214	—	—	214	214	188	—	—	188	188
Liabilities and equity:
Derivatives	4	—	3	1	4	12	—	12	—	12
Long-term debt	3,643	—	4,124	—	4,124	3,345	—	4,021	—	4,021

WPL	2021					2020
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Derivatives	$92	$—	$81	$11	$92	$5	$—	$2	$3	$5
Liabilities and equity:
Derivatives	5	—	5	—	5	13	—	13	—	13
Long-term debt (incl. current maturities)	2,429	—	2,862	—	2,862	2,130	—	2,690	—	2,690

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
2021	$9	$20	$8	$10	$1	$10
2020	18	11	17	9	1	2