Wisconsin Power & Light 10-Q 29 Apr 22 2022 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	3 Months Ended
	Mar. 31, 2022shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity Registrant Name	ALLIANT ENERGY CORP
Entity Central Index Key	0000352541
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	1-9894
Entity Tax Identification Number	39-1380265
Title of 12(b) Security	Common Stock, $0.01 Par Value
Trading Symbol	LNT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	250,813,728
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false
IPL [Member]
Entity Information [Line Items]
Entity Registrant Name	INTERSTATE POWER & LIGHT CO
Entity Central Index Key	0000052485
Entity Incorporation, State or Country Code	IA
Entity Address, Address Line One	Alliant Energy Tower
Entity Address, City or Town	Cedar Rapids
Entity Address, State or Province	IA
Entity Address, Postal Zip Code	52401
City Area Code	319
Local Phone Number	786-4411
Entity File Number	1-4117
Entity Tax Identification Number	42-0331370
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	13,370,788
WPL [Member]
Entity Information [Line Items]
Entity Registrant Name	WISCONSIN POWER & LIGHT CO
Entity Central Index Key	0000107832
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	0-337
Entity Tax Identification Number	39-0714890
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	13,236,601

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenues:
Electric utility	$ 773	$ 701
Gas utility	262	170
Other utility	11	13
Non-utility	22	17
Total revenues	1,068	901
Operating expenses:
Electric production fuel and purchased power	168	133
Electric transmission service	138	134
Cost of gas sold	168	100
Other operation and maintenance	153	146
Depreciation and amortization	166	164
Taxes other than income taxes	27	26
Total operating expenses	820	703
Operating income	248	198
Other (income) and deductions:
Interest expense	74	69
Equity income from unconsolidated investments, net	(15)	(15)
Allowance for funds used during construction	(11)	(4)
Other	0	2
Total other (income) and deductions	48	52
Income before income taxes	200	146
Income tax expense (benefit)	8	(28)
Net income	192	174
Preferred dividend requirements of Interstate Power and Light Company	0	3
Net income attributable to common shareowners	$ 192	$ 171
Weighted average number of common shares outstanding:
Basic (in shares)	250,600	250,000
Diluted (in shares)	250,900	250,400
Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic) (in dollars per share)	$ 0.77	$ 0.68
Earnings per weighted average common share attributable to Alliant Energy common shareowners (diluted) (in dollars per share)	$ 0.77	$ 0.68
IPL [Member]
Revenues:
Electric utility	$ 400	$ 386
Gas utility	139	91
Other utility	11	12
Total revenues	550	489
Operating expenses:
Electric production fuel and purchased power	67	59
Electric transmission service	97	92
Cost of gas sold	85	50
Other operation and maintenance	83	77
Depreciation and amortization	94	94
Taxes other than income taxes	14	14
Total operating expenses	440	386
Operating income	110	103
Other (income) and deductions:
Interest expense	37	35
Allowance for funds used during construction	(3)	(2)
Total other (income) and deductions	34	33
Income before income taxes	76	70
Income tax expense (benefit)	(11)	(12)
Net income	87	82
Preferred dividend requirements of Interstate Power and Light Company	0	3
Net income attributable to common shareowners	87	79
WPL [Member]
Revenues:
Electric utility	373	315
Gas utility	123	79
Other utility	0	1
Total revenues	496	395
Operating expenses:
Electric production fuel and purchased power	101	74
Electric transmission service	41	42
Cost of gas sold	83	50
Other operation and maintenance	58	59
Depreciation and amortization	70	69
Taxes other than income taxes	12	11
Total operating expenses	365	305
Operating income	131	90
Other (income) and deductions:
Interest expense	27	26
Allowance for funds used during construction	(9)	(2)
Other	0	1
Total other (income) and deductions	18	25
Income before income taxes	113	65
Income tax expense (benefit)	21	(19)
Net income	$ 92	$ 84

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 67	$ 39
Accounts receivable, less allowance for expected credit losses	481	440
Production fuel, at weighted average cost	39	51
Gas stored underground, at weighted average cost	27	82
Materials and supplies, at weighted average cost	119	113
Regulatory assets	88	104
Other	271	240
Total current assets	1,092	1,069
Property, plant and equipment, net	15,192	14,987
Investments:
ATC Holdings	346	338
Other	187	179
Total investments	533	517
Other assets:
Regulatory assets	1,831	1,836
Deferred charges and other	191	144
Total other assets	2,022	1,980
Total assets	18,839	18,553
Current liabilities:
Current maturities of long-term debt	333	633
Commercial paper	276	515
Accounts payable	383	436
Accrued taxes	66	58
Regulatory liabilities	251	186
Other	212	226
Total current liabilities	1,521	2,054
Long-term debt, net (excluding current portion)	7,383	6,735
Other liabilities:
Deferred tax liabilities	1,958	1,927
Regulatory liabilities	1,121	1,085
Pension and other benefit obligations	363	374
Other	416	388
Total other liabilities	3,858	3,774
Commitments and contingencies (Note 12)
Common equity:
Common stock	3	3
Additional paid-in capital	2,750	2,749
Retained earnings	3,336	3,250
Shares in deferred compensation trust - 381,397 and 383,532 shares at a weighted average cost of $31.17 and $30.59 per share	(12)	(12)
Total common equity	6,077	5,990
Total liabilities and equity	18,839	18,553
IPL [Member]
Current assets:
Cash and cash equivalents	62	34
Accounts receivable, less allowance for expected credit losses	257	241
Income tax refunds receivable	25	8
Production fuel, at weighted average cost	28	29
Gas stored underground, at weighted average cost	11	40
Materials and supplies, at weighted average cost	71	70
Regulatory assets	60	73
Other	85	69
Total current assets	599	564
Property, plant and equipment, net	7,976	7,983
Other assets:
Regulatory assets	1,372	1,370
Deferred charges and other	103	79
Total other assets	1,475	1,449
Total assets	10,050	9,996
Current liabilities:
Accounts payable	135	173
Accounts payable to associated companies	46	39
Accrued taxes	57	56
Accrued interest	35	36
Regulatory liabilities	122	84
Other	62	67
Total current liabilities	457	455
Long-term debt, net (excluding current portion)	3,644	3,643
Other liabilities:
Deferred tax liabilities	1,107	1,083
Regulatory liabilities	632	607
Pension and other benefit obligations	124	127
Other	311	312
Total other liabilities	2,174	2,129
Commitments and contingencies (Note 12)
Common equity:
Common stock	33	33
Additional paid-in capital	2,807	2,807
Retained earnings	935	929
Total common equity	3,775	3,769
Total liabilities and equity	10,050	9,996
WPL [Member]
Current assets:
Cash and cash equivalents	4	2
Accounts receivable, less allowance for expected credit losses	211	188
Production fuel, at weighted average cost	11	23
Gas stored underground, at weighted average cost	16	42
Materials and supplies, at weighted average cost	45	41
Regulatory assets	28	31
Prepaid gross receipts tax	30	40
Other	102	86
Total current assets	447	453
Property, plant and equipment, net	6,747	6,538
Other assets:
Regulatory assets	459	466
Deferred charges and other	90	61
Total other assets	549	527
Total assets	7,743	7,518
Current liabilities:
Current maturities of long-term debt	250	250
Commercial paper	157	236
Accounts payable	185	190
Accounts payable to associated companies	34	39
Regulatory liabilities	129	102
Other	102	73
Total current liabilities	857	890
Long-term debt, net (excluding current portion)	2,180	2,179
Other liabilities:
Deferred tax liabilities	759	753
Regulatory liabilities	489	478
Pension and other benefit obligations	154	159
Other	253	236
Total other liabilities	1,655	1,626
Commitments and contingencies (Note 12)
Common equity:
Common stock	66	66
Additional paid-in capital	1,884	1,704
Retained earnings	1,101	1,053
Total common equity	3,051	2,823
Total liabilities and equity	$ 7,743	$ 7,518

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	250,813,728	250,474,529
Shares in deferred compensation trust (in shares)	381,397	383,532
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 31.17	$ 30.59
IPL [Member]
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	24,000,000	24,000,000
Common stock, shares outstanding (in shares)	13,370,788	13,370,788
WPL [Member]
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	18,000,000	18,000,000
Common stock, shares outstanding (in shares)	13,236,601	13,236,601

Condensed Consolidated Statem_2

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from (used for) operating activities:
Net income	$ 192	$ 174
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	166	164
Deferred tax expense (benefit) and tax credits	18	(29)
Other	(6)	4
Other changes in assets and liabilities:
Accounts receivable	(161)	(126)
Gas stored underground	55	20
Derivative assets	(85)	6
Regulatory assets	19	(4)
Accounts payable	(37)	(6)
Regulatory liabilities	92	(60)
Deferred income taxes	15	58
Other	(17)	(56)
Net cash flows from (used for) operating activities	251	145
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(307)	(214)
Other construction and acquisition expenditures	(23)	(17)
Cash receipts on sold receivables	115	209
Other	(8)	(16)
Net cash flows from (used for) investing activities	(223)	(38)
Cash flows from (used for) financing activities:
Common stock dividends	(107)	(102)
Proceeds from issuance of long-term debt	650	0
Payments to retire long-term debt	(300)	0
Net change in commercial paper	(239)	(53)
Other	(1)	10
Net cash flows from (used for) financing activities	3	(145)
Net increase (decrease) in cash, cash equivalents and restricted cash	31	(38)
Cash, cash equivalents and restricted cash at beginning of period	40	56
Cash, cash equivalents and restricted cash at end of period	71	18
Supplemental cash flows information:
Interest	(62)	(59)
Significant non-cash investing and financing activities:
Accrued capital expenditures	134	64
Beneficial interest obtained in exchange for securitized accounts receivable	227	107
IPL [Member]
Cash flows from (used for) operating activities:
Net income	87	82
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	94	94
Deferred tax expense (benefit) and tax credits	15	(2)
Other	(2)	(1)
Other changes in assets and liabilities:
Accounts receivable	(128)	(133)
Income tax refunds receivable	(17)	(3)
Gas stored underground	29	12
Derivative assets	(43)	10
Regulatory assets	9	(16)
Regulatory liabilities	59	(19)
Other	(14)	(69)
Net cash flows from (used for) operating activities	89	(45)
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(96)	(106)
Cash receipts on sold receivables	115	209
Other	(1)	(5)
Net cash flows from (used for) investing activities	18	98
Cash flows from (used for) financing activities:
Common stock dividends	(81)	(101)
Other	2	9
Net cash flows from (used for) financing activities	(79)	(92)
Net increase (decrease) in cash, cash equivalents and restricted cash	28	(39)
Cash, cash equivalents and restricted cash at beginning of period	34	50
Cash, cash equivalents and restricted cash at end of period	62	11
Supplemental cash flows information:
Interest	(37)	(37)
Income taxes, net	0	(7)
Significant non-cash investing and financing activities:
Accrued capital expenditures	27	31
Beneficial interest obtained in exchange for securitized accounts receivable	227	107
WPL [Member]
Cash flows from (used for) operating activities:
Net income	92	84
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	70	69
Deferred tax expense (benefit) and tax credits	(2)	(28)
Other	(3)	4
Other changes in assets and liabilities:
Accounts receivable	(23)	9
Gas stored underground	26	9
Derivative assets	(42)	(4)
Accounts payable	(24)	(24)
Regulatory liabilities	32	(41)
Accrued taxes	21	8
Deferred income taxes	8	44
Other	12	18
Net cash flows from (used for) operating activities	167	148
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(212)	(108)
Other	(5)	(11)
Net cash flows from (used for) investing activities	(217)	(119)
Cash flows from (used for) financing activities:
Common stock dividends	(44)	(42)
Capital contributions from parent	180	125
Net change in commercial paper	(79)	(109)
Other	(5)	(4)
Net cash flows from (used for) financing activities	52	(30)
Net increase (decrease) in cash, cash equivalents and restricted cash	2	(1)
Cash, cash equivalents and restricted cash at beginning of period	2	3
Cash, cash equivalents and restricted cash at end of period	4	2
Supplemental cash flows information:
Interest	(23)	(21)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 104	$ 32

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2021 Form 10-K . In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the three months ended March 31, 2022 are not necessarily indicative of results that may be expected for the year ending December 31, 2022. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. NOTE 1(b) Cash, Cash Equivalents and Restricted Cash - At March 31, 2022, Alliant Energy’s and IPL’s cash and cash equivalents included $59 million of money market fund investments, with an interest rate of 0.3%.
IPL [Member]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2021 Form 10-K . In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the three months ended March 31, 2022 are not necessarily indicative of results that may be expected for the year ending December 31, 2022. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. NOTE 1(b) Cash, Cash Equivalents and Restricted Cash - At March 31, 2022, Alliant Energy’s and IPL’s cash and cash equivalents included $59 million of money market fund investments, with an interest rate of 0.3%.
WPL [Member]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2021 Form 10-K . In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the results of operations, financial position and cash flows have been made. Results for the three months ended March 31, 2022 are not necessarily indicative of results that may be expected for the year ending December 31, 2022. A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

Regulatory Matters

Regulatory Matters	3 Months Ended
	Mar. 31, 2022
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $949 $934 $896 $884 $53 $50 Pension and OPEB costs 453 462 224 228 229 234 Asset retirement obligations 134 128 94 89 40 39 Assets retired early 88 92 64 66 24 26 IPL’s DAEC PPA amendment 84 90 84 90 — — WPL’s Western Wisconsin gas distribution expansion investments 50 52 — — 50 52 Commodity cost recovery 42 42 2 2 40 40 Other 119 140 68 84 51 56 $1,919 $1,940 $1,432 $1,443 $487 $497 Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $578 $585 $310 $312 $268 $273 Cost of removal obligations 391 384 256 252 135 132 Derivatives 258 166 125 77 133 89 Electric transmission cost recovery 50 51 29 27 21 24 WPL’s West Riverside liquidated damages 35 36 — — 35 36 Other 60 49 34 23 26 26 $1,372 $1,271 $754 $691 $618 $580
IPL [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $949 $934 $896 $884 $53 $50 Pension and OPEB costs 453 462 224 228 229 234 Asset retirement obligations 134 128 94 89 40 39 Assets retired early 88 92 64 66 24 26 IPL’s DAEC PPA amendment 84 90 84 90 — — WPL’s Western Wisconsin gas distribution expansion investments 50 52 — — 50 52 Commodity cost recovery 42 42 2 2 40 40 Other 119 140 68 84 51 56 $1,919 $1,940 $1,432 $1,443 $487 $497 Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $578 $585 $310 $312 $268 $273 Cost of removal obligations 391 384 256 252 135 132 Derivatives 258 166 125 77 133 89 Electric transmission cost recovery 50 51 29 27 21 24 WPL’s West Riverside liquidated damages 35 36 — — 35 36 Other 60 49 34 23 26 26 $1,372 $1,271 $754 $691 $618 $580
WPL [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $949 $934 $896 $884 $53 $50 Pension and OPEB costs 453 462 224 228 229 234 Asset retirement obligations 134 128 94 89 40 39 Assets retired early 88 92 64 66 24 26 IPL’s DAEC PPA amendment 84 90 84 90 — — WPL’s Western Wisconsin gas distribution expansion investments 50 52 — — 50 52 Commodity cost recovery 42 42 2 2 40 40 Other 119 140 68 84 51 56 $1,919 $1,940 $1,432 $1,443 $487 $497 Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $578 $585 $310 $312 $268 $273 Cost of removal obligations 391 384 256 252 135 132 Derivatives 258 166 125 77 133 89 Electric transmission cost recovery 50 51 29 27 21 24 WPL’s West Riverside liquidated damages 35 36 — — 35 36 Other 60 49 34 23 26 26 $1,372 $1,271 $754 $691 $618 $580

Receivables

Receivables	3 Months Ended
	Mar. 31, 2022
Receivables [Line Items]
Receivables	RECEIVABLES Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of March 31, 2022, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three months ended March 31 were as follows (in millions): 2022 2021 Maximum outstanding aggregate cash proceeds $36 $100 Average outstanding aggregate cash proceeds 4 30 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2022 December 31, 2021 Customer accounts receivable $142 $125 Unbilled utility revenues 96 104 Receivables sold to third party 238 229 Less: cash proceeds 1 1 Deferred proceeds 237 228 Less: allowance for expected credit losses 10 14 Fair value of deferred proceeds $227 $214 As of March 31, 2022, outstanding receivables past due under the Receivables Agreement were $24 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions): 2022 2021 Collections $561 $529 Write-offs, net of recoveries 2 2
IPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of March 31, 2022, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three months ended March 31 were as follows (in millions): 2022 2021 Maximum outstanding aggregate cash proceeds $36 $100 Average outstanding aggregate cash proceeds 4 30 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2022 December 31, 2021 Customer accounts receivable $142 $125 Unbilled utility revenues 96 104 Receivables sold to third party 238 229 Less: cash proceeds 1 1 Deferred proceeds 237 228 Less: allowance for expected credit losses 10 14 Fair value of deferred proceeds $227 $214 As of March 31, 2022, outstanding receivables past due under the Receivables Agreement were $24 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions): 2022 2021 Collections $561 $529 Write-offs, net of recoveries 2 2

Investments

Investments	3 Months Ended
	Mar. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investments	INVESTMENTS Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three months ended March 31 was as follows (in millions): 2022 2021 ATC Holdings ($11) ($11) Other (4) (4) ($15) ($15)

Common Equity

Common Equity	3 Months Ended
	Mar. 31, 2022
Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2022 250,474,529 Shareowner Direct Plan 116,431 Equity-based compensation plans 222,768 Shares outstanding, March 31, 2022 250,813,728 Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Loss Trust of IPL Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 192 192 Common stock dividends ($0.4275 per share) (107) (107) Shareowner Direct Plan issuances 7 7 Equity-based compensation plans and other (6) 1 (5) Ending balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $2 $2,704 $2,994 ($1) ($11) $200 $5,888 Net income attributable to Alliant Energy common shareowners 171 171 Common stock dividends ($0.4025 per share) (102) (102) Shareowner Direct Plan issuances 1 7 8 Equity-based compensation plans and other 1 1 Ending balance, March 31, 2021 $3 $2,712 $3,063 ($1) ($11) $200 $5,966 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $— $3,769 Net income available for common stock 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $— $3,775 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $33 $2,752 $979 $200 $3,964 Net income available for common stock 79 79 Common stock dividends (101) (101) Ending balance, March 31, 2021 $33 $2,752 $957 $200 $3,942 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $2,823 Net income 92 92 Common stock dividends (44) (44) Capital contributions from parent 180 180 Ending balance, March 31, 2022 $66 $1,884 $1,101 $3,051 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $66 $1,459 $953 $2,478 Net income 84 84 Common stock dividends (42) (42) Capital contributions from parent 125 125 Ending balance, March 31, 2021 $66 $1,584 $995 $2,645
IPL [Member]
Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2022 250,474,529 Shareowner Direct Plan 116,431 Equity-based compensation plans 222,768 Shares outstanding, March 31, 2022 250,813,728 Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Loss Trust of IPL Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 192 192 Common stock dividends ($0.4275 per share) (107) (107) Shareowner Direct Plan issuances 7 7 Equity-based compensation plans and other (6) 1 (5) Ending balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $2 $2,704 $2,994 ($1) ($11) $200 $5,888 Net income attributable to Alliant Energy common shareowners 171 171 Common stock dividends ($0.4025 per share) (102) (102) Shareowner Direct Plan issuances 1 7 8 Equity-based compensation plans and other 1 1 Ending balance, March 31, 2021 $3 $2,712 $3,063 ($1) ($11) $200 $5,966 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $— $3,769 Net income available for common stock 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $— $3,775 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $33 $2,752 $979 $200 $3,964 Net income available for common stock 79 79 Common stock dividends (101) (101) Ending balance, March 31, 2021 $33 $2,752 $957 $200 $3,942 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $2,823 Net income 92 92 Common stock dividends (44) (44) Capital contributions from parent 180 180 Ending balance, March 31, 2022 $66 $1,884 $1,101 $3,051 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $66 $1,459 $953 $2,478 Net income 84 84 Common stock dividends (42) (42) Capital contributions from parent 125 125 Ending balance, March 31, 2021 $66 $1,584 $995 $2,645
WPL [Member]
Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2022 250,474,529 Shareowner Direct Plan 116,431 Equity-based compensation plans 222,768 Shares outstanding, March 31, 2022 250,813,728 Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Loss Trust of IPL Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 192 192 Common stock dividends ($0.4275 per share) (107) (107) Shareowner Direct Plan issuances 7 7 Equity-based compensation plans and other (6) 1 (5) Ending balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $2 $2,704 $2,994 ($1) ($11) $200 $5,888 Net income attributable to Alliant Energy common shareowners 171 171 Common stock dividends ($0.4025 per share) (102) (102) Shareowner Direct Plan issuances 1 7 8 Equity-based compensation plans and other 1 1 Ending balance, March 31, 2021 $3 $2,712 $3,063 ($1) ($11) $200 $5,966 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $— $3,769 Net income available for common stock 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $— $3,775 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $33 $2,752 $979 $200 $3,964 Net income available for common stock 79 79 Common stock dividends (101) (101) Ending balance, March 31, 2021 $33 $2,752 $957 $200 $3,942 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $2,823 Net income 92 92 Common stock dividends (44) (44) Capital contributions from parent 180 180 Ending balance, March 31, 2022 $66 $1,884 $1,101 $3,051 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $66 $1,459 $953 $2,478 Net income 84 84 Common stock dividends (42) (42) Capital contributions from parent 125 125 Ending balance, March 31, 2021 $66 $1,584 $995 $2,645

Debt

Debt	3 Months Ended
	Mar. 31, 2022
Debt [Line Items]
Debt	DEBT NOTE 6(a) Short-term Debt - Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions): March 31, 2022 Alliant Energy IPL WPL Amount outstanding $276 $— $157 Weighted average interest rates 0.6% N/A 0.5% Available credit facility capacity $724 $250 $143 Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $577 $578 $— $— $252 $275 Average amount outstanding (based on daily outstanding balances) $443 $424 $— $— $205 $189 Weighted average interest rates 0.3% 0.2% —% —% 0.3% 0.2% NOTE 6(b) Long-term Debt - In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In March 2022, AEF entered into a $300 million variable rate (1% as of March 31, 2022) term loan credit agreement (with Alliant Energy as guarantor), which expires in March 2024, and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022.
IPL [Member]
Debt [Line Items]
Debt	DEBT NOTE 6(a) Short-term Debt - Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions): March 31, 2022 Alliant Energy IPL WPL Amount outstanding $276 $— $157 Weighted average interest rates 0.6% N/A 0.5% Available credit facility capacity $724 $250 $143 Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $577 $578 $— $— $252 $275 Average amount outstanding (based on daily outstanding balances) $443 $424 $— $— $205 $189 Weighted average interest rates 0.3% 0.2% —% —% 0.3% 0.2%
WPL [Member]
Debt [Line Items]
Debt	DEBT NOTE 6(a) Short-term Debt - Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions): March 31, 2022 Alliant Energy IPL WPL Amount outstanding $276 $— $157 Weighted average interest rates 0.6% N/A 0.5% Available credit facility capacity $724 $250 $143 Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $577 $578 $— $— $252 $275 Average amount outstanding (based on daily outstanding balances) $443 $424 $— $— $205 $189 Weighted average interest rates 0.3% 0.2% —% —% 0.3% 0.2%

Revenues

Revenues	3 Months Ended
	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	REVENUES Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Electric Utility: Retail - residential $293 $262 $150 $139 $143 $123 Retail - commercial 188 172 118 110 70 62 Retail - industrial 211 202 111 112 100 90 Wholesale 47 40 15 11 32 29 Bulk power and other 34 25 6 14 28 11 Total Electric Utility 773 701 400 386 373 315 Gas Utility: Retail - residential 158 99 85 52 73 47 Retail - commercial 82 53 40 27 42 26 Retail - industrial 8 5 5 3 3 2 Transportation/other 14 13 9 9 5 4 Total Gas Utility 262 170 139 91 123 79 Other Utility: Steam 9 9 9 9 — — Other utility 2 4 2 3 — 1 Total Other Utility 11 13 11 12 — 1 Non-Utility and Other: Travero and other 22 17 — — — — Total Non-Utility and Other 22 17 — — — — Total revenues $1,068 $901 $550 $489 $496 $395
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	REVENUES Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Electric Utility: Retail - residential $293 $262 $150 $139 $143 $123 Retail - commercial 188 172 118 110 70 62 Retail - industrial 211 202 111 112 100 90 Wholesale 47 40 15 11 32 29 Bulk power and other 34 25 6 14 28 11 Total Electric Utility 773 701 400 386 373 315 Gas Utility: Retail - residential 158 99 85 52 73 47 Retail - commercial 82 53 40 27 42 26 Retail - industrial 8 5 5 3 3 2 Transportation/other 14 13 9 9 5 4 Total Gas Utility 262 170 139 91 123 79 Other Utility: Steam 9 9 9 9 — — Other utility 2 4 2 3 — 1 Total Other Utility 11 13 11 12 — 1 Non-Utility and Other: Travero and other 22 17 — — — — Total Non-Utility and Other 22 17 — — — — Total revenues $1,068 $901 $550 $489 $496 $395
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	REVENUES Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Electric Utility: Retail - residential $293 $262 $150 $139 $143 $123 Retail - commercial 188 172 118 110 70 62 Retail - industrial 211 202 111 112 100 90 Wholesale 47 40 15 11 32 29 Bulk power and other 34 25 6 14 28 11 Total Electric Utility 773 701 400 386 373 315 Gas Utility: Retail - residential 158 99 85 52 73 47 Retail - commercial 82 53 40 27 42 26 Retail - industrial 8 5 5 3 3 2 Transportation/other 14 13 9 9 5 4 Total Gas Utility 262 170 139 91 123 79 Other Utility: Steam 9 9 9 9 — — Other utility 2 4 2 3 — 1 Total Other Utility 11 13 11 12 — 1 Non-Utility and Other: Travero and other 22 17 — — — — Total Non-Utility and Other 22 17 — — — — Total revenues $1,068 $901 $550 $489 $496 $395

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2022
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL. Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Overall income tax rate 4% (19%) (14%) (17%) 19% (29%) Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $94 $87 $1 State net operating losses 2022-2042 578 13 2 Federal tax credits 2022-2042 589 369 197 Iowa Tax Reform - In March 2022, Iowa tax reform was enacted, which would reduce the current 9.8% Iowa corporate income tax rate beginning in 2023 if certain state income tax revenue triggers are satisfied. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year. Rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%. Alliant Energy is currently unable to predict with certainty the timing or amount of any rate reductions. The majority of any reduction in income tax expense as a result of the lower Iowa corporate income tax rate is currently expected to reduce rates for IPL’s customers. In addition, after the 2023 corporate income tax rate is known in the fourth quarter of 2022, Alliant Energy currently expects to record a charge related to the remeasurement of accumulated deferred income tax assets at its non-utility businesses.
IPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL. Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Overall income tax rate 4% (19%) (14%) (17%) 19% (29%) Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $94 $87 $1 State net operating losses 2022-2042 578 13 2 Federal tax credits 2022-2042 589 369 197 Iowa Tax Reform - In March 2022, Iowa tax reform was enacted, which would reduce the current 9.8% Iowa corporate income tax rate beginning in 2023 if certain state income tax revenue triggers are satisfied. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year. Rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%. Alliant Energy is currently unable to predict with certainty the timing or amount of any rate reductions. The majority of any reduction in income tax expense as a result of the lower Iowa corporate income tax rate is currently expected to reduce rates for IPL’s customers. In addition, after the 2023 corporate income tax rate is known in the fourth quarter of 2022, Alliant Energy currently expects to record a charge related to the remeasurement of accumulated deferred income tax assets at its non-utility businesses.
WPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL. Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Overall income tax rate 4% (19%) (14%) (17%) 19% (29%) Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $94 $87 $1 State net operating losses 2022-2042 578 13 2 Federal tax credits 2022-2042 589 369 197 Iowa Tax Reform - In March 2022, Iowa tax reform was enacted, which would reduce the current 9.8% Iowa corporate income tax rate beginning in 2023 if certain state income tax revenue triggers are satisfied. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year. Rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%. Alliant Energy is currently unable to predict with certainty the timing or amount of any rate reductions. The majority of any reduction in income tax expense as a result of the lower Iowa corporate income tax rate is currently expected to reduce rates for IPL’s customers. In addition, after the 2023 corporate income tax rate is known in the fourth quarter of 2022, Alliant Energy currently expects to record a charge related to the remeasurement of accumulated deferred income tax assets at its non-utility businesses.

Benefit Plans

Benefit Plans	3 Months Ended
	Mar. 31, 2022
Benefit Plans	BENEFIT PLANS NOTE 9(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Service cost $2 $3 $1 $1 Interest cost 9 8 1 1 Expected return on plan assets (17) (17) (1) (1) Amortization of actuarial loss 8 10 1 1 $2 $4 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Service cost $2 $2 $— $— Interest cost 4 4 1 1 Expected return on plan assets (8) (8) (1) (1) Amortization of actuarial loss 3 4 — — $1 $2 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Service cost $1 $1 $— $— Interest cost 4 4 1 — Expected return on plan assets (8) (8) — — Amortization of actuarial loss 4 5 — 1 $1 $2 $1 $1 NOTE 9(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Compensation expense $4 $3 $2 $1 $2 $1 Income tax benefits 1 1 1 — — — As of March 31, 2022, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $15 million, $8 million and $6 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the three months ended March 31, 2022, performance shares, performance restricted stock units and restricted stock units were granted to key employees as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards. Weighted Average Grants Grant Date Fair Value Performance shares 70,240 $54.45 Performance restricted stock units 80,252 56.62 Restricted stock units 74,360 56.62 As of March 31, 2022, 322,288 shares were included in the calculation of diluted EPS related to the nonvested equity awards.
IPL [Member]
Benefit Plans	BENEFIT PLANS NOTE 9(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Service cost $2 $3 $1 $1 Interest cost 9 8 1 1 Expected return on plan assets (17) (17) (1) (1) Amortization of actuarial loss 8 10 1 1 $2 $4 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Service cost $2 $2 $— $— Interest cost 4 4 1 1 Expected return on plan assets (8) (8) (1) (1) Amortization of actuarial loss 3 4 — — $1 $2 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Service cost $1 $1 $— $— Interest cost 4 4 1 — Expected return on plan assets (8) (8) — — Amortization of actuarial loss 4 5 — 1 $1 $2 $1 $1 NOTE 9(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Compensation expense $4 $3 $2 $1 $2 $1 Income tax benefits 1 1 1 — — — As of March 31, 2022, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $15 million, $8 million and $6 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the three months ended March 31, 2022, performance shares, performance restricted stock units and restricted stock units were granted to key employees as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards. Weighted Average Grants Grant Date Fair Value Performance shares 70,240 $54.45 Performance restricted stock units 80,252 56.62 Restricted stock units 74,360 56.62 As of March 31, 2022, 322,288 shares were included in the calculation of diluted EPS related to the nonvested equity awards.
WPL [Member]
Benefit Plans	BENEFIT PLANS NOTE 9(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Service cost $2 $3 $1 $1 Interest cost 9 8 1 1 Expected return on plan assets (17) (17) (1) (1) Amortization of actuarial loss 8 10 1 1 $2 $4 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Service cost $2 $2 $— $— Interest cost 4 4 1 1 Expected return on plan assets (8) (8) (1) (1) Amortization of actuarial loss 3 4 — — $1 $2 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Service cost $1 $1 $— $— Interest cost 4 4 1 — Expected return on plan assets (8) (8) — — Amortization of actuarial loss 4 5 — 1 $1 $2 $1 $1 NOTE 9(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Compensation expense $4 $3 $2 $1 $2 $1 Income tax benefits 1 1 1 — — — As of March 31, 2022, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $15 million, $8 million and $6 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the three months ended March 31, 2022, performance shares, performance restricted stock units and restricted stock units were granted to key employees as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards. Weighted Average Grants Grant Date Fair Value Performance shares 70,240 $54.45 Performance restricted stock units 80,252 56.62 Restricted stock units 74,360 56.62 As of March 31, 2022, 322,288 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2022
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 3,304 2022 175,658 2022-2030 2,653 2022-2023 2,268 2022 IPL 784 2022 94,175 2022-2030 1,053 2022-2023 — — WPL 2,520 2022 81,483 2022-2030 1,600 2022-2023 2,268 2022 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Current derivative assets $151 $113 $68 $48 $83 $65 Non-current derivative assets 110 63 59 36 51 27 Current derivative liabilities 6 8 3 4 3 4 Non-current derivative liabilities 1 1 1 — — 1 During the three months ended March 31, 2022, Alliant Energy’s, IPL’s and WPL’s derivative assets increased primarily as a result of higher natural gas prices. Based on IPL’s and WPL’s natural gas cost recovery mechanisms, this resulted in corresponding increases in derivative regulatory liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2022 and December 31, 2021, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at March 31, 2022 and December 31, 2021. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
IPL [Member]
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 3,304 2022 175,658 2022-2030 2,653 2022-2023 2,268 2022 IPL 784 2022 94,175 2022-2030 1,053 2022-2023 — — WPL 2,520 2022 81,483 2022-2030 1,600 2022-2023 2,268 2022 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Current derivative assets $151 $113 $68 $48 $83 $65 Non-current derivative assets 110 63 59 36 51 27 Current derivative liabilities 6 8 3 4 3 4 Non-current derivative liabilities 1 1 1 — — 1 During the three months ended March 31, 2022, Alliant Energy’s, IPL’s and WPL’s derivative assets increased primarily as a result of higher natural gas prices. Based on IPL’s and WPL’s natural gas cost recovery mechanisms, this resulted in corresponding increases in derivative regulatory liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2022 and December 31, 2021, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at March 31, 2022 and December 31, 2021. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
WPL [Member]
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 3,304 2022 175,658 2022-2030 2,653 2022-2023 2,268 2022 IPL 784 2022 94,175 2022-2030 1,053 2022-2023 — — WPL 2,520 2022 81,483 2022-2030 1,600 2022-2023 2,268 2022 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Current derivative assets $151 $113 $68 $48 $83 $65 Non-current derivative assets 110 63 59 36 51 27 Current derivative liabilities 6 8 3 4 3 4 Non-current derivative liabilities 1 1 1 — — 1 During the three months ended March 31, 2022, Alliant Energy’s, IPL’s and WPL’s derivative assets increased primarily as a result of higher natural gas prices. Based on IPL’s and WPL’s natural gas cost recovery mechanisms, this resulted in corresponding increases in derivative regulatory liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2022 and December 31, 2021, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at March 31, 2022 and December 31, 2021. Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 261 — 251 10 261 176 — 146 30 176 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 7 — 7 — 7 9 — 8 1 9 Long-term debt (incl. current maturities) 7,716 — 7,971 1 7,972 7,368 — 8,329 1 8,330 IPL March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 127 — 120 7 127 84 — 65 19 84 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 4 — 4 — 4 4 — 3 1 4 Long-term debt 3,644 — 3,738 — 3,738 3,643 — 4,124 — 4,124 WPL March 31, 2022 December 31, 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $134 $— $131 $3 $134 $92 $— $81 $11 $92 Liabilities: Derivatives 3 — 3 — 3 5 — 5 — 5 Long-term debt (incl. current maturities) 2,430 — 2,592 — 2,592 2,429 — 2,862 — 2,862 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 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (6) (6) — — Settlements (a) (13) (7) 13 (81) Ending balance, March 31 $10 $16 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($5) ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (4) (5) — — Settlements (a) (7) (6) 13 (81) Ending balance, March 31 $7 $15 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($4) ($6) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2022 2021 Beginning balance, January 1 $11 $3 Total net losses included in changes in net assets (realized/unrealized) (2) (1) Settlements (6) (1) Ending balance, March 31 $3 $1 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($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. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2022 $3 $7 $3 $4 $— $3 December 31, 2021 9 20 8 10 1 10
IPL [Member]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 261 — 251 10 261 176 — 146 30 176 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 7 — 7 — 7 9 — 8 1 9 Long-term debt (incl. current maturities) 7,716 — 7,971 1 7,972 7,368 — 8,329 1 8,330 IPL March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 127 — 120 7 127 84 — 65 19 84 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 4 — 4 — 4 4 — 3 1 4 Long-term debt 3,644 — 3,738 — 3,738 3,643 — 4,124 — 4,124 WPL March 31, 2022 December 31, 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $134 $— $131 $3 $134 $92 $— $81 $11 $92 Liabilities: Derivatives 3 — 3 — 3 5 — 5 — 5 Long-term debt (incl. current maturities) 2,430 — 2,592 — 2,592 2,429 — 2,862 — 2,862 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 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (6) (6) — — Settlements (a) (13) (7) 13 (81) Ending balance, March 31 $10 $16 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($5) ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (4) (5) — — Settlements (a) (7) (6) 13 (81) Ending balance, March 31 $7 $15 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($4) ($6) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2022 2021 Beginning balance, January 1 $11 $3 Total net losses included in changes in net assets (realized/unrealized) (2) (1) Settlements (6) (1) Ending balance, March 31 $3 $1 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($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. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2022 $3 $7 $3 $4 $— $3 December 31, 2021 9 20 8 10 1 10
WPL [Member]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 261 — 251 10 261 176 — 146 30 176 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 7 — 7 — 7 9 — 8 1 9 Long-term debt (incl. current maturities) 7,716 — 7,971 1 7,972 7,368 — 8,329 1 8,330 IPL March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 127 — 120 7 127 84 — 65 19 84 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 4 — 4 — 4 4 — 3 1 4 Long-term debt 3,644 — 3,738 — 3,738 3,643 — 4,124 — 4,124 WPL March 31, 2022 December 31, 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $134 $— $131 $3 $134 $92 $— $81 $11 $92 Liabilities: Derivatives 3 — 3 — 3 5 — 5 — 5 Long-term debt (incl. current maturities) 2,430 — 2,592 — 2,592 2,429 — 2,862 — 2,862 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 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (6) (6) — — Settlements (a) (13) (7) 13 (81) Ending balance, March 31 $10 $16 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($5) ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (4) (5) — — Settlements (a) (7) (6) 13 (81) Ending balance, March 31 $7 $15 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($4) ($6) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2022 2021 Beginning balance, January 1 $11 $3 Total net losses included in changes in net assets (realized/unrealized) (2) (1) Settlements (6) (1) Ending balance, March 31 $3 $1 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($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. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2022 $3 $7 $3 $4 $— $3 December 31, 2021 9 20 8 10 1 10

Commitments And Contingencies

Commitments And Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 12(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including WPL’s expansion of solar generation. At March 31, 2022, Alliant Energy’s and WPL’s minimum future commitments for these projects were $214 million and $213 million, respectively. NOTE 12(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At March 31, 2022, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $939 $472 $467 Coal 127 72 55 Other (a) 135 66 36 $1,201 $610 $558 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2022. NOTE 12(c) Guarantees and Indemnifications - Whiting Petroleum - Whiting Petroleum is an independent oil and gas company. In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations. As of March 31, 2022, the currently known partnership obligations for the abandonment obligations are estimated at $60 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy estimates its expected loss to be a portion of the $60 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners. Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay; however, as of both March 31, 2022 and December 31, 2021, a liability of $5 million is recorded in “Other liabilities” on Alliant Energy’s balance sheets for expected credit losses related to the contingent obligations that are in the scope of these guarantees. Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $67 million as of March 31, 2022 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of March 31, 2022 and December 31, 2021. NOTE 12(d) Environmental Matters - Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At March 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At March 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $10 - $26 $7 - $20 Current and non-current environmental liabilities $12 $9 IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers. Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act. NOTE 12(e) Collective Bargaining Agreements - At March 31, 2022, employees covered by collective bargaining agreements represented 55%, 70% and 83% of total employees of Alliant Energy, IPL and WPL, respectively. In May 2022, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expires, representing 26% and 83% of total employees of Alliant Energy and WPL, respectively. While the process to renew the agreement is underway and a tentative agreement has been reached, Alliant Energy and WPL are currently unable to predict the outcome.
IPL [Member]
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 12(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including WPL’s expansion of solar generation. At March 31, 2022, Alliant Energy’s and WPL’s minimum future commitments for these projects were $214 million and $213 million, respectively. NOTE 12(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At March 31, 2022, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $939 $472 $467 Coal 127 72 55 Other (a) 135 66 36 $1,201 $610 $558 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2022. NOTE 12(c) Guarantees and Indemnifications - Whiting Petroleum - Whiting Petroleum is an independent oil and gas company. In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations. As of March 31, 2022, the currently known partnership obligations for the abandonment obligations are estimated at $60 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy estimates its expected loss to be a portion of the $60 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners. Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay; however, as of both March 31, 2022 and December 31, 2021, a liability of $5 million is recorded in “Other liabilities” on Alliant Energy’s balance sheets for expected credit losses related to the contingent obligations that are in the scope of these guarantees. Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $67 million as of March 31, 2022 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of March 31, 2022 and December 31, 2021. NOTE 12(d) Environmental Matters - Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At March 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At March 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $10 - $26 $7 - $20 Current and non-current environmental liabilities $12 $9 IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers. Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act. NOTE 12(e) Collective Bargaining Agreements - At March 31, 2022, employees covered by collective bargaining agreements represented 55%, 70% and 83% of total employees of Alliant Energy, IPL and WPL, respectively. In May 2022, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expires, representing 26% and 83% of total employees of Alliant Energy and WPL, respectively. While the process to renew the agreement is underway and a tentative agreement has been reached, Alliant Energy and WPL are currently unable to predict the outcome.
WPL [Member]
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 12(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including WPL’s expansion of solar generation. At March 31, 2022, Alliant Energy’s and WPL’s minimum future commitments for these projects were $214 million and $213 million, respectively. NOTE 12(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At March 31, 2022, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $939 $472 $467 Coal 127 72 55 Other (a) 135 66 36 $1,201 $610 $558 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2022. NOTE 12(c) Guarantees and Indemnifications - Whiting Petroleum - Whiting Petroleum is an independent oil and gas company. In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations. As of March 31, 2022, the currently known partnership obligations for the abandonment obligations are estimated at $60 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy estimates its expected loss to be a portion of the $60 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners. Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay; however, as of both March 31, 2022 and December 31, 2021, a liability of $5 million is recorded in “Other liabilities” on Alliant Energy’s balance sheets for expected credit losses related to the contingent obligations that are in the scope of these guarantees. Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $67 million as of March 31, 2022 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of March 31, 2022 and December 31, 2021. NOTE 12(d) Environmental Matters - Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At March 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At March 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $10 - $26 $7 - $20 Current and non-current environmental liabilities $12 $9 IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers. Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act. NOTE 12(e) Collective Bargaining Agreements - At March 31, 2022, employees covered by collective bargaining agreements represented 55%, 70% and 83% of total employees of Alliant Energy, IPL and WPL, respectively. In May 2022, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expires, representing 26% and 83% of total employees of Alliant Energy and WPL, respectively. While the process to renew the agreement is underway and a tentative agreement has been reached, Alliant Energy and WPL are currently unable to predict the outcome.

Segments Of Business

Segments Of Business	3 Months Ended
	Mar. 31, 2022
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations. Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2022 Revenues $773 $262 $11 $1,046 $22 $1,068 Operating income 181 57 3 241 7 248 Net income attributable to Alliant Energy common shareowners 179 13 192 Three Months Ended March 31, 2021 Revenues $701 $170 $13 $884 $17 $901 Operating income 147 44 2 193 5 198 Net income attributable to Alliant Energy common shareowners 163 8 171 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income available for common stock 87 Three Months Ended March 31, 2021 Revenues $386 $91 $12 $489 Operating income 72 30 1 103 Net income available for common stock 79 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92 Three Months Ended March 31, 2021 Revenues $315 $79 $1 $395 Operating income 75 14 1 90 Net income 84
IPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations. Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2022 Revenues $773 $262 $11 $1,046 $22 $1,068 Operating income 181 57 3 241 7 248 Net income attributable to Alliant Energy common shareowners 179 13 192 Three Months Ended March 31, 2021 Revenues $701 $170 $13 $884 $17 $901 Operating income 147 44 2 193 5 198 Net income attributable to Alliant Energy common shareowners 163 8 171 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income available for common stock 87 Three Months Ended March 31, 2021 Revenues $386 $91 $12 $489 Operating income 72 30 1 103 Net income available for common stock 79 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92 Three Months Ended March 31, 2021 Revenues $315 $79 $1 $395 Operating income 75 14 1 90 Net income 84
WPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations. Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2022 Revenues $773 $262 $11 $1,046 $22 $1,068 Operating income 181 57 3 241 7 248 Net income attributable to Alliant Energy common shareowners 179 13 192 Three Months Ended March 31, 2021 Revenues $701 $170 $13 $884 $17 $901 Operating income 147 44 2 193 5 198 Net income attributable to Alliant Energy common shareowners 163 8 171 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income available for common stock 87 Three Months Ended March 31, 2021 Revenues $386 $91 $12 $489 Operating income 72 30 1 103 Net income available for common stock 79 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92 Three Months Ended March 31, 2021 Revenues $315 $79 $1 $395 Operating income 75 14 1 90 Net income 84

Related Parties

Related Parties	3 Months Ended
	Mar. 31, 2022
Related Party Transactions [Line Items]
Related Parties	RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions): IPL WPL 2022 2021 2022 2021 Corporate Services billings $40 $40 $36 $35 Sales credited — 1 18 1 Purchases billed 94 143 22 26 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2022 December 31, 2021 March 31, 2022 December 31, 2021 Net payables to Corporate Services $120 $110 $76 $83 ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three months ended March 31 were as follows (in millions): 2022 2021 ATC billings to WPL $34 $32 WPL billings to ATC 3 3 WPL owed ATC net amounts of $9 million as of March 31, 2022 and $10 million as of December 31, 2021.
IPL [Member]
Related Party Transactions [Line Items]
Related Parties	RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions): IPL WPL 2022 2021 2022 2021 Corporate Services billings $40 $40 $36 $35 Sales credited — 1 18 1 Purchases billed 94 143 22 26 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2022 December 31, 2021 March 31, 2022 December 31, 2021 Net payables to Corporate Services $120 $110 $76 $83
WPL [Member]
Related Party Transactions [Line Items]
Related Parties	RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions): IPL WPL 2022 2021 2022 2021 Corporate Services billings $40 $40 $36 $35 Sales credited — 1 18 1 Purchases billed 94 143 22 26 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2022 December 31, 2021 March 31, 2022 December 31, 2021 Net payables to Corporate Services $120 $110 $76 $83 ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three months ended March 31 were as follows (in millions): 2022 2021 ATC billings to WPL $34 $32 WPL billings to ATC 3 3 WPL owed ATC net amounts of $9 million as of March 31, 2022 and $10 million as of December 31, 2021.

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2022
General, Basis of Accounting	The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2021 Form 10-K .
General, Use of Estimates	A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred.
General, Reclassification	Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.
Cash, Cash Equivalents and Restricted Cash	At March 31, 2022, Alliant Energy’s and IPL’s cash and cash equivalents included $59 million of money market fund investments, with an interest rate of 0.3%.
IPL [Member]
General, Basis of Accounting	The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2021 Form 10-K .
General, Use of Estimates	A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred.
General, Reclassification	Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.
Cash, Cash Equivalents and Restricted Cash	At March 31, 2022, Alliant Energy’s and IPL’s cash and cash equivalents included $59 million of money market fund investments, with an interest rate of 0.3%.
WPL [Member]
General, Basis of Accounting	The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2021 Form 10-K .
General, Use of Estimates	A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred.
General, Reclassification	Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2022
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $949 $934 $896 $884 $53 $50 Pension and OPEB costs 453 462 224 228 229 234 Asset retirement obligations 134 128 94 89 40 39 Assets retired early 88 92 64 66 24 26 IPL’s DAEC PPA amendment 84 90 84 90 — — WPL’s Western Wisconsin gas distribution expansion investments 50 52 — — 50 52 Commodity cost recovery 42 42 2 2 40 40 Other 119 140 68 84 51 56 $1,919 $1,940 $1,432 $1,443 $487 $497
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $578 $585 $310 $312 $268 $273 Cost of removal obligations 391 384 256 252 135 132 Derivatives 258 166 125 77 133 89 Electric transmission cost recovery 50 51 29 27 21 24 WPL’s West Riverside liquidated damages 35 36 — — 35 36 Other 60 49 34 23 26 26 $1,372 $1,271 $754 $691 $618 $580
IPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $949 $934 $896 $884 $53 $50 Pension and OPEB costs 453 462 224 228 229 234 Asset retirement obligations 134 128 94 89 40 39 Assets retired early 88 92 64 66 24 26 IPL’s DAEC PPA amendment 84 90 84 90 — — WPL’s Western Wisconsin gas distribution expansion investments 50 52 — — 50 52 Commodity cost recovery 42 42 2 2 40 40 Other 119 140 68 84 51 56 $1,919 $1,940 $1,432 $1,443 $487 $497
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $578 $585 $310 $312 $268 $273 Cost of removal obligations 391 384 256 252 135 132 Derivatives 258 166 125 77 133 89 Electric transmission cost recovery 50 51 29 27 21 24 WPL’s West Riverside liquidated damages 35 36 — — 35 36 Other 60 49 34 23 26 26 $1,372 $1,271 $754 $691 $618 $580
WPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $949 $934 $896 $884 $53 $50 Pension and OPEB costs 453 462 224 228 229 234 Asset retirement obligations 134 128 94 89 40 39 Assets retired early 88 92 64 66 24 26 IPL’s DAEC PPA amendment 84 90 84 90 — — WPL’s Western Wisconsin gas distribution expansion investments 50 52 — — 50 52 Commodity cost recovery 42 42 2 2 40 40 Other 119 140 68 84 51 56 $1,919 $1,940 $1,432 $1,443 $487 $497
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Tax-related $578 $585 $310 $312 $268 $273 Cost of removal obligations 391 384 256 252 135 132 Derivatives 258 166 125 77 133 89 Electric transmission cost recovery 50 51 29 27 21 24 WPL’s West Riverside liquidated damages 35 36 — — 35 36 Other 60 49 34 23 26 26 $1,372 $1,271 $754 $691 $618 $580

Receivables (Tables)

Receivables (Tables)	3 Months Ended
	Mar. 31, 2022
Receivables [Line Items]
Maximum And Average Outstanding Cash Proceeds	IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three months ended March 31 were as follows (in millions): 2022 2021 Maximum outstanding aggregate cash proceeds $36 $100 Average outstanding aggregate cash proceeds 4 30
Attributes of Receivables Sold Under the Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2022 December 31, 2021 Customer accounts receivable $142 $125 Unbilled utility revenues 96 104 Receivables sold to third party 238 229 Less: cash proceeds 1 1 Deferred proceeds 237 228 Less: allowance for expected credit losses 10 14 Fair value of deferred proceeds $227 $214
Additional Attributes Of Receivables Sold Under The Receivables Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions): 2022 2021 Collections $561 $529 Write-offs, net of recoveries 2 2
IPL [Member]
Receivables [Line Items]
Maximum And Average Outstanding Cash Proceeds	IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three months ended March 31 were as follows (in millions): 2022 2021 Maximum outstanding aggregate cash proceeds $36 $100 Average outstanding aggregate cash proceeds 4 30
Attributes of Receivables Sold Under the Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2022 December 31, 2021 Customer accounts receivable $142 $125 Unbilled utility revenues 96 104 Receivables sold to third party 238 229 Less: cash proceeds 1 1 Deferred proceeds 237 228 Less: allowance for expected credit losses 10 14 Fair value of deferred proceeds $227 $214
Additional Attributes Of Receivables Sold Under The Receivables Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions): 2022 2021 Collections $561 $529 Write-offs, net of recoveries 2 2

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2022
Schedule of Equity Method Investments [Line Items]
Unconsolidated Equity Investments	Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three months ended March 31 was as follows (in millions): 2022 2021 ATC Holdings ($11) ($11) Other (4) (4) ($15) ($15)

Common Equity (Tables)

Common Equity (Tables)	3 Months Ended
	Mar. 31, 2022
Schedule of Capitalization, Equity [Line Items]
Common Share Activity	A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2022 250,474,529 Shareowner Direct Plan 116,431 Equity-based compensation plans 222,768 Shares outstanding, March 31, 2022 250,813,728
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Loss Trust of IPL Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 192 192 Common stock dividends ($0.4275 per share) (107) (107) Shareowner Direct Plan issuances 7 7 Equity-based compensation plans and other (6) 1 (5) Ending balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $2 $2,704 $2,994 ($1) ($11) $200 $5,888 Net income attributable to Alliant Energy common shareowners 171 171 Common stock dividends ($0.4025 per share) (102) (102) Shareowner Direct Plan issuances 1 7 8 Equity-based compensation plans and other 1 1 Ending balance, March 31, 2021 $3 $2,712 $3,063 ($1) ($11) $200 $5,966 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $— $3,769 Net income available for common stock 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $— $3,775 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $33 $2,752 $979 $200 $3,964 Net income available for common stock 79 79 Common stock dividends (101) (101) Ending balance, March 31, 2021 $33 $2,752 $957 $200 $3,942 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $2,823 Net income 92 92 Common stock dividends (44) (44) Capital contributions from parent 180 180 Ending balance, March 31, 2022 $66 $1,884 $1,101 $3,051 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $66 $1,459 $953 $2,478 Net income 84 84 Common stock dividends (42) (42) Capital contributions from parent 125 125 Ending balance, March 31, 2021 $66 $1,584 $995 $2,645
IPL [Member]
Schedule of Capitalization, Equity [Line Items]
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Loss Trust of IPL Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 192 192 Common stock dividends ($0.4275 per share) (107) (107) Shareowner Direct Plan issuances 7 7 Equity-based compensation plans and other (6) 1 (5) Ending balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $2 $2,704 $2,994 ($1) ($11) $200 $5,888 Net income attributable to Alliant Energy common shareowners 171 171 Common stock dividends ($0.4025 per share) (102) (102) Shareowner Direct Plan issuances 1 7 8 Equity-based compensation plans and other 1 1 Ending balance, March 31, 2021 $3 $2,712 $3,063 ($1) ($11) $200 $5,966 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $— $3,769 Net income available for common stock 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $— $3,775 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $33 $2,752 $979 $200 $3,964 Net income available for common stock 79 79 Common stock dividends (101) (101) Ending balance, March 31, 2021 $33 $2,752 $957 $200 $3,942 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $2,823 Net income 92 92 Common stock dividends (44) (44) Capital contributions from parent 180 180 Ending balance, March 31, 2022 $66 $1,884 $1,101 $3,051 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $66 $1,459 $953 $2,478 Net income 84 84 Common stock dividends (42) (42) Capital contributions from parent 125 125 Ending balance, March 31, 2021 $66 $1,584 $995 $2,645
WPL [Member]
Schedule of Capitalization, Equity [Line Items]
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Cumulative Additional Other Deferred Preferred Common Paid-In Retained Comprehensive Compensation Stock Total Stock Capital Earnings Loss Trust of IPL Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 192 192 Common stock dividends ($0.4275 per share) (107) (107) Shareowner Direct Plan issuances 7 7 Equity-based compensation plans and other (6) 1 (5) Ending balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $2 $2,704 $2,994 ($1) ($11) $200 $5,888 Net income attributable to Alliant Energy common shareowners 171 171 Common stock dividends ($0.4025 per share) (102) (102) Shareowner Direct Plan issuances 1 7 8 Equity-based compensation plans and other 1 1 Ending balance, March 31, 2021 $3 $2,712 $3,063 ($1) ($11) $200 $5,966 IPL Total IPL Common Equity Additional Cumulative Common Paid-In Retained Preferred Total Stock Capital Earnings Stock Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $— $3,769 Net income available for common stock 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $— $3,775 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $33 $2,752 $979 $200 $3,964 Net income available for common stock 79 79 Common stock dividends (101) (101) Ending balance, March 31, 2021 $33 $2,752 $957 $200 $3,942 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $2,823 Net income 92 92 Common stock dividends (44) (44) Capital contributions from parent 180 180 Ending balance, March 31, 2022 $66 $1,884 $1,101 $3,051 Three Months Ended March 31, 2021 Beginning balance, December 31, 2020 $66 $1,459 $953 $2,478 Net income 84 84 Common stock dividends (42) (42) Capital contributions from parent 125 125 Ending balance, March 31, 2021 $66 $1,584 $995 $2,645

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2022
Short-term Debt [Line Items]
Other Short-Term Borrowings	Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions): March 31, 2022 Alliant Energy IPL WPL Amount outstanding $276 $— $157 Weighted average interest rates 0.6% N/A 0.5% Available credit facility capacity $724 $250 $143 Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $577 $578 $— $— $252 $275 Average amount outstanding (based on daily outstanding balances) $443 $424 $— $— $205 $189 Weighted average interest rates 0.3% 0.2% —% —% 0.3% 0.2%
IPL [Member]
Short-term Debt [Line Items]
Other Short-Term Borrowings	Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions): March 31, 2022 Alliant Energy IPL WPL Amount outstanding $276 $— $157 Weighted average interest rates 0.6% N/A 0.5% Available credit facility capacity $724 $250 $143 Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $577 $578 $— $— $252 $275 Average amount outstanding (based on daily outstanding balances) $443 $424 $— $— $205 $189 Weighted average interest rates 0.3% 0.2% —% —% 0.3% 0.2%
WPL [Member]
Short-term Debt [Line Items]
Other Short-Term Borrowings	Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions): March 31, 2022 Alliant Energy IPL WPL Amount outstanding $276 $— $157 Weighted average interest rates 0.6% N/A 0.5% Available credit facility capacity $724 $250 $143 Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $577 $578 $— $— $252 $275 Average amount outstanding (based on daily outstanding balances) $443 $424 $— $— $205 $189 Weighted average interest rates 0.3% 0.2% —% —% 0.3% 0.2%

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Electric Utility: Retail - residential $293 $262 $150 $139 $143 $123 Retail - commercial 188 172 118 110 70 62 Retail - industrial 211 202 111 112 100 90 Wholesale 47 40 15 11 32 29 Bulk power and other 34 25 6 14 28 11 Total Electric Utility 773 701 400 386 373 315 Gas Utility: Retail - residential 158 99 85 52 73 47 Retail - commercial 82 53 40 27 42 26 Retail - industrial 8 5 5 3 3 2 Transportation/other 14 13 9 9 5 4 Total Gas Utility 262 170 139 91 123 79 Other Utility: Steam 9 9 9 9 — — Other utility 2 4 2 3 — 1 Total Other Utility 11 13 11 12 — 1 Non-Utility and Other: Travero and other 22 17 — — — — Total Non-Utility and Other 22 17 — — — — Total revenues $1,068 $901 $550 $489 $496 $395
IPL [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Electric Utility: Retail - residential $293 $262 $150 $139 $143 $123 Retail - commercial 188 172 118 110 70 62 Retail - industrial 211 202 111 112 100 90 Wholesale 47 40 15 11 32 29 Bulk power and other 34 25 6 14 28 11 Total Electric Utility 773 701 400 386 373 315 Gas Utility: Retail - residential 158 99 85 52 73 47 Retail - commercial 82 53 40 27 42 26 Retail - industrial 8 5 5 3 3 2 Transportation/other 14 13 9 9 5 4 Total Gas Utility 262 170 139 91 123 79 Other Utility: Steam 9 9 9 9 — — Other utility 2 4 2 3 — 1 Total Other Utility 11 13 11 12 — 1 Non-Utility and Other: Travero and other 22 17 — — — — Total Non-Utility and Other 22 17 — — — — Total revenues $1,068 $901 $550 $489 $496 $395
WPL [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL Three Months Ended March 31 2022 2021 2022 2021 2022 2021 Electric Utility: Retail - residential $293 $262 $150 $139 $143 $123 Retail - commercial 188 172 118 110 70 62 Retail - industrial 211 202 111 112 100 90 Wholesale 47 40 15 11 32 29 Bulk power and other 34 25 6 14 28 11 Total Electric Utility 773 701 400 386 373 315 Gas Utility: Retail - residential 158 99 85 52 73 47 Retail - commercial 82 53 40 27 42 26 Retail - industrial 8 5 5 3 3 2 Transportation/other 14 13 9 9 5 4 Total Gas Utility 262 170 139 91 123 79 Other Utility: Steam 9 9 9 9 — — Other utility 2 4 2 3 — 1 Total Other Utility 11 13 11 12 — 1 Non-Utility and Other: Travero and other 22 17 — — — — Total Non-Utility and Other 22 17 — — — — Total revenues $1,068 $901 $550 $489 $496 $395

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2022
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL. Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Overall income tax rate 4% (19%) (14%) (17%) 19% (29%)
Summary Of Tax Credit Carryforwards	At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $94 $87 $1 State net operating losses 2022-2042 578 13 2 Federal tax credits 2022-2042 589 369 197
IPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL. Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Overall income tax rate 4% (19%) (14%) (17%) 19% (29%)
Summary Of Tax Credit Carryforwards	At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $94 $87 $1 State net operating losses 2022-2042 578 13 2 Federal tax credits 2022-2042 589 369 197
WPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. The increases in Alliant Energy’s and WPL’s overall effective income tax rates for the three months ended March 31, 2022 compared to the same period in 2021 were primarily due to decreased amortization of excess deferred taxes primarily at WPL. Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Overall income tax rate 4% (19%) (14%) (17%) 19% (29%)
Summary Of Tax Credit Carryforwards	At March 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $94 $87 $1 State net operating losses 2022-2042 578 13 2 Federal tax credits 2022-2042 589 369 197

Benefit Plans (Tables)

Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Costs	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Service cost $2 $3 $1 $1 Interest cost 9 8 1 1 Expected return on plan assets (17) (17) (1) (1) Amortization of actuarial loss 8 10 1 1 $2 $4 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Service cost $2 $2 $— $— Interest cost 4 4 1 1 Expected return on plan assets (8) (8) (1) (1) Amortization of actuarial loss 3 4 — — $1 $2 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Service cost $1 $1 $— $— Interest cost 4 4 1 — Expected return on plan assets (8) (8) — — Amortization of actuarial loss 4 5 — 1 $1 $2 $1 $1
Recognized Compensation Expense And Income Tax Benefits	A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Compensation expense $4 $3 $2 $1 $2 $1 Income tax benefits 1 1 1 — — —
Schedule Of Equity-based Compensation Plans Activity	For the three months ended March 31, 2022, performance shares, performance restricted stock units and restricted stock units were granted to key employees as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards. Weighted Average Grants Grant Date Fair Value Performance shares 70,240 $54.45 Performance restricted stock units 80,252 56.62 Restricted stock units 74,360 56.62
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Costs	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Service cost $2 $3 $1 $1 Interest cost 9 8 1 1 Expected return on plan assets (17) (17) (1) (1) Amortization of actuarial loss 8 10 1 1 $2 $4 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Service cost $2 $2 $— $— Interest cost 4 4 1 1 Expected return on plan assets (8) (8) (1) (1) Amortization of actuarial loss 3 4 — — $1 $2 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Service cost $1 $1 $— $— Interest cost 4 4 1 — Expected return on plan assets (8) (8) — — Amortization of actuarial loss 4 5 — 1 $1 $2 $1 $1
Recognized Compensation Expense And Income Tax Benefits	A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Compensation expense $4 $3 $2 $1 $2 $1 Income tax benefits 1 1 1 — — —
Schedule Of Equity-based Compensation Plans Activity	For the three months ended March 31, 2022, performance shares, performance restricted stock units and restricted stock units were granted to key employees as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards. Weighted Average Grants Grant Date Fair Value Performance shares 70,240 $54.45 Performance restricted stock units 80,252 56.62 Restricted stock units 74,360 56.62
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Costs	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans. Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Service cost $2 $3 $1 $1 Interest cost 9 8 1 1 Expected return on plan assets (17) (17) (1) (1) Amortization of actuarial loss 8 10 1 1 $2 $4 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Service cost $2 $2 $— $— Interest cost 4 4 1 1 Expected return on plan assets (8) (8) (1) (1) Amortization of actuarial loss 3 4 — — $1 $2 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Service cost $1 $1 $— $— Interest cost 4 4 1 — Expected return on plan assets (8) (8) — — Amortization of actuarial loss 4 5 — 1 $1 $2 $1 $1
Recognized Compensation Expense And Income Tax Benefits	A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Compensation expense $4 $3 $2 $1 $2 $1 Income tax benefits 1 1 1 — — —
Schedule Of Equity-based Compensation Plans Activity	For the three months ended March 31, 2022, performance shares, performance restricted stock units and restricted stock units were granted to key employees as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards. Weighted Average Grants Grant Date Fair Value Performance shares 70,240 $54.45 Performance restricted stock units 80,252 56.62 Restricted stock units 74,360 56.62

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2022
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of March 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 3,304 2022 175,658 2022-2030 2,653 2022-2023 2,268 2022 IPL 784 2022 94,175 2022-2030 1,053 2022-2023 — — WPL 2,520 2022 81,483 2022-2030 1,600 2022-2023 2,268 2022
Fair Value Of Financial Instruments	Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Current derivative assets $151 $113 $68 $48 $83 $65 Non-current derivative assets 110 63 59 36 51 27 Current derivative liabilities 6 8 3 4 3 4 Non-current derivative liabilities 1 1 1 — — 1
IPL [Member]
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of March 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 3,304 2022 175,658 2022-2030 2,653 2022-2023 2,268 2022 IPL 784 2022 94,175 2022-2030 1,053 2022-2023 — — WPL 2,520 2022 81,483 2022-2030 1,600 2022-2023 2,268 2022
Fair Value Of Financial Instruments	Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Current derivative assets $151 $113 $68 $48 $83 $65 Non-current derivative assets 110 63 59 36 51 27 Current derivative liabilities 6 8 3 4 3 4 Non-current derivative liabilities 1 1 1 — — 1
WPL [Member]
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of March 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 3,304 2022 175,658 2022-2030 2,653 2022-2023 2,268 2022 IPL 784 2022 94,175 2022-2030 1,053 2022-2023 — — WPL 2,520 2022 81,483 2022-2030 1,600 2022-2023 2,268 2022
Fair Value Of Financial Instruments	Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions): Alliant Energy IPL WPL March 31, December 31, March 31, December 31, March 31, December 31, Current derivative assets $151 $113 $68 $48 $83 $65 Non-current derivative assets 110 63 59 36 51 27 Current derivative liabilities 6 8 3 4 3 4 Non-current derivative liabilities 1 1 1 — — 1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Statement [Line Items]
Fair Value Measurements	Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 261 — 251 10 261 176 — 146 30 176 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 7 — 7 — 7 9 — 8 1 9 Long-term debt (incl. current maturities) 7,716 — 7,971 1 7,972 7,368 — 8,329 1 8,330 IPL March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 127 — 120 7 127 84 — 65 19 84 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 4 — 4 — 4 4 — 3 1 4 Long-term debt 3,644 — 3,738 — 3,738 3,643 — 4,124 — 4,124 WPL March 31, 2022 December 31, 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $134 $— $131 $3 $134 $92 $— $81 $11 $92 Liabilities: Derivatives 3 — 3 — 3 5 — 5 — 5 Long-term debt (incl. current maturities) 2,430 — 2,592 — 2,592 2,429 — 2,862 — 2,862
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 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (6) (6) — — Settlements (a) (13) (7) 13 (81) Ending balance, March 31 $10 $16 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($5) ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (4) (5) — — Settlements (a) (7) (6) 13 (81) Ending balance, March 31 $7 $15 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($4) ($6) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2022 2021 Beginning balance, January 1 $11 $3 Total net losses included in changes in net assets (realized/unrealized) (2) (1) Settlements (6) (1) Ending balance, March 31 $3 $1 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($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	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2022 $3 $7 $3 $4 $— $3 December 31, 2021 9 20 8 10 1 10
IPL [Member]
Statement [Line Items]
Fair Value Measurements	Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 261 — 251 10 261 176 — 146 30 176 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 7 — 7 — 7 9 — 8 1 9 Long-term debt (incl. current maturities) 7,716 — 7,971 1 7,972 7,368 — 8,329 1 8,330 IPL March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 127 — 120 7 127 84 — 65 19 84 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 4 — 4 — 4 4 — 3 1 4 Long-term debt 3,644 — 3,738 — 3,738 3,643 — 4,124 — 4,124 WPL March 31, 2022 December 31, 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $134 $— $131 $3 $134 $92 $— $81 $11 $92 Liabilities: Derivatives 3 — 3 — 3 5 — 5 — 5 Long-term debt (incl. current maturities) 2,430 — 2,592 — 2,592 2,429 — 2,862 — 2,862
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 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (6) (6) — — Settlements (a) (13) (7) 13 (81) Ending balance, March 31 $10 $16 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($5) ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (4) (5) — — Settlements (a) (7) (6) 13 (81) Ending balance, March 31 $7 $15 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($4) ($6) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2022 2021 Beginning balance, January 1 $11 $3 Total net losses included in changes in net assets (realized/unrealized) (2) (1) Settlements (6) (1) Ending balance, March 31 $3 $1 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($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	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2022 $3 $7 $3 $4 $— $3 December 31, 2021 9 20 8 10 1 10
WPL [Member]
Statement [Line Items]
Fair Value Measurements	Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions): Alliant Energy March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 261 — 251 10 261 176 — 146 30 176 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 7 — 7 — 7 9 — 8 1 9 Long-term debt (incl. current maturities) 7,716 — 7,971 1 7,972 7,368 — 8,329 1 8,330 IPL March 31, 2022 December 31, 2021 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 $59 $59 $— $— $59 $32 $32 $— $— $32 Derivatives 127 — 120 7 127 84 — 65 19 84 Deferred proceeds 227 — — 227 227 214 — — 214 214 Liabilities: Derivatives 4 — 4 — 4 4 — 3 1 4 Long-term debt 3,644 — 3,738 — 3,738 3,643 — 4,124 — 4,124 WPL March 31, 2022 December 31, 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $134 $— $131 $3 $134 $92 $— $81 $11 $92 Liabilities: Derivatives 3 — 3 — 3 5 — 5 — 5 Long-term debt (incl. current maturities) 2,430 — 2,592 — 2,592 2,429 — 2,862 — 2,862
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 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (6) (6) — — Settlements (a) (13) (7) 13 (81) Ending balance, March 31 $10 $16 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($5) ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (4) (5) — — Settlements (a) (7) (6) 13 (81) Ending balance, March 31 $7 $15 $227 $107 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($4) ($6) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2022 2021 Beginning balance, January 1 $11 $3 Total net losses included in changes in net assets (realized/unrealized) (2) (1) Settlements (6) (1) Ending balance, March 31 $3 $1 The amount of total net losses for the period included in changes in net liabilities attributable to the change in unrealized losses relating to liabilities held at March 31 ($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	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2022 $3 $7 $3 $4 $— $3 December 31, 2021 9 20 8 10 1 10

Commitments And Contingencies (

Commitments And Contingencies (Tables)	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At March 31, 2022, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $939 $472 $467 Coal 127 72 55 Other (a) 135 66 36 $1,201 $610 $558 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2022.
MGP Site Estimated Future Costs And Recorded Liabilities	At March 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At March 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $10 - $26 $7 - $20 Current and non-current environmental liabilities $12 $9
IPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At March 31, 2022, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $939 $472 $467 Coal 127 72 55 Other (a) 135 66 36 $1,201 $610 $558 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2022.
MGP Site Estimated Future Costs And Recorded Liabilities	At March 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At March 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $10 - $26 $7 - $20 Current and non-current environmental liabilities $12 $9
WPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At March 31, 2022, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $939 $472 $467 Coal 127 72 55 Other (a) 135 66 36 $1,201 $610 $558 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2022.

Segments Of Business (Tables)

Segments Of Business (Tables)	3 Months Ended
	Mar. 31, 2022
Segment Reporting Information [Line Items]
Schedule Of Segments Of Business	Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations. Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2022 Revenues $773 $262 $11 $1,046 $22 $1,068 Operating income 181 57 3 241 7 248 Net income attributable to Alliant Energy common shareowners 179 13 192 Three Months Ended March 31, 2021 Revenues $701 $170 $13 $884 $17 $901 Operating income 147 44 2 193 5 198 Net income attributable to Alliant Energy common shareowners 163 8 171 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income available for common stock 87 Three Months Ended March 31, 2021 Revenues $386 $91 $12 $489 Operating income 72 30 1 103 Net income available for common stock 79 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92 Three Months Ended March 31, 2021 Revenues $315 $79 $1 $395 Operating income 75 14 1 90 Net income 84
IPL [Member]
Segment Reporting Information [Line Items]
Schedule Of Segments Of Business	Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations. Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2022 Revenues $773 $262 $11 $1,046 $22 $1,068 Operating income 181 57 3 241 7 248 Net income attributable to Alliant Energy common shareowners 179 13 192 Three Months Ended March 31, 2021 Revenues $701 $170 $13 $884 $17 $901 Operating income 147 44 2 193 5 198 Net income attributable to Alliant Energy common shareowners 163 8 171 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income available for common stock 87 Three Months Ended March 31, 2021 Revenues $386 $91 $12 $489 Operating income 72 30 1 103 Net income available for common stock 79 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92 Three Months Ended March 31, 2021 Revenues $315 $79 $1 $395 Operating income 75 14 1 90 Net income 84
WPL [Member]
Segment Reporting Information [Line Items]
Schedule Of Segments Of Business	Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations. Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2022 Revenues $773 $262 $11 $1,046 $22 $1,068 Operating income 181 57 3 241 7 248 Net income attributable to Alliant Energy common shareowners 179 13 192 Three Months Ended March 31, 2021 Revenues $701 $170 $13 $884 $17 $901 Operating income 147 44 2 193 5 198 Net income attributable to Alliant Energy common shareowners 163 8 171 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income available for common stock 87 Three Months Ended March 31, 2021 Revenues $386 $91 $12 $489 Operating income 72 30 1 103 Net income available for common stock 79 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92 Three Months Ended March 31, 2021 Revenues $315 $79 $1 $395 Operating income 75 14 1 90 Net income 84

Related Parties (Tables)

Related Parties (Tables)	3 Months Ended
	Mar. 31, 2022
Related Party Transactions [Line Items]
Services Provided, Sales Credited And Purchases	The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions): IPL WPL 2022 2021 2022 2021 Corporate Services billings $40 $40 $36 $35 Sales credited — 1 18 1 Purchases billed 94 143 22 26
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2022 December 31, 2021 March 31, 2022 December 31, 2021 Net payables to Corporate Services $120 $110 $76 $83
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three months ended March 31 were as follows (in millions): 2022 2021 ATC billings to WPL $34 $32 WPL billings to ATC 3 3
IPL [Member]
Related Party Transactions [Line Items]
Services Provided, Sales Credited And Purchases	The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions): IPL WPL 2022 2021 2022 2021 Corporate Services billings $40 $40 $36 $35 Sales credited — 1 18 1 Purchases billed 94 143 22 26
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2022 December 31, 2021 March 31, 2022 December 31, 2021 Net payables to Corporate Services $120 $110 $76 $83
WPL [Member]
Related Party Transactions [Line Items]
Services Provided, Sales Credited And Purchases	The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions): IPL WPL 2022 2021 2022 2021 Corporate Services billings $40 $40 $36 $35 Sales credited — 1 18 1 Purchases billed 94 143 22 26
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2022 December 31, 2021 March 31, 2022 December 31, 2021 Net payables to Corporate Services $120 $110 $76 $83
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three months ended March 31 were as follows (in millions): 2022 2021 ATC billings to WPL $34 $32 WPL billings to ATC 3 3

Summary Of Significant Accoun_3

Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 59	$ 32
Money market fund investments interest rate, percentage	0.30%
IPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 59	$ 32
Money market fund investments interest rate, percentage	0.30%

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Regulatory Assets [Line Items]
Regulatory assets	$ 1,919	$ 1,940
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	949	934
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	453	462
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	134	128
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	88	92
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	84	90
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	50	52
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	42
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	119	140
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,432	1,443
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	896	884
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	224	228
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	94	89
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	64	66
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	84	90
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	2	2
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	68	84
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	487	497
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	53	50
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	229	234
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	40	39
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	24	26
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	50	52
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	40	40
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 51	$ 56

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,372	$ 1,271
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	578	585
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	391	384
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	258	166
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	50	51
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	35	36
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	60	49
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	754	691
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	310	312
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	256	252
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	125	77
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	29	27
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	34	23
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	618	580
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	268	273
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	135	132
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	133	89
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	21	24
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	35	36
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 26	$ 26

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) - Receivables Sold [Member] - IPL [Member] $ in Millions	Mar. 31, 2022USD ($)
Receivables [Line Items]
Available capacity	$ 109
Financial Asset, Past Due [Member]
Receivables [Line Items]
Outstanding receivables past due	$ 24

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Maximum [Member]
Receivables [Line Items]
Maximum outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 36	$ 100
Average [Member]
Receivables [Line Items]
Average outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 4	$ 30

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Receivables [Line Items]
Fair value of deferred proceeds	$ 227	$ 214
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	227	214
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	142	125
Unbilled utility revenues	96	104
Receivables sold to third party	238	229
Less: cash proceeds	1	1
Deferred proceeds	237	228
Less: allowance for expected credit losses	10	14
Fair value of deferred proceeds	$ 227	$ 214

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Receivables [Line Items]
Collections	$ 561	$ 529
Write-offs, net of recoveries	$ 2	$ 2

Investments (Unconsolidated Equ

Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	$ (15)	$ (15)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	(11)	(11)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	(4)	(4)
Totals [Member]
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	$ (15)	$ (15)

Common Equity (Common Share Act

Common Equity (Common Share Activity) (Details)	3 Months Ended
	Mar. 31, 2022shares
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1, 2022 (in shares)	250,474,529
Shareowner Direct Plan (in shares)	116,431
Equity-based compensation plans (in shares)	222,768
Shares outstanding, March 31, 2022 (in shares)	250,813,728

Common Equity (Changes in Share

Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 5,990
Beginning balance	5,990	$ 5,888
Net income attributable to common shareowners	192	171
Net income	192	174
Common stock dividends	(107)	(102)
Shareowner Direct Plan issuances	7	8
Equity-based compensation plans and other	(5)	1
Ending balance	6,077
Ending balance	$ 6,077	$ 5,966
Common stock dividends (in dollars per share)	$ 0.4275	$ 0.4025
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 3	$ 2
Shareowner Direct Plan issuances		1
Ending balance	3	3
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,749	2,704
Shareowner Direct Plan issuances	7	7
Equity-based compensation plans and other	(6)	1
Ending balance	2,750	2,712
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,250	2,994
Net income attributable to common shareowners	192	171
Common stock dividends	(107)	(102)
Equity-based compensation plans and other	1
Ending balance	3,336	3,063
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	(1)
Ending balance	0	(1)
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(12)	(11)
Ending balance	(12)	(11)
Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	200
Ending balance	0	200
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,769
Beginning balance	3,769	3,964
Net income attributable to common shareowners	87	79
Net income	87	82
Common stock dividends	(81)	(101)
Ending balance	3,775
Ending balance	3,775	3,942
IPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	33	33
Ending balance	33	33
IPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,807	2,752
Ending balance	2,807	2,752
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	929	979
Net income attributable to common shareowners	87	79
Common stock dividends	(81)	(101)
Ending balance	935	957
IPL [Member] | Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	200
Ending balance	0	200
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,823
Beginning balance	2,823	2,478
Net income	92	84
Common stock dividends	(44)	(42)
Capital contributions from parent	180	125
Ending balance	3,051
Ending balance	3,051	2,645
WPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	66	66
Ending balance	66	66
WPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,704	1,459
Capital contributions from parent	180	125
Ending balance	1,884	1,584
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,053	953
Net income	92	84
Common stock dividends	(44)	(42)
Ending balance	$ 1,101	$ 995

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Senior Notes [Member] | 3.6% senior notes, due 2032 [Member]
Debt [Line Items]
Long-term debt	$ 350
Interest rate, percent	3.60%
Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024
Debt [Line Items]
Long-term debt	$ 300
Interest rate, percent	1.00%
Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2022
Debt [Line Items]
Long-term debt		$ 300

Debt (Credit Facilities) (Detai

Debt (Credit Facilities) (Details) $ in Millions	Mar. 31, 2022USD ($)
Debt [Line Items]
Amount outstanding	$ 276
Weighted average interest rates	0.60%
Available credit facility capacity	$ 724
IPL [Member]
Debt [Line Items]
Amount outstanding	0
Available credit facility capacity	250
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 157
Weighted average interest rates	0.50%
Available credit facility capacity	$ 143

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 577	$ 578
Average amount outstanding (based on daily outstanding balances)	$ 443	$ 424
Weighted average interest rates	0.30%	0.20%
IPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 0	$ 0
Average amount outstanding (based on daily outstanding balances)	$ 0	$ 0
Weighted average interest rates	0.00%	0.00%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 252	$ 275
Average amount outstanding (based on daily outstanding balances)	$ 205	$ 189
Weighted average interest rates	0.30%	0.20%

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,068	$ 901
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	773	701
Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	293	262
Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	188	172
Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	211	202
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47	40
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	25
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	262	170
Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	158	99
Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	82	53
Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8	5
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	13
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	13
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	9
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	4
Non-utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	17
Non-utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	17
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	550	489
IPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	400	386
IPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	150	139
IPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	118	110
IPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	111	112
IPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	15	11
IPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	14
IPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	139	91
IPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85	52
IPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	40	27
IPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	3
IPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	9
IPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	12
IPL [Member] | Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	9
IPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	3
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	496	395
WPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	373	315
WPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	143	123
WPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	70	62
WPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	100	90
WPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32	29
WPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	28	11
WPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	123	79
WPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	73	47
WPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	42	26
WPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	2
WPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	4
WPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1
WPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 1

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2023
Income Taxes [Line Items]
State income tax rate, percent	9.80%
Forecast [Member]
Income Taxes [Line Items]
State income tax rate, percent		5.50%

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Effective Tax Rate [Line Items]
Overall income tax rate	4.00%	(19.00%)
IPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	(14.00%)	(17.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	19.00%	(29.00%)

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Mar. 31, 2022USD ($)
Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 94
Tax credits, carryforward amount	589
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	578
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	87
Tax credits, carryforward amount	369
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	13
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
Tax credits, carryforward amount	197
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 2

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)shares
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 15
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	1 year
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	2 years
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 8
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 6
Omnibus Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Shares included in diluted earnings per share (in shares) | shares	322,288

Benefit Plans (Defined Benefit

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 3
Interest cost	9	8
Expected return on plan assets	(17)	(17)
Amortization of actuarial loss	8	10
Total	2	4
OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	1	1
Expected return on plan assets	(1)	(1)
Amortization of actuarial loss	1	1
Total	2	2
IPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2
Interest cost	4	4
Expected return on plan assets	(8)	(8)
Amortization of actuarial loss	3	4
Total	1	2
IPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	(1)	(1)
Amortization of actuarial loss	0	0
Total	0	0
WPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	4	4
Expected return on plan assets	(8)	(8)
Amortization of actuarial loss	4	5
Total	1	2
WPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	0
Expected return on plan assets	0	0
Amortization of actuarial loss	0	1
Total	$ 1	$ 1

Benefit Plans (Recognized Compe

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Compensation expense	$ 4	$ 3
Income tax benefits	1	1
IPL [Member]
Compensation expense	2	1
Income tax benefits	1	0
WPL [Member]
Compensation expense	2	1
Income tax benefits	$ 0	$ 0

Benefit Plans (Summary Of Equit

Benefit Plans (Summary Of Equity-based Compensation Plans Grants) (Details)	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	70,240
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 54.45
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	80,252
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 56.62
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	74,360
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 56.62

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] gal in Thousands, T in Thousands, MWh in Thousands, Dekatherms in Thousands	3 Months Ended
	Mar. 31, 2022DekathermsMWhTgal
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	3,304
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	784
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	2,520
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	175,658
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	94,175
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	81,483
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	2,653
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	1,053
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	1,600
Diesel Fuel (Gallons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	2,268
Diesel Fuel (Gallons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	0
Diesel Fuel (Gallons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	2,268

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 151	$ 113
Non-current derivative assets	110	63
Current derivative liabilities	6	8
Non-current derivative liabilities	1	1
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	68	48
Non-current derivative assets	59	36
Current derivative liabilities	3	4
Non-current derivative liabilities	1	0
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	83	65
Non-current derivative assets	51	27
Current derivative liabilities	3	4
Non-current derivative liabilities	$ 0	$ 1

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Assets:
Money market fund investments	$ 59	$ 32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	7,972	8,330
IPL [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	3,738	4,124
WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,592	2,862
Commodity Contracts [Member]
Assets:
Derivatives	261	176
Liabilities:
Derivatives	7	9
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	127	84
Liabilities:
Derivatives	4	4
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	134	92
Liabilities:
Derivatives	3	5
Level 1 [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	7,971	8,329
Level 2 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,738	4,124
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,592	2,862
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	251	146
Liabilities:
Derivatives	7	8
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	120	65
Liabilities:
Derivatives	4	3
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	131	81
Liabilities:
Derivatives	3	5
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	1	1
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	10	30
Liabilities:
Derivatives	0	1
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	7	19
Liabilities:
Derivatives	0	1
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	3	11
Liabilities:
Derivatives	0	0
Carrying Amount [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	7,716	7,368
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	3,644	3,643
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,430	2,429
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	261	176
Liabilities:
Derivatives	7	9
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	127	84
Liabilities:
Derivatives	4	4
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	134	92
Liabilities:
Derivatives	$ 3	$ 5

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 29	$ 29
Total net losses included in changes in net assets (realized/unrealized)	(6)	(6)
Settlements	(13)	(7)
Ending balance	10	16
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	(5)	(6)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	18	26
Total net losses included in changes in net assets (realized/unrealized)	(4)	(5)
Settlements	(7)	(6)
Ending balance	7	15
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	(4)	(6)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	11	3
Total net losses included in changes in net assets (realized/unrealized)	(2)	(1)
Settlements	(6)	(1)
Ending balance	3	1
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	(1)	0
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	214	188
Total net losses included in changes in net assets (realized/unrealized)	0	0
Settlements	13	(81)
Ending balance	227	107
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	0	0
Deferred Proceeds [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	214	188
Total net losses included in changes in net assets (realized/unrealized)	0	0
Settlements	13	(81)
Ending balance	227	107
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	$ 0	$ 0

Fair Value Measurements (Fair_3

Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 10	$ 29	$ 16	$ 29
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3	9
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	7	20
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	7	18	15	26
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3	8
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	4	10
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3	11	$ 1	$ 3
WPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	0	1
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 3	$ 10

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,201
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	610
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	558
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	214
Capital Purchase Commitment [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	213
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	67
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	$ 17
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreements	55.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreements	70.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreements	83.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreements	26.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreements	83.00%
Whiting Petroleum Affiliate [Member]
Commitments and Contingencies [Line Items]
Partnership share, percent	6.00%
Obligations, maximum	$ 60
Credit loss liability	$ 5

Commitments And Contingencies_3

Commitments And Contingencies (Other Purchase Commitments) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,201
Individual commitments incurred	1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	610
Individual commitments incurred	1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	558
Individual commitments incurred	1
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	939
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	472
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	467
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	127
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	72
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	55
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	135
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	66
Other [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 36

Commitments And Contingencies_4

Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	$ 12
IPL [Member]
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	9
Minimum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	10
Minimum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	7
Maximum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	26
Maximum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	$ 20

Segments Of Business (Schedule

Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Revenues	$ 1,068	$ 901
Operating income (loss)	248	198
Net income attributable to common shareowners	192	171
Net income	192	174
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	550	489
Operating income (loss)	110	103
Net income attributable to common shareowners	87	79
Net income	87	82
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	496	395
Operating income (loss)	131	90
Net income	92	84
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	773	701
Operating income (loss)	181	147
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	400	386
Operating income (loss)	75	72
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	373	315
Operating income (loss)	106	75
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	262	170
Operating income (loss)	57	44
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	139	91
Operating income (loss)	32	30
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	123	79
Operating income (loss)	25	14
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	11	13
Operating income (loss)	3	2
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	11	12
Operating income (loss)	3	1
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0	1
Operating income (loss)	0	1
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	1,046	884
Operating income (loss)	241	193
Net income attributable to common shareowners	179	163
ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	22	17
Operating income (loss)	7	5
Net income attributable to common shareowners	$ 13	$ 8

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
WPL [Member] | ATC LLC [Member] | WPL Owed ATC LLC [Member] | Equity Method Investee [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 9	$ 10

Related Parties (Service Agreem

Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Corporate Services Billings [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 40	$ 40
Corporate Services Billings [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	36	35
Sales Credited [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	0	1
Sales Credited [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	18	1
Purchases Billed [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	94	143
Purchases Billed [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 22	$ 26

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Subsidiary of Common Parent [Member] - Corporate Services [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 120	$ 110
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 76	$ 83

Related Parties (Amounts Billed

Related Parties (Amounts Billed Between Parties) (Details) - ATC LLC [Member] - Equity Method Investee [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
ATC Billings To WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 34	$ 32
WPL Billings To ATC [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 3	$ 3