Wisconsin Power & Light 10-Q 5 May 23 2023 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	3 Months Ended
	Mar. 31, 2023 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
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	251,387,788
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
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, 2023	Mar. 31, 2022
Revenues:
Electric utility	$ 768	$ 773
Gas utility	276	262
Other utility	11	11
Non-utility	22	22
Total revenues	1,077	1,068
Operating expenses:
Electric production fuel and purchased power	157	168
Electric transmission service	146	138
Cost of gas sold	181	168
Other operation and maintenance	174	153
Depreciation and amortization	166	166
Taxes other than income taxes	31	27
Total operating expenses	855	820
Operating income	222	248
Other (income) and deductions:
Interest expense	94	74
Equity income from unconsolidated investments, net	(17)	(15)
Allowance for funds used during construction	(19)	(11)
Other	3	0
Total other (income) and deductions	61	48
Income before income taxes	161	200
Income tax expense (benefit)	(2)	8
Net income	163	192
Net income attributable to common shareowners	$ 163	$ 192
Weighted average number of common shares outstanding:
Basic (in shares)	251,200	250,600
Diluted (in shares)	251,400	250,900
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 0.65	$ 0.77
Diluted (in dollars per share)	$ 0.65	$ 0.77
IPL [Member]
Revenues:
Electric utility	$ 388	$ 400
Gas utility	150	139
Other utility	11	11
Total revenues	549	550
Operating expenses:
Electric production fuel and purchased power	47	67
Electric transmission service	104	97
Cost of gas sold	95	85
Other operation and maintenance	95	83
Depreciation and amortization	96	94
Taxes other than income taxes	16	14
Total operating expenses	453	440
Operating income	96	110
Other (income) and deductions:
Interest expense	37	37
Allowance for funds used during construction	(3)	(3)
Other	1	0
Total other (income) and deductions	35	34
Income before income taxes	61	76
Income tax expense (benefit)	(11)	(11)
Net income	72	87
WPL [Member]
Revenues:
Electric utility	380	373
Gas utility	126	123
Total revenues	506	496
Operating expenses:
Electric production fuel and purchased power	109	101
Electric transmission service	42	41
Cost of gas sold	86	83
Other operation and maintenance	66	58
Depreciation and amortization	68	70
Taxes other than income taxes	14	12
Total operating expenses	385	365
Operating income	121	131
Other (income) and deductions:
Interest expense	36	27
Allowance for funds used during construction	(16)	(9)
Other	1	0
Total other (income) and deductions	21	18
Income before income taxes	100	113
Income tax expense (benefit)	12	21
Net income	$ 88	$ 92

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 157	$ 20
Accounts receivable, less allowance for expected credit losses	428	516
Production fuel, at weighted average cost	60	53
Gas stored underground, at weighted average cost	64	132
Materials and supplies, at weighted average cost	158	140
Regulatory assets	193	166
Other	132	223
Total current assets	1,192	1,250
Property, plant and equipment, net	16,396	16,247
Investments:
ATC Holdings	363	358
Other	206	201
Total investments	569	559
Other assets:
Regulatory assets	1,887	1,880
Deferred charges and other	196	227
Total other assets	2,083	2,107
Total assets	20,240	20,163
Current liabilities:
Current maturities of long-term debt	808	408
Commercial paper	60	642
Other short-term borrowings	50	0
Accounts payable	518	756
Regulatory liabilities	129	206
Other	343	351
Total current liabilities	1,908	2,363
Long-term debt, net (excluding current portion)	8,132	7,668
Other liabilities:
Deferred tax liabilities	1,957	1,943
Regulatory liabilities	1,102	1,118
Pension and other benefit obligations	273	277
Other	540	518
Total other liabilities	3,872	3,856
Commitments and contingencies (Note 13)
Common equity:
Common stock	3	3
Additional paid-in capital	2,780	2,777
Retained earnings	3,559	3,509
Accumulated other comprehensive loss	(1)	0
Shares in deferred compensation trust - 394,363 and 402,134 shares at a weighted average cost of $33.12 and $32.63 per share	(13)	(13)
Total common equity	6,328	6,276
Total liabilities and equity	20,240	20,163
IPL [Member]
Current assets:
Cash and cash equivalents	35	15
Accounts receivable, less allowance for expected credit losses	191	259
Production fuel, at weighted average cost	26	23
Gas stored underground, at weighted average cost	26	60
Materials and supplies, at weighted average cost	92	83
Regulatory assets	75	85
Other	49	93
Total current assets	494	618
Property, plant and equipment, net	8,112	8,046
Other assets:
Regulatory assets	1,308	1,301
Deferred charges and other	93	110
Total other assets	1,401	1,411
Total assets	10,007	10,075
Current liabilities:
Accounts payable	222	239
Accounts payable to associated companies	37	28
Accrued taxes	59	52
Accrued interest	35	35
Regulatory liabilities	73	114
Other	92	113
Total current liabilities	518	581
Long-term debt, net (excluding current portion)	3,647	3,646
Other liabilities:
Deferred tax liabilities	1,053	1,047
Regulatory liabilities	624	640
Pension and other benefit obligations	61	62
Other	294	291
Total other liabilities	2,032	2,040
Commitments and contingencies (Note 13)
Common equity:
Common stock	33	33
Additional paid-in capital	2,807	2,807
Retained earnings	970	968
Total common equity	3,810	3,808
Total liabilities and equity	10,007	10,075
WPL [Member]
Current assets:
Cash and cash equivalents	86	5
Accounts receivable, less allowance for expected credit losses	225	244
Production fuel, at weighted average cost	34	29
Gas stored underground, at weighted average cost	38	73
Materials and supplies, at weighted average cost	63	54
Regulatory assets	118	81
Prepaid gross receipts tax	31	42
Other	26	60
Total current assets	621	588
Property, plant and equipment, net	7,792	7,722
Other assets:
Regulatory assets	579	579
Deferred charges and other	82	98
Total other assets	661	677
Total assets	9,074	8,987
Current liabilities:
Commercial paper	60	290
Accounts payable	233	456
Regulatory liabilities	56	92
Other	163	111
Total current liabilities	512	949
Long-term debt, net (excluding current portion)	3,067	2,770
Other liabilities:
Deferred tax liabilities	787	789
Regulatory liabilities	478	478
Pension and other benefit obligations	139	140
Other	378	370
Total other liabilities	1,782	1,777
Commitments and contingencies (Note 13)
Common equity:
Common stock	66	66
Additional paid-in capital	2,413	2,233
Retained earnings	1,234	1,192
Total common equity	3,713	3,491
Total liabilities and equity	$ 9,074	$ 8,987

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
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)	251,387,788	251,134,966
Shares in deferred compensation trust (in shares)	394,363	402,134
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 33.12	$ 32.63
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, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net income	$ 163	$ 192
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	166	166
Other	(6)	12
Other changes in assets and liabilities:
Accounts receivable	(86)	(161)
Gas stored underground	68	55
Derivative assets	115	(85)
Regulatory assets	(32)	19
Accounts payable	(97)	(37)
Regulatory liabilities	(95)	92
Other	(8)	(2)
Net cash flows from operating activities	188	251
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(417)	(307)
Other construction and acquisition expenditures	(34)	(23)
Cash receipts on sold receivables	173	115
Proceeds from sale of partial ownership interest in West Riverside	25	0
Other	(10)	(8)
Net cash flows from (used for) investing activities	(263)	(223)
Cash flows from (used for) financing activities:
Common stock dividends	(113)	(107)
Proceeds from issuance of long-term debt	862	650
Payments to retire long-term debt	0	(300)
Net change in commercial paper and other short-term borrowings	(532)	(239)
Other	(5)	(1)
Net cash flows from (used for) financing activities	212	3
Net increase (decrease) in cash, cash equivalents and restricted cash	137	31
Cash, cash equivalents and restricted cash at beginning of period	24	40
Cash, cash equivalents and restricted cash at end of period	161	71
Supplemental cash flows information:
Interest	(93)	(62)
Significant non-cash investing and financing activities:
Accrued capital expenditures	254	134
Beneficial interest obtained in exchange for securitized accounts receivable	153	227
IPL [Member]
Cash flows from operating activities:
Net income	72	87
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	96	94
Deferred tax expense (benefit) and tax credits	3	15
Other	(2)	(2)
Other changes in assets and liabilities:
Accounts receivable	(106)	(128)
Income tax refunds receivable	(7)	(17)
Gas stored underground	34	29
Derivative assets	69	(43)
Accounts payable	(56)	(8)
Regulatory liabilities	(59)	59
Other	(20)	3
Net cash flows from operating activities	24	89
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(101)	(96)
Cash receipts on sold receivables	173	115
Other	(2)	(1)
Net cash flows from (used for) investing activities	70	18
Cash flows from (used for) financing activities:
Common stock dividends	(70)	(81)
Other	(4)	2
Net cash flows from (used for) financing activities	(74)	(79)
Net increase (decrease) in cash, cash equivalents and restricted cash	20	28
Cash, cash equivalents and restricted cash at beginning of period	15	34
Cash, cash equivalents and restricted cash at end of period	35	62
Supplemental cash flows information:
Interest	(37)	(37)
Significant non-cash investing and financing activities:
Accrued capital expenditures	98	27
Beneficial interest obtained in exchange for securitized accounts receivable	153	227
WPL [Member]
Cash flows from operating activities:
Net income	88	92
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	68	70
Other	(12)	(5)
Other changes in assets and liabilities:
Accounts receivable	19	(23)
Gas stored underground	35	26
Derivative assets	46	(42)
Regulatory assets	(37)	10
Accounts payable	(48)	(24)
Derivative liabilities	28	(2)
Regulatory liabilities	(35)	32
Accrued taxes	19	21
Other	14	12
Net cash flows from operating activities	185	167
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(316)	(212)
Proceeds from sale of partial ownership interest in West Riverside	25	0
Other	(4)	(5)
Net cash flows from (used for) investing activities	(295)	(217)
Cash flows from (used for) financing activities:
Common stock dividends	(46)	(44)
Capital contributions from parent	180	180
Proceeds from issuance of long-term debt	297	0
Net change in commercial paper and other short-term borrowings	(230)	(79)
Other	(10)	(5)
Net cash flows from (used for) financing activities	191	52
Net increase (decrease) in cash, cash equivalents and restricted cash	81	2
Cash, cash equivalents and restricted cash at beginning of period	5	2
Cash, cash equivalents and restricted cash at end of period	86	4
Supplemental cash flows information:
Interest	(40)	(23)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 152	$ 104

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2023
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 2022 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, 2023 are not necessarily indicative of results that may be expected for the year ending December 31, 2023. 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 and Cash Equivalents - At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $148 million, $30 million and $83 million of money market fund investments, respectively, with interest rates of 5%.
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 2022 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, 2023 are not necessarily indicative of results that may be expected for the year ending December 31, 2023. 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 and Cash Equivalents - At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $148 million, $30 million and $83 million of money market fund investments, respectively, with interest rates of 5%.
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 2022 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, 2023 are not necessarily indicative of results that may be expected for the year ending December 31, 2023. 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 and Cash Equivalents - At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $148 million, $30 million and $83 million of money market fund investments, respectively, with interest rates of 5%.

Regulatory Matters

Regulatory Matters	3 Months Ended
	Mar. 31, 2023
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 $942 $929 $857 $848 $85 $81 Pension and OPEB costs 385 392 193 197 192 195 Asset retirement obligations 156 151 115 110 41 41 Commodity cost recovery 152 160 4 1 148 159 Derivatives 101 84 37 48 64 36 Assets retired early 67 70 51 53 16 17 IPL’s Duane Arnold Energy Center PPA amendment 60 66 60 66 — — WPL’s Western Wisconsin gas distribution expansion investments 48 48 — — 48 48 Other 169 146 66 63 103 83 $2,080 $2,046 $1,383 $1,386 $697 $660 Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 2023, which result in comparable changes to regulatory assets/liabilities on the balance sheets. 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 $575 $579 $302 $303 $273 $276 Cost of removal obligations 403 398 261 259 142 139 Derivatives 117 210 64 115 53 95 Electric transmission cost recovery 26 20 19 10 7 10 WPL’s West Riverside liquidated damages 24 32 — — 24 32 Commodity cost recovery 22 40 8 38 14 2 Other 64 45 43 29 21 16 $1,231 $1,324 $697 $754 $534 $570
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 $942 $929 $857 $848 $85 $81 Pension and OPEB costs 385 392 193 197 192 195 Asset retirement obligations 156 151 115 110 41 41 Commodity cost recovery 152 160 4 1 148 159 Derivatives 101 84 37 48 64 36 Assets retired early 67 70 51 53 16 17 IPL’s Duane Arnold Energy Center PPA amendment 60 66 60 66 — — WPL’s Western Wisconsin gas distribution expansion investments 48 48 — — 48 48 Other 169 146 66 63 103 83 $2,080 $2,046 $1,383 $1,386 $697 $660 Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 2023, which result in comparable changes to regulatory assets/liabilities on the balance sheets. 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 $575 $579 $302 $303 $273 $276 Cost of removal obligations 403 398 261 259 142 139 Derivatives 117 210 64 115 53 95 Electric transmission cost recovery 26 20 19 10 7 10 WPL’s West Riverside liquidated damages 24 32 — — 24 32 Commodity cost recovery 22 40 8 38 14 2 Other 64 45 43 29 21 16 $1,231 $1,324 $697 $754 $534 $570
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 $942 $929 $857 $848 $85 $81 Pension and OPEB costs 385 392 193 197 192 195 Asset retirement obligations 156 151 115 110 41 41 Commodity cost recovery 152 160 4 1 148 159 Derivatives 101 84 37 48 64 36 Assets retired early 67 70 51 53 16 17 IPL’s Duane Arnold Energy Center PPA amendment 60 66 60 66 — — WPL’s Western Wisconsin gas distribution expansion investments 48 48 — — 48 48 Other 169 146 66 63 103 83 $2,080 $2,046 $1,383 $1,386 $697 $660 Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 2023, which result in comparable changes to regulatory assets/liabilities on the balance sheets. 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 $575 $579 $302 $303 $273 $276 Cost of removal obligations 403 398 261 259 142 139 Derivatives 117 210 64 115 53 95 Electric transmission cost recovery 26 20 19 10 7 10 WPL’s West Riverside liquidated damages 24 32 — — 24 32 Commodity cost recovery 22 40 8 38 14 2 Other 64 45 43 29 21 16 $1,231 $1,324 $697 $754 $534 $570

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2023
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENTIn March 2023, Madison Gas and Electric Company acquired a partial ownership interest in West Riverside, and the related proceeds are included in “Proceeds from sale of partial ownership interest in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flow statements for the three months ended March 31, 2023. As a result of this transaction, WPL’s undivided current ownership interest in West Riverside is 87.6%.
IPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENTIn March 2023, Madison Gas and Electric Company acquired a partial ownership interest in West Riverside, and the related proceeds are included in “Proceeds from sale of partial ownership interest in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flow statements for the three months ended March 31, 2023. As a result of this transaction, WPL’s undivided current ownership interest in West Riverside is 87.6%.
WPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENTIn March 2023, Madison Gas and Electric Company acquired a partial ownership interest in West Riverside, and the related proceeds are included in “Proceeds from sale of partial ownership interest in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flow statements for the three months ended March 31, 2023. As a result of this transaction, WPL’s undivided current ownership interest in West Riverside is 87.6%.

Receivables

Receivables	3 Months Ended
	Mar. 31, 2023
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three months ended March 31, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable, which originated in 2022, were $5 million, $3 million and $2 million, respectively. NOTE 4(b) - 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. In March 2023, IPL amended and extended through March 2024 the purchase commitment from the third party to which it sells its receivables. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of March 31, 2023, IPL had $21 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): 2023 2022 Maximum outstanding aggregate cash proceeds $89 $36 Average outstanding aggregate cash proceeds 58 4 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 94 132 Receivables sold to third party 255 277 Less: cash proceeds 89 80 Deferred proceeds 166 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $153 $185 As of March 31, 2023, outstanding receivables past due under the Receivables Agreement were $26 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions): 2023 2022 Collections $591 $561 Write-offs, net of recoveries 2 2
IPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three months ended March 31, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable, which originated in 2022, were $5 million, $3 million and $2 million, respectively. NOTE 4(b) - 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. In March 2023, IPL amended and extended through March 2024 the purchase commitment from the third party to which it sells its receivables. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of March 31, 2023, IPL had $21 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): 2023 2022 Maximum outstanding aggregate cash proceeds $89 $36 Average outstanding aggregate cash proceeds 58 4 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 94 132 Receivables sold to third party 255 277 Less: cash proceeds 89 80 Deferred proceeds 166 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $153 $185 As of March 31, 2023, outstanding receivables past due under the Receivables Agreement were $26 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions): 2023 2022 Collections $591 $561 Write-offs, net of recoveries 2 2
WPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three months ended March 31, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable, which originated in 2022, were $5 million, $3 million and $2 million, respectively.

Investments

Investments	3 Months Ended
	Mar. 31, 2023
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): 2023 2022 ATC Holdings ($13) ($11) Other (4) (4) ($17) ($15)

Common Equity

Common Equity	3 Months Ended
	Mar. 31, 2023
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, 2023 251,134,966 Shareowner Direct Plan 118,488 Equity-based compensation plans 134,334 Shares outstanding, March 31, 2023 251,387,788 Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Loss Trust Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $6,276 Net income attributable to Alliant Energy common shareowners 163 163 Common stock dividends ($0.4525 per share) (113) (113) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other (3) (3) Other comprehensive loss, net of tax (1) (1) Ending balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $6,328 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 72 72 Common stock dividends (70) (70) Ending balance, March 31, 2023 $33 $2,807 $970 $3,810 Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $3,775 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $3,491 Net income 88 88 Common stock dividends (46) (46) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $66 $2,413 $1,234 $3,713 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
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, 2023 251,134,966 Shareowner Direct Plan 118,488 Equity-based compensation plans 134,334 Shares outstanding, March 31, 2023 251,387,788 Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Loss Trust Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $6,276 Net income attributable to Alliant Energy common shareowners 163 163 Common stock dividends ($0.4525 per share) (113) (113) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other (3) (3) Other comprehensive loss, net of tax (1) (1) Ending balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $6,328 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 72 72 Common stock dividends (70) (70) Ending balance, March 31, 2023 $33 $2,807 $970 $3,810 Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $3,775 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $3,491 Net income 88 88 Common stock dividends (46) (46) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $66 $2,413 $1,234 $3,713 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
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, 2023 251,134,966 Shareowner Direct Plan 118,488 Equity-based compensation plans 134,334 Shares outstanding, March 31, 2023 251,387,788 Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Loss Trust Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $6,276 Net income attributable to Alliant Energy common shareowners 163 163 Common stock dividends ($0.4525 per share) (113) (113) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other (3) (3) Other comprehensive loss, net of tax (1) (1) Ending balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $6,328 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 72 72 Common stock dividends (70) (70) Ending balance, March 31, 2023 $33 $2,807 $970 $3,810 Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $3,775 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $3,491 Net income 88 88 Common stock dividends (46) (46) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $66 $2,413 $1,234 $3,713 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

Debt

Debt	3 Months Ended
	Mar. 31, 2023
Debt [Line Items]
Debt	DEBT NOTE 7(a) Short-term Debt - In March 2023, Alliant Energy, IPL and WPL extended their single credit facility agreement, which currently expires in December 2027, and reallocated credit facility capacity amounts to $450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 million for WPL, within the $1 billion total commitment. 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, 2023 Alliant Energy IPL WPL Amount outstanding $60 $— $60 Weighted average interest rates 5.1% N/A 5.1% Available credit facility capacity $940 $250 $240 Alliant Energy WPL Three Months Ended March 31 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $349 $252 Average amount outstanding (based on daily outstanding balances) $574 $443 $304 $205 Weighted average interest rates 4.8% 0.3% 4.8% 0.3% In January 2023, AEF received $50 million of proceeds from its December 2022 term loan credit agreement, which was classified as “Other short-term borrowings” on Alliant Energy’s balance sheet as of March 31, 2023. NOTE 7(b) Long-term Debt - In March 2023, WPL issued $300 million of 4.95% debentures due 2033. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds will be allocated or disbursed for the development and acquisition of WPL’s solar EGUs. Convertible Senior Notes - In March 2023, Alliant Energy issued $575 million of 3.875% convertible senior notes (the Notes), which are senior unsecured obligations, and used the net proceeds from the issuance for general corporate purposes. The Notes will mature on March 15, 2026 unless earlier converted or repurchased, and no sinking fund is provided for the Notes. Alliant Energy may not redeem the Notes prior to the maturity date. Holders may convert their Notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2025 only under the following circumstances: • during any calendar quarter commencing after the calendar quarter ending on June 30, 2023 (and only during such calendar quarter), if the last reported sale price of Alliant Energy’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day during such period; • during the 5 business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $1,000 principal amount of Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of Alliant Energy’s common stock and the conversion rate on each such trading day; or • upon the occurrence of specified corporate events. On or after December 15, 2025 until the close of business on the business day immediately preceding the maturity date, holders may convert all or any portion of their Notes at any time, regardless of the foregoing circumstances. Upon conversion of the Notes, Alliant Energy will pay cash up to the aggregate principal amount of the Notes to be converted and pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the Notes being converted. The conversion rate will initially be 15.5461 shares of common stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of approximately $64.32 per share of Alliant Energy’s common stock). The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, Alliant Energy will, in certain circumstances, increase the conversion rate for a holder who elects to convert its Notes in connection with such a corporate event. If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the Notes may require Alliant Energy to repurchase for cash all or any portion of its Notes at a repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.
IPL [Member]
Debt [Line Items]
Debt	DEBT NOTE 7(a) Short-term Debt - In March 2023, Alliant Energy, IPL and WPL extended their single credit facility agreement, which currently expires in December 2027, and reallocated credit facility capacity amounts to $450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 million for WPL, within the $1 billion total commitment. 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, 2023 Alliant Energy IPL WPL Amount outstanding $60 $— $60 Weighted average interest rates 5.1% N/A 5.1% Available credit facility capacity $940 $250 $240 Alliant Energy WPL Three Months Ended March 31 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $349 $252 Average amount outstanding (based on daily outstanding balances) $574 $443 $304 $205 Weighted average interest rates 4.8% 0.3% 4.8% 0.3%
WPL [Member]
Debt [Line Items]
Debt	DEBT NOTE 7(a) Short-term Debt - In March 2023, Alliant Energy, IPL and WPL extended their single credit facility agreement, which currently expires in December 2027, and reallocated credit facility capacity amounts to $450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 million for WPL, within the $1 billion total commitment. 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, 2023 Alliant Energy IPL WPL Amount outstanding $60 $— $60 Weighted average interest rates 5.1% N/A 5.1% Available credit facility capacity $940 $250 $240 Alliant Energy WPL Three Months Ended March 31 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $349 $252 Average amount outstanding (based on daily outstanding balances) $574 $443 $304 $205 Weighted average interest rates 4.8% 0.3% 4.8% 0.3% In January 2023, AEF received $50 million of proceeds from its December 2022 term loan credit agreement, which was classified as “Other short-term borrowings” on Alliant Energy’s balance sheet as of March 31, 2023. NOTE 7(b) Long-term Debt - In March 2023, WPL issued $300 million of 4.95% debentures due 2033. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds will be allocated or disbursed for the development and acquisition of WPL’s solar EGUs.

Revenues

Revenues	3 Months Ended
	Mar. 31, 2023
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 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $285 $293 $143 $150 $142 $143 Retail - commercial 185 188 112 118 73 70 Retail - industrial 216 211 107 111 109 100 Wholesale 46 47 12 15 34 32 Bulk power and other 36 34 14 6 22 28 Total Electric Utility 768 773 388 400 380 373 Gas Utility: Retail - residential 167 158 93 85 74 73 Retail - commercial 88 82 44 40 44 42 Retail - industrial 7 8 4 5 3 3 Transportation/other 14 14 9 9 5 5 Total Gas Utility 276 262 150 139 126 123 Other Utility: Steam 10 9 10 9 — — Other utility 1 2 1 2 — — Total Other Utility 11 11 11 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $1,077 $1,068 $549 $550 $506 $496
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 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $285 $293 $143 $150 $142 $143 Retail - commercial 185 188 112 118 73 70 Retail - industrial 216 211 107 111 109 100 Wholesale 46 47 12 15 34 32 Bulk power and other 36 34 14 6 22 28 Total Electric Utility 768 773 388 400 380 373 Gas Utility: Retail - residential 167 158 93 85 74 73 Retail - commercial 88 82 44 40 44 42 Retail - industrial 7 8 4 5 3 3 Transportation/other 14 14 9 9 5 5 Total Gas Utility 276 262 150 139 126 123 Other Utility: Steam 10 9 10 9 — — Other utility 1 2 1 2 — — Total Other Utility 11 11 11 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $1,077 $1,068 $549 $550 $506 $496
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 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $285 $293 $143 $150 $142 $143 Retail - commercial 185 188 112 118 73 70 Retail - industrial 216 211 107 111 109 100 Wholesale 46 47 12 15 34 32 Bulk power and other 36 34 14 6 22 28 Total Electric Utility 768 773 388 400 380 373 Gas Utility: Retail - residential 167 158 93 85 74 73 Retail - commercial 88 82 44 40 44 42 Retail - industrial 7 8 4 5 3 3 Transportation/other 14 14 9 9 5 5 Total Gas Utility 276 262 150 139 126 123 Other Utility: Steam 10 9 10 9 — — Other utility 1 2 1 2 — — Total Other Utility 11 11 11 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $1,077 $1,068 $549 $550 $506 $496

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2023
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. Alliant Energy IPL WPL 2023 2022 2023 2022 2023 2022 Overall income tax rate (1%) 4% (18%) (14%) 12% 19% Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2023, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2043 $535 $12 $1 Federal tax credits 2027-2043 698 468 218
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. Alliant Energy IPL WPL 2023 2022 2023 2022 2023 2022 Overall income tax rate (1%) 4% (18%) (14%) 12% 19% Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2023, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2043 $535 $12 $1 Federal tax credits 2027-2043 698 468 218
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. Alliant Energy IPL WPL 2023 2022 2023 2022 2023 2022 Overall income tax rate (1%) 4% (18%) (14%) 12% 19% Deferred Tax Assets and Liabilities - Carryforwards - At March 31, 2023, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2043 $535 $12 $1 Federal tax credits 2027-2043 698 468 218

Benefit Plans

Benefit Plans	3 Months Ended
	Mar. 31, 2023
Benefit Plans	BENEFIT PLANS NOTE 10(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 2023 2022 2023 2022 Service cost $1 $2 $1 $1 Interest cost 11 9 2 1 Expected return on plan assets (13) (17) (1) (1) Amortization of actuarial loss 7 8 — 1 $6 $2 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2023 2022 2023 2022 Service cost $1 $2 $— $— Interest cost 5 4 1 1 Expected return on plan assets (7) (8) (1) (1) Amortization of actuarial loss 3 3 — — $2 $1 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2023 2022 2023 2022 Service cost $— $1 $— $— Interest cost 5 4 1 1 Expected return on plan assets (5) (8) — — Amortization of actuarial loss 3 4 — — $3 $1 $1 $1 NOTE 10(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 2023 2022 2023 2022 2023 2022 Compensation expense $3 $4 $2 $2 $1 $2 Income tax benefits 1 1 — 1 — — As of March 31, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $18 million, $9 million and $8 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, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing plans 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 100,055 $55.68 Performance restricted stock units 114,325 52.73 Restricted stock units 99,941 52.78 As of March 31, 2023, 170,209 shares were included in the calculation of diluted EPS related to the nonvested equity awards.
IPL [Member]
Benefit Plans	BENEFIT PLANS NOTE 10(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 2023 2022 2023 2022 Service cost $1 $2 $1 $1 Interest cost 11 9 2 1 Expected return on plan assets (13) (17) (1) (1) Amortization of actuarial loss 7 8 — 1 $6 $2 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2023 2022 2023 2022 Service cost $1 $2 $— $— Interest cost 5 4 1 1 Expected return on plan assets (7) (8) (1) (1) Amortization of actuarial loss 3 3 — — $2 $1 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2023 2022 2023 2022 Service cost $— $1 $— $— Interest cost 5 4 1 1 Expected return on plan assets (5) (8) — — Amortization of actuarial loss 3 4 — — $3 $1 $1 $1 NOTE 10(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 2023 2022 2023 2022 2023 2022 Compensation expense $3 $4 $2 $2 $1 $2 Income tax benefits 1 1 — 1 — — As of March 31, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $18 million, $9 million and $8 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, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing plans 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 100,055 $55.68 Performance restricted stock units 114,325 52.73 Restricted stock units 99,941 52.78 As of March 31, 2023, 170,209 shares were included in the calculation of diluted EPS related to the nonvested equity awards.
WPL [Member]
Benefit Plans	BENEFIT PLANS NOTE 10(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 2023 2022 2023 2022 Service cost $1 $2 $1 $1 Interest cost 11 9 2 1 Expected return on plan assets (13) (17) (1) (1) Amortization of actuarial loss 7 8 — 1 $6 $2 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2023 2022 2023 2022 Service cost $1 $2 $— $— Interest cost 5 4 1 1 Expected return on plan assets (7) (8) (1) (1) Amortization of actuarial loss 3 3 — — $2 $1 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2023 2022 2023 2022 Service cost $— $1 $— $— Interest cost 5 4 1 1 Expected return on plan assets (5) (8) — — Amortization of actuarial loss 3 4 — — $3 $1 $1 $1 NOTE 10(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 2023 2022 2023 2022 2023 2022 Compensation expense $3 $4 $2 $2 $1 $2 Income tax benefits 1 1 — 1 — — As of March 31, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $18 million, $9 million and $8 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, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing plans 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 100,055 $55.68 Performance restricted stock units 114,325 52.73 Restricted stock units 99,941 52.78 As of March 31, 2023, 170,209 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2023
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2023, 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): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 922 2023-2025 3,276 2023 209,102 2023-2032 662 2023 IPL 391 2023-2025 1,338 2023 101,863 2023-2030 325 2023 WPL 531 2023 1,938 2023 107,239 2023-2032 337 2023 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 $28 $111 $17 $69 $11 $42 Non-current derivative assets 94 126 52 69 42 57 Current derivative liabilities 65 59 26 40 39 19 Non-current derivative liabilities 30 20 8 6 22 14 During the three months ended March 31, 2023, Alliant Energy’s, IPL’s and WPL’s current derivative assets decreased primarily due to settlements of natural gas, FTR and electricity contracts. Alliant Energy’s and WPL’s derivative liabilities increased primarily due to lower natural gas prices. IPL’s current derivative liabilities decreased primarily due to settlements of natural gas contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/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 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, 2023 and December 31, 2022, 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, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions): Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2023 Derivative assets $122 $89 $69 $51 $53 $38 Derivative liabilities 95 62 34 16 61 46 December 31, 2022 Derivative assets 237 193 138 108 99 85 Derivative liabilities 79 35 46 16 33 19 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. Interest Rate Derivative - In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026 to mitigate interest rate risk. Under the terms of the swap, AEF exchanged a variable interest rate for a fixed interest rate of 3.93% on a portion of its variable-rate term loan borrowings. The related interest rate derivative was valued based on quoted prices that utilize current market interest rate forecasts. As of March 31, 2023, $1 million of non-current interest rate derivative liabilities were recorded in “Other liabilities” on Alliant Energy’s balance sheet. This interest rate derivative was designated as a cash flow hedge, with changes in fair value recorded as other comprehensive income/loss. As of March 31, 2023, accumulated other comprehensive loss included $1 million of losses related to the interest rate swap. For the three months ended March 31, 2023, a $1 million reduction to interest expense was recorded in Alliant Energy’s income statement related to the interest rate swap.
IPL [Member]
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of March 31, 2023, 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): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 922 2023-2025 3,276 2023 209,102 2023-2032 662 2023 IPL 391 2023-2025 1,338 2023 101,863 2023-2030 325 2023 WPL 531 2023 1,938 2023 107,239 2023-2032 337 2023 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 $28 $111 $17 $69 $11 $42 Non-current derivative assets 94 126 52 69 42 57 Current derivative liabilities 65 59 26 40 39 19 Non-current derivative liabilities 30 20 8 6 22 14 During the three months ended March 31, 2023, Alliant Energy’s, IPL’s and WPL’s current derivative assets decreased primarily due to settlements of natural gas, FTR and electricity contracts. Alliant Energy’s and WPL’s derivative liabilities increased primarily due to lower natural gas prices. IPL’s current derivative liabilities decreased primarily due to settlements of natural gas contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/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 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, 2023 and December 31, 2022, 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, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions): Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2023 Derivative assets $122 $89 $69 $51 $53 $38 Derivative liabilities 95 62 34 16 61 46 December 31, 2022 Derivative assets 237 193 138 108 99 85 Derivative liabilities 79 35 46 16 33 19 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, 2023, 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): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 922 2023-2025 3,276 2023 209,102 2023-2032 662 2023 IPL 391 2023-2025 1,338 2023 101,863 2023-2030 325 2023 WPL 531 2023 1,938 2023 107,239 2023-2032 337 2023 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 $28 $111 $17 $69 $11 $42 Non-current derivative assets 94 126 52 69 42 57 Current derivative liabilities 65 59 26 40 39 19 Non-current derivative liabilities 30 20 8 6 22 14 During the three months ended March 31, 2023, Alliant Energy’s, IPL’s and WPL’s current derivative assets decreased primarily due to settlements of natural gas, FTR and electricity contracts. Alliant Energy’s and WPL’s derivative liabilities increased primarily due to lower natural gas prices. IPL’s current derivative liabilities decreased primarily due to settlements of natural gas contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/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 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, 2023 and December 31, 2022, 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, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions): Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2023 Derivative assets $122 $89 $69 $51 $53 $38 Derivative liabilities 95 62 34 16 61 46 December 31, 2022 Derivative assets 237 193 138 108 99 85 Derivative liabilities 79 35 46 16 33 19 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, 2023
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, 2023 December 31, 2022 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 $148 $148 $— $— $148 $10 $10 $— $— $10 Commodity derivatives 122 — 116 6 122 237 — 206 31 237 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 95 — 84 11 95 79 — 67 12 79 Interest rate derivatives 1 — 1 — 1 — — — — — Long-term debt (incl. current maturities) 8,940 — 8,461 1 8,462 8,076 — 7,338 1 7,339 IPL March 31, 2023 December 31, 2022 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 $30 $30 $— $— $30 $10 $10 $— $— $10 Commodity derivatives 69 — 63 6 69 138 — 111 27 138 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 34 — 28 6 34 46 — 35 11 46 Long-term debt 3,647 — 3,335 — 3,335 3,646 — 3,228 — 3,228 WPL March 31, 2023 December 31, 2022 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 $83 $83 $— $— $83 $— $— $— $— $— Commodity derivatives 53 — 53 — 53 99 — 95 4 99 Liabilities: Commodity derivatives 61 — 56 5 61 33 — 32 1 33 Long-term debt 3,067 — 2,939 — 2,939 2,770 — 2,542 — 2,542 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 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (4) (6) — — Settlements (a) (20) (13) (32) 13 Ending balance, March 31 ($5) $10 $153 $227 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) ($5) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (4) — — Settlements (a) (17) (7) (32) 13 Ending balance, March 31 $— $7 $153 $227 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 $1 ($4) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2023 2022 Beginning balance, January 1 $3 $11 Total net losses included in changes in net assets (realized/unrealized) (5) (2) Settlements (3) (6) Ending balance, March 31 ($5) $3 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) ($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 (liabilities) as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2023 ($10) $5 ($4) $4 ($6) $1 December 31, 2022 (10) 29 (9) 25 (1) 4
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, 2023 December 31, 2022 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 $148 $148 $— $— $148 $10 $10 $— $— $10 Commodity derivatives 122 — 116 6 122 237 — 206 31 237 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 95 — 84 11 95 79 — 67 12 79 Interest rate derivatives 1 — 1 — 1 — — — — — Long-term debt (incl. current maturities) 8,940 — 8,461 1 8,462 8,076 — 7,338 1 7,339 IPL March 31, 2023 December 31, 2022 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 $30 $30 $— $— $30 $10 $10 $— $— $10 Commodity derivatives 69 — 63 6 69 138 — 111 27 138 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 34 — 28 6 34 46 — 35 11 46 Long-term debt 3,647 — 3,335 — 3,335 3,646 — 3,228 — 3,228 WPL March 31, 2023 December 31, 2022 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 $83 $83 $— $— $83 $— $— $— $— $— Commodity derivatives 53 — 53 — 53 99 — 95 4 99 Liabilities: Commodity derivatives 61 — 56 5 61 33 — 32 1 33 Long-term debt 3,067 — 2,939 — 2,939 2,770 — 2,542 — 2,542 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 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (4) (6) — — Settlements (a) (20) (13) (32) 13 Ending balance, March 31 ($5) $10 $153 $227 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) ($5) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (4) — — Settlements (a) (17) (7) (32) 13 Ending balance, March 31 $— $7 $153 $227 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 $1 ($4) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2023 2022 Beginning balance, January 1 $3 $11 Total net losses included in changes in net assets (realized/unrealized) (5) (2) Settlements (3) (6) Ending balance, March 31 ($5) $3 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) ($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 (liabilities) as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2023 ($10) $5 ($4) $4 ($6) $1 December 31, 2022 (10) 29 (9) 25 (1) 4
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, 2023 December 31, 2022 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 $148 $148 $— $— $148 $10 $10 $— $— $10 Commodity derivatives 122 — 116 6 122 237 — 206 31 237 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 95 — 84 11 95 79 — 67 12 79 Interest rate derivatives 1 — 1 — 1 — — — — — Long-term debt (incl. current maturities) 8,940 — 8,461 1 8,462 8,076 — 7,338 1 7,339 IPL March 31, 2023 December 31, 2022 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 $30 $30 $— $— $30 $10 $10 $— $— $10 Commodity derivatives 69 — 63 6 69 138 — 111 27 138 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 34 — 28 6 34 46 — 35 11 46 Long-term debt 3,647 — 3,335 — 3,335 3,646 — 3,228 — 3,228 WPL March 31, 2023 December 31, 2022 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 $83 $83 $— $— $83 $— $— $— $— $— Commodity derivatives 53 — 53 — 53 99 — 95 4 99 Liabilities: Commodity derivatives 61 — 56 5 61 33 — 32 1 33 Long-term debt 3,067 — 2,939 — 2,939 2,770 — 2,542 — 2,542 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 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (4) (6) — — Settlements (a) (20) (13) (32) 13 Ending balance, March 31 ($5) $10 $153 $227 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) ($5) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (4) — — Settlements (a) (17) (7) (32) 13 Ending balance, March 31 $— $7 $153 $227 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 $1 ($4) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2023 2022 Beginning balance, January 1 $3 $11 Total net losses included in changes in net assets (realized/unrealized) (5) (2) Settlements (3) (6) Ending balance, March 31 ($5) $3 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) ($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 (liabilities) as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2023 ($10) $5 ($4) $4 ($6) $1 December 31, 2022 (10) 29 (9) 25 (1) 4

Commitments And Contingencies

Commitments And Contingencies	3 Months Ended
	Mar. 31, 2023
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 13(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including IPL’s and WPL’s expansion of solar generation. At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $252 million, $40 million and $212 million, respectively. NOTE 13(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, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,280 $565 $715 Coal 175 89 86 Other (a) 113 53 26 $1,568 $707 $827 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2023. NOTE 13(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, 2023, the currently known partnership obligations for the abandonment obligations are estimated at $58 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 $58 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, 2023 and December 31, 2022, 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. Whiting Petroleum completed a business combination with Oasis Petroleum Inc. in July 2022. The combined operations are now known as Chord Energy Corporation. The business combination is not expected to affect the scope of the Whiting Petroleum affiliate’s obligations to Alliant Energy or Alliant Energy’s related 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 $59 million as of March 31, 2023 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, 2023 and December 31, 2022. NOTE 13(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, 2023, 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): Alliant Energy IPL WPL Range of estimated future costs $10 - $37 $6 - $12 $4 - $25 Current and non-current environmental liabilities $18 $8 $10 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: Cross-State Air Pollution Rule, 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 13(e) MISO Transmission Owner Return on Equity Complaints - A group of stakeholders, including MISO cooperative and municipal utilities, previously filed complaints with the Federal Energy Regulatory Commission (FERC) requesting a reduction to the base return on equity authorized for MISO transmission owners, including ITC Midwest LLC and ATC. In 2019, FERC issued an order on the previously filed complaints and reduced the base return on equity authorized for the MISO transmission owners to 9.88% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2020, FERC issued orders in response to various rehearing requests and increased the base return on equity authorized for the MISO transmission owners from 9.88% to 10.02% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In August 2022, the U.S. Court of Appeals for the District of Columbia Circuit vacated FERC’s prior orders that established the base return on equity authorized for the MISO transmission owners and remanded the cases to FERC for further proceedings, which may result in additional changes to the base return on equity authorized for
IPL [Member]
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 13(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including IPL’s and WPL’s expansion of solar generation. At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $252 million, $40 million and $212 million, respectively. NOTE 13(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, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,280 $565 $715 Coal 175 89 86 Other (a) 113 53 26 $1,568 $707 $827 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2023. NOTE 13(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, 2023, the currently known partnership obligations for the abandonment obligations are estimated at $58 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 $58 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, 2023 and December 31, 2022, 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. Whiting Petroleum completed a business combination with Oasis Petroleum Inc. in July 2022. The combined operations are now known as Chord Energy Corporation. The business combination is not expected to affect the scope of the Whiting Petroleum affiliate’s obligations to Alliant Energy or Alliant Energy’s related 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 $59 million as of March 31, 2023 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, 2023 and December 31, 2022. NOTE 13(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, 2023, 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): Alliant Energy IPL WPL Range of estimated future costs $10 - $37 $6 - $12 $4 - $25 Current and non-current environmental liabilities $18 $8 $10 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: Cross-State Air Pollution Rule, 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 13(e) MISO Transmission Owner Return on Equity Complaints - A group of stakeholders, including MISO cooperative and municipal utilities, previously filed complaints with the Federal Energy Regulatory Commission (FERC) requesting a reduction to the base return on equity authorized for MISO transmission owners, including ITC Midwest LLC and ATC. In 2019, FERC issued an order on the previously filed complaints and reduced the base return on equity authorized for the MISO transmission owners to 9.88% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2020, FERC issued orders in response to various rehearing requests and increased the base return on equity authorized for the MISO transmission owners from 9.88% to 10.02% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In August 2022, the U.S. Court of Appeals for the District of Columbia Circuit vacated FERC’s prior orders that established the base return on equity authorized for the MISO transmission owners and remanded the cases to FERC for further proceedings, which may result in additional changes to the base return on equity authorized for
WPL [Member]
Commitments and Contingencies Disclosure	COMMITMENTS AND CONTINGENCIES NOTE 13(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including IPL’s and WPL’s expansion of solar generation. At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $252 million, $40 million and $212 million, respectively. NOTE 13(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, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,280 $565 $715 Coal 175 89 86 Other (a) 113 53 26 $1,568 $707 $827 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2023. NOTE 13(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, 2023, the currently known partnership obligations for the abandonment obligations are estimated at $58 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 $58 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, 2023 and December 31, 2022, 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. Whiting Petroleum completed a business combination with Oasis Petroleum Inc. in July 2022. The combined operations are now known as Chord Energy Corporation. The business combination is not expected to affect the scope of the Whiting Petroleum affiliate’s obligations to Alliant Energy or Alliant Energy’s related 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 $59 million as of March 31, 2023 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, 2023 and December 31, 2022. NOTE 13(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, 2023, 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): Alliant Energy IPL WPL Range of estimated future costs $10 - $37 $6 - $12 $4 - $25 Current and non-current environmental liabilities $18 $8 $10 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: Cross-State Air Pollution Rule, 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 13(e) MISO Transmission Owner Return on Equity Complaints - A group of stakeholders, including MISO cooperative and municipal utilities, previously filed complaints with the Federal Energy Regulatory Commission (FERC) requesting a reduction to the base return on equity authorized for MISO transmission owners, including ITC Midwest LLC and ATC. In 2019, FERC issued an order on the previously filed complaints and reduced the base return on equity authorized for the MISO transmission owners to 9.88% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2020, FERC issued orders in response to various rehearing requests and increased the base return on equity authorized for the MISO transmission owners from 9.88% to 10.02% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In August 2022, the U.S. Court of Appeals for the District of Columbia Circuit vacated FERC’s prior orders that established the base return on equity authorized for the MISO transmission owners and remanded the cases to FERC for further proceedings, which may result in additional changes to the base return on equity authorized for

Segments Of Business

Segments Of Business	3 Months Ended
	Mar. 31, 2023
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, 2023 Revenues $768 $276 $11 $1,055 $22 $1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 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 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $388 $150 $11 $549 Operating income 66 27 3 96 Net income 72 Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income 87 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $380 $126 $— $506 Operating income 97 23 1 121 Net income 88 Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92
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, 2023 Revenues $768 $276 $11 $1,055 $22 $1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 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 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $388 $150 $11 $549 Operating income 66 27 3 96 Net income 72 Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income 87 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $380 $126 $— $506 Operating income 97 23 1 121 Net income 88 Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92
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, 2023 Revenues $768 $276 $11 $1,055 $22 $1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 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 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $388 $150 $11 $549 Operating income 66 27 3 96 Net income 72 Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income 87 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $380 $126 $— $506 Operating income 97 23 1 121 Net income 88 Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92

Related Parties

Related Parties	3 Months Ended
	Mar. 31, 2023
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 2023 2022 2023 2022 Corporate Services billings $40 $40 $36 $36 Sales credited 7 — 13 18 Purchases billed 93 94 15 22 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2023 December 31, 2022 March 31, 2023 December 31, 2022 Net payables to Corporate Services $110 $103 $65 $56 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): 2023 2022 ATC billings to WPL $34 $34 WPL billings to ATC 6 3 WPL owed ATC net amounts of $9 million as of March 31, 2023 and $10 million as of December 31, 2022.
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 2023 2022 2023 2022 Corporate Services billings $40 $40 $36 $36 Sales credited 7 — 13 18 Purchases billed 93 94 15 22 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2023 December 31, 2022 March 31, 2023 December 31, 2022 Net payables to Corporate Services $110 $103 $65 $56
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 2023 2022 2023 2022 Corporate Services billings $40 $40 $36 $36 Sales credited 7 — 13 18 Purchases billed 93 94 15 22 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2023 December 31, 2022 March 31, 2023 December 31, 2022 Net payables to Corporate Services $110 $103 $65 $56 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): 2023 2022 ATC billings to WPL $34 $34 WPL billings to ATC 6 3 WPL owed ATC net amounts of $9 million as of March 31, 2023 and $10 million as of December 31, 2022.

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2023
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 2022 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 and Cash Equivalents	At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $148 million, $30 million and $83 million of money market fund investments, respectively, with interest rates of 5%.
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 2022 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 and Cash Equivalents	At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $148 million, $30 million and $83 million of money market fund investments, respectively, with interest rates of 5%.
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 2022 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 and Cash Equivalents	At March 31, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $148 million, $30 million and $83 million of money market fund investments, respectively, with interest rates of 5%.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2023
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 $942 $929 $857 $848 $85 $81 Pension and OPEB costs 385 392 193 197 192 195 Asset retirement obligations 156 151 115 110 41 41 Commodity cost recovery 152 160 4 1 148 159 Derivatives 101 84 37 48 64 36 Assets retired early 67 70 51 53 16 17 IPL’s Duane Arnold Energy Center PPA amendment 60 66 60 66 — — WPL’s Western Wisconsin gas distribution expansion investments 48 48 — — 48 48 Other 169 146 66 63 103 83 $2,080 $2,046 $1,383 $1,386 $697 $660
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 $575 $579 $302 $303 $273 $276 Cost of removal obligations 403 398 261 259 142 139 Derivatives 117 210 64 115 53 95 Electric transmission cost recovery 26 20 19 10 7 10 WPL’s West Riverside liquidated damages 24 32 — — 24 32 Commodity cost recovery 22 40 8 38 14 2 Other 64 45 43 29 21 16 $1,231 $1,324 $697 $754 $534 $570
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 $942 $929 $857 $848 $85 $81 Pension and OPEB costs 385 392 193 197 192 195 Asset retirement obligations 156 151 115 110 41 41 Commodity cost recovery 152 160 4 1 148 159 Derivatives 101 84 37 48 64 36 Assets retired early 67 70 51 53 16 17 IPL’s Duane Arnold Energy Center PPA amendment 60 66 60 66 — — WPL’s Western Wisconsin gas distribution expansion investments 48 48 — — 48 48 Other 169 146 66 63 103 83 $2,080 $2,046 $1,383 $1,386 $697 $660
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 $575 $579 $302 $303 $273 $276 Cost of removal obligations 403 398 261 259 142 139 Derivatives 117 210 64 115 53 95 Electric transmission cost recovery 26 20 19 10 7 10 WPL’s West Riverside liquidated damages 24 32 — — 24 32 Commodity cost recovery 22 40 8 38 14 2 Other 64 45 43 29 21 16 $1,231 $1,324 $697 $754 $534 $570
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 $942 $929 $857 $848 $85 $81 Pension and OPEB costs 385 392 193 197 192 195 Asset retirement obligations 156 151 115 110 41 41 Commodity cost recovery 152 160 4 1 148 159 Derivatives 101 84 37 48 64 36 Assets retired early 67 70 51 53 16 17 IPL’s Duane Arnold Energy Center PPA amendment 60 66 60 66 — — WPL’s Western Wisconsin gas distribution expansion investments 48 48 — — 48 48 Other 169 146 66 63 103 83 $2,080 $2,046 $1,383 $1,386 $697 $660
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 $575 $579 $302 $303 $273 $276 Cost of removal obligations 403 398 261 259 142 139 Derivatives 117 210 64 115 53 95 Electric transmission cost recovery 26 20 19 10 7 10 WPL’s West Riverside liquidated damages 24 32 — — 24 32 Commodity cost recovery 22 40 8 38 14 2 Other 64 45 43 29 21 16 $1,231 $1,324 $697 $754 $534 $570

Receivables (Tables)

Receivables (Tables)	3 Months Ended
	Mar. 31, 2023
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): 2023 2022 Maximum outstanding aggregate cash proceeds $89 $36 Average outstanding aggregate cash proceeds 58 4
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, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 94 132 Receivables sold to third party 255 277 Less: cash proceeds 89 80 Deferred proceeds 166 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $153 $185
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): 2023 2022 Collections $591 $561 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): 2023 2022 Maximum outstanding aggregate cash proceeds $89 $36 Average outstanding aggregate cash proceeds 58 4
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, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 94 132 Receivables sold to third party 255 277 Less: cash proceeds 89 80 Deferred proceeds 166 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $153 $185
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): 2023 2022 Collections $591 $561 Write-offs, net of recoveries 2 2

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2023
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): 2023 2022 ATC Holdings ($13) ($11) Other (4) (4) ($17) ($15)

Common Equity (Tables)

Common Equity (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 251,134,966 Shareowner Direct Plan 118,488 Equity-based compensation plans 134,334 Shares outstanding, March 31, 2023 251,387,788
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Loss Trust Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $6,276 Net income attributable to Alliant Energy common shareowners 163 163 Common stock dividends ($0.4525 per share) (113) (113) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other (3) (3) Other comprehensive loss, net of tax (1) (1) Ending balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $6,328 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 72 72 Common stock dividends (70) (70) Ending balance, March 31, 2023 $33 $2,807 $970 $3,810 Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $3,775 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $3,491 Net income 88 88 Common stock dividends (46) (46) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $66 $2,413 $1,234 $3,713 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
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 Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Loss Trust Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $6,276 Net income attributable to Alliant Energy common shareowners 163 163 Common stock dividends ($0.4525 per share) (113) (113) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other (3) (3) Other comprehensive loss, net of tax (1) (1) Ending balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $6,328 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 72 72 Common stock dividends (70) (70) Ending balance, March 31, 2023 $33 $2,807 $970 $3,810 Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $3,775 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $3,491 Net income 88 88 Common stock dividends (46) (46) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $66 $2,413 $1,234 $3,713 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
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 Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Loss Trust Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $6,276 Net income attributable to Alliant Energy common shareowners 163 163 Common stock dividends ($0.4525 per share) (113) (113) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other (3) (3) Other comprehensive loss, net of tax (1) (1) Ending balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $6,328 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 72 72 Common stock dividends (70) (70) Ending balance, March 31, 2023 $33 $2,807 $970 $3,810 Three Months Ended March 31, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 87 87 Common stock dividends (81) (81) Ending balance, March 31, 2022 $33 $2,807 $935 $3,775 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $3,491 Net income 88 88 Common stock dividends (46) (46) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $66 $2,413 $1,234 $3,713 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

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 Alliant Energy IPL WPL Amount outstanding $60 $— $60 Weighted average interest rates 5.1% N/A 5.1% Available credit facility capacity $940 $250 $240 Alliant Energy WPL Three Months Ended March 31 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $349 $252 Average amount outstanding (based on daily outstanding balances) $574 $443 $304 $205 Weighted average interest rates 4.8% 0.3% 4.8% 0.3%
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, 2023 Alliant Energy IPL WPL Amount outstanding $60 $— $60 Weighted average interest rates 5.1% N/A 5.1% Available credit facility capacity $940 $250 $240 Alliant Energy WPL Three Months Ended March 31 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $349 $252 Average amount outstanding (based on daily outstanding balances) $574 $443 $304 $205 Weighted average interest rates 4.8% 0.3% 4.8% 0.3%
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, 2023 Alliant Energy IPL WPL Amount outstanding $60 $— $60 Weighted average interest rates 5.1% N/A 5.1% Available credit facility capacity $940 $250 $240 Alliant Energy WPL Three Months Ended March 31 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $349 $252 Average amount outstanding (based on daily outstanding balances) $574 $443 $304 $205 Weighted average interest rates 4.8% 0.3% 4.8% 0.3%

Revenues (Tables)

Revenues (Tables)	3 Months Ended
	Mar. 31, 2023
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 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $285 $293 $143 $150 $142 $143 Retail - commercial 185 188 112 118 73 70 Retail - industrial 216 211 107 111 109 100 Wholesale 46 47 12 15 34 32 Bulk power and other 36 34 14 6 22 28 Total Electric Utility 768 773 388 400 380 373 Gas Utility: Retail - residential 167 158 93 85 74 73 Retail - commercial 88 82 44 40 44 42 Retail - industrial 7 8 4 5 3 3 Transportation/other 14 14 9 9 5 5 Total Gas Utility 276 262 150 139 126 123 Other Utility: Steam 10 9 10 9 — — Other utility 1 2 1 2 — — Total Other Utility 11 11 11 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $1,077 $1,068 $549 $550 $506 $496
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 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $285 $293 $143 $150 $142 $143 Retail - commercial 185 188 112 118 73 70 Retail - industrial 216 211 107 111 109 100 Wholesale 46 47 12 15 34 32 Bulk power and other 36 34 14 6 22 28 Total Electric Utility 768 773 388 400 380 373 Gas Utility: Retail - residential 167 158 93 85 74 73 Retail - commercial 88 82 44 40 44 42 Retail - industrial 7 8 4 5 3 3 Transportation/other 14 14 9 9 5 5 Total Gas Utility 276 262 150 139 126 123 Other Utility: Steam 10 9 10 9 — — Other utility 1 2 1 2 — — Total Other Utility 11 11 11 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $1,077 $1,068 $549 $550 $506 $496
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 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $285 $293 $143 $150 $142 $143 Retail - commercial 185 188 112 118 73 70 Retail - industrial 216 211 107 111 109 100 Wholesale 46 47 12 15 34 32 Bulk power and other 36 34 14 6 22 28 Total Electric Utility 768 773 388 400 380 373 Gas Utility: Retail - residential 167 158 93 85 74 73 Retail - commercial 88 82 44 40 44 42 Retail - industrial 7 8 4 5 3 3 Transportation/other 14 14 9 9 5 5 Total Gas Utility 276 262 150 139 126 123 Other Utility: Steam 10 9 10 9 — — Other utility 1 2 1 2 — — Total Other Utility 11 11 11 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $1,077 $1,068 $549 $550 $506 $496

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2023
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. Alliant Energy IPL WPL 2023 2022 2023 2022 2023 2022 Overall income tax rate (1%) 4% (18%) (14%) 12% 19%
Summary Of Tax Credit Carryforwards	At March 31, 2023, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2043 $535 $12 $1 Federal tax credits 2027-2043 698 468 218
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. Alliant Energy IPL WPL 2023 2022 2023 2022 2023 2022 Overall income tax rate (1%) 4% (18%) (14%) 12% 19%
Summary Of Tax Credit Carryforwards	At March 31, 2023, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2043 $535 $12 $1 Federal tax credits 2027-2043 698 468 218
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. Alliant Energy IPL WPL 2023 2022 2023 2022 2023 2022 Overall income tax rate (1%) 4% (18%) (14%) 12% 19%
Summary Of Tax Credit Carryforwards	At March 31, 2023, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2043 $535 $12 $1 Federal tax credits 2027-2043 698 468 218

Benefit Plans (Tables)

Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2023
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 2023 2022 2023 2022 Service cost $1 $2 $1 $1 Interest cost 11 9 2 1 Expected return on plan assets (13) (17) (1) (1) Amortization of actuarial loss 7 8 — 1 $6 $2 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2023 2022 2023 2022 Service cost $1 $2 $— $— Interest cost 5 4 1 1 Expected return on plan assets (7) (8) (1) (1) Amortization of actuarial loss 3 3 — — $2 $1 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2023 2022 2023 2022 Service cost $— $1 $— $— Interest cost 5 4 1 1 Expected return on plan assets (5) (8) — — Amortization of actuarial loss 3 4 — — $3 $1 $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 2023 2022 2023 2022 2023 2022 Compensation expense $3 $4 $2 $2 $1 $2 Income tax benefits 1 1 — 1 — —
Schedule Of Equity-based Compensation Plans Activity	For the three months ended March 31, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing plans 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 100,055 $55.68 Performance restricted stock units 114,325 52.73 Restricted stock units 99,941 52.78
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 2023 2022 2023 2022 Service cost $1 $2 $1 $1 Interest cost 11 9 2 1 Expected return on plan assets (13) (17) (1) (1) Amortization of actuarial loss 7 8 — 1 $6 $2 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2023 2022 2023 2022 Service cost $1 $2 $— $— Interest cost 5 4 1 1 Expected return on plan assets (7) (8) (1) (1) Amortization of actuarial loss 3 3 — — $2 $1 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2023 2022 2023 2022 Service cost $— $1 $— $— Interest cost 5 4 1 1 Expected return on plan assets (5) (8) — — Amortization of actuarial loss 3 4 — — $3 $1 $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 2023 2022 2023 2022 2023 2022 Compensation expense $3 $4 $2 $2 $1 $2 Income tax benefits 1 1 — 1 — —
Schedule Of Equity-based Compensation Plans Activity	For the three months ended March 31, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing plans 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 100,055 $55.68 Performance restricted stock units 114,325 52.73 Restricted stock units 99,941 52.78
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 2023 2022 2023 2022 Service cost $1 $2 $1 $1 Interest cost 11 9 2 1 Expected return on plan assets (13) (17) (1) (1) Amortization of actuarial loss 7 8 — 1 $6 $2 $2 $2 Defined Benefit Pension Plans OPEB Plans IPL 2023 2022 2023 2022 Service cost $1 $2 $— $— Interest cost 5 4 1 1 Expected return on plan assets (7) (8) (1) (1) Amortization of actuarial loss 3 3 — — $2 $1 $— $— Defined Benefit Pension Plans OPEB Plans WPL 2023 2022 2023 2022 Service cost $— $1 $— $— Interest cost 5 4 1 1 Expected return on plan assets (5) (8) — — Amortization of actuarial loss 3 4 — — $3 $1 $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 2023 2022 2023 2022 2023 2022 Compensation expense $3 $4 $2 $2 $1 $2 Income tax benefits 1 1 — 1 — —
Schedule Of Equity-based Compensation Plans Activity	For the three months ended March 31, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing plans 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 100,055 $55.68 Performance restricted stock units 114,325 52.73 Restricted stock units 99,941 52.78

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2023
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of March 31, 2023, 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): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 922 2023-2025 3,276 2023 209,102 2023-2032 662 2023 IPL 391 2023-2025 1,338 2023 101,863 2023-2030 325 2023 WPL 531 2023 1,938 2023 107,239 2023-2032 337 2023
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 $28 $111 $17 $69 $11 $42 Non-current derivative assets 94 126 52 69 42 57 Current derivative liabilities 65 59 26 40 39 19 Non-current derivative liabilities 30 20 8 6 22 14
Balance Sheet Offsetting	However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions): Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2023 Derivative assets $122 $89 $69 $51 $53 $38 Derivative liabilities 95 62 34 16 61 46 December 31, 2022 Derivative assets 237 193 138 108 99 85 Derivative liabilities 79 35 46 16 33 19
IPL [Member]
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of March 31, 2023, 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): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 922 2023-2025 3,276 2023 209,102 2023-2032 662 2023 IPL 391 2023-2025 1,338 2023 101,863 2023-2030 325 2023 WPL 531 2023 1,938 2023 107,239 2023-2032 337 2023
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 $28 $111 $17 $69 $11 $42 Non-current derivative assets 94 126 52 69 42 57 Current derivative liabilities 65 59 26 40 39 19 Non-current derivative liabilities 30 20 8 6 22 14
Balance Sheet Offsetting	However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions): Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2023 Derivative assets $122 $89 $69 $51 $53 $38 Derivative liabilities 95 62 34 16 61 46 December 31, 2022 Derivative assets 237 193 138 108 99 85 Derivative liabilities 79 35 46 16 33 19
WPL [Member]
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of March 31, 2023, 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): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 922 2023-2025 3,276 2023 209,102 2023-2032 662 2023 IPL 391 2023-2025 1,338 2023 101,863 2023-2030 325 2023 WPL 531 2023 1,938 2023 107,239 2023-2032 337 2023
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 $28 $111 $17 $69 $11 $42 Non-current derivative assets 94 126 52 69 42 57 Current derivative liabilities 65 59 26 40 39 19 Non-current derivative liabilities 30 20 8 6 22 14
Balance Sheet Offsetting	However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions): Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2023 Derivative assets $122 $89 $69 $51 $53 $38 Derivative liabilities 95 62 34 16 61 46 December 31, 2022 Derivative assets 237 193 138 108 99 85 Derivative liabilities 79 35 46 16 33 19

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 December 31, 2022 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 $148 $148 $— $— $148 $10 $10 $— $— $10 Commodity derivatives 122 — 116 6 122 237 — 206 31 237 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 95 — 84 11 95 79 — 67 12 79 Interest rate derivatives 1 — 1 — 1 — — — — — Long-term debt (incl. current maturities) 8,940 — 8,461 1 8,462 8,076 — 7,338 1 7,339 IPL March 31, 2023 December 31, 2022 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 $30 $30 $— $— $30 $10 $10 $— $— $10 Commodity derivatives 69 — 63 6 69 138 — 111 27 138 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 34 — 28 6 34 46 — 35 11 46 Long-term debt 3,647 — 3,335 — 3,335 3,646 — 3,228 — 3,228 WPL March 31, 2023 December 31, 2022 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 $83 $83 $— $— $83 $— $— $— $— $— Commodity derivatives 53 — 53 — 53 99 — 95 4 99 Liabilities: Commodity derivatives 61 — 56 5 61 33 — 32 1 33 Long-term debt 3,067 — 2,939 — 2,939 2,770 — 2,542 — 2,542
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 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (4) (6) — — Settlements (a) (20) (13) (32) 13 Ending balance, March 31 ($5) $10 $153 $227 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) ($5) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (4) — — Settlements (a) (17) (7) (32) 13 Ending balance, March 31 $— $7 $153 $227 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 $1 ($4) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2023 2022 Beginning balance, January 1 $3 $11 Total net losses included in changes in net assets (realized/unrealized) (5) (2) Settlements (3) (6) Ending balance, March 31 ($5) $3 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) ($1) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2023 ($10) $5 ($4) $4 ($6) $1 December 31, 2022 (10) 29 (9) 25 (1) 4
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, 2023 December 31, 2022 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 $148 $148 $— $— $148 $10 $10 $— $— $10 Commodity derivatives 122 — 116 6 122 237 — 206 31 237 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 95 — 84 11 95 79 — 67 12 79 Interest rate derivatives 1 — 1 — 1 — — — — — Long-term debt (incl. current maturities) 8,940 — 8,461 1 8,462 8,076 — 7,338 1 7,339 IPL March 31, 2023 December 31, 2022 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 $30 $30 $— $— $30 $10 $10 $— $— $10 Commodity derivatives 69 — 63 6 69 138 — 111 27 138 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 34 — 28 6 34 46 — 35 11 46 Long-term debt 3,647 — 3,335 — 3,335 3,646 — 3,228 — 3,228 WPL March 31, 2023 December 31, 2022 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 $83 $83 $— $— $83 $— $— $— $— $— Commodity derivatives 53 — 53 — 53 99 — 95 4 99 Liabilities: Commodity derivatives 61 — 56 5 61 33 — 32 1 33 Long-term debt 3,067 — 2,939 — 2,939 2,770 — 2,542 — 2,542
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 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (4) (6) — — Settlements (a) (20) (13) (32) 13 Ending balance, March 31 ($5) $10 $153 $227 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) ($5) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (4) — — Settlements (a) (17) (7) (32) 13 Ending balance, March 31 $— $7 $153 $227 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 $1 ($4) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2023 2022 Beginning balance, January 1 $3 $11 Total net losses included in changes in net assets (realized/unrealized) (5) (2) Settlements (3) (6) Ending balance, March 31 ($5) $3 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) ($1) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2023 ($10) $5 ($4) $4 ($6) $1 December 31, 2022 (10) 29 (9) 25 (1) 4
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, 2023 December 31, 2022 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 $148 $148 $— $— $148 $10 $10 $— $— $10 Commodity derivatives 122 — 116 6 122 237 — 206 31 237 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 95 — 84 11 95 79 — 67 12 79 Interest rate derivatives 1 — 1 — 1 — — — — — Long-term debt (incl. current maturities) 8,940 — 8,461 1 8,462 8,076 — 7,338 1 7,339 IPL March 31, 2023 December 31, 2022 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 $30 $30 $— $— $30 $10 $10 $— $— $10 Commodity derivatives 69 — 63 6 69 138 — 111 27 138 Deferred proceeds 153 — — 153 153 185 — — 185 185 Liabilities: Commodity derivatives 34 — 28 6 34 46 — 35 11 46 Long-term debt 3,647 — 3,335 — 3,335 3,646 — 3,228 — 3,228 WPL March 31, 2023 December 31, 2022 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 $83 $83 $— $— $83 $— $— $— $— $— Commodity derivatives 53 — 53 — 53 99 — 95 4 99 Liabilities: Commodity derivatives 61 — 56 5 61 33 — 32 1 33 Long-term debt 3,067 — 2,939 — 2,939 2,770 — 2,542 — 2,542
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 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (4) (6) — — Settlements (a) (20) (13) (32) 13 Ending balance, March 31 ($5) $10 $153 $227 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) ($5) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (4) — — Settlements (a) (17) (7) (32) 13 Ending balance, March 31 $— $7 $153 $227 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 $1 ($4) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2023 2022 Beginning balance, January 1 $3 $11 Total net losses included in changes in net assets (realized/unrealized) (5) (2) Settlements (3) (6) Ending balance, March 31 ($5) $3 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) ($1) (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2023 ($10) $5 ($4) $4 ($6) $1 December 31, 2022 (10) 29 (9) 25 (1) 4

Commitments And Contingencies (

Commitments And Contingencies (Tables)	3 Months Ended
	Mar. 31, 2023
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At March 31, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,280 $565 $715 Coal 175 89 86 Other (a) 113 53 26 $1,568 $707 $827 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At March 31, 2023, 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): Alliant Energy IPL WPL Range of estimated future costs $10 - $37 $6 - $12 $4 - $25 Current and non-current environmental liabilities $18 $8 $10
IPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At March 31, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,280 $565 $715 Coal 175 89 86 Other (a) 113 53 26 $1,568 $707 $827 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At March 31, 2023, 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): Alliant Energy IPL WPL Range of estimated future costs $10 - $37 $6 - $12 $4 - $25 Current and non-current environmental liabilities $18 $8 $10
WPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At March 31, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,280 $565 $715 Coal 175 89 86 Other (a) 113 53 26 $1,568 $707 $827 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At March 31, 2023, 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): Alliant Energy IPL WPL Range of estimated future costs $10 - $37 $6 - $12 $4 - $25 Current and non-current environmental liabilities $18 $8 $10

Segments Of Business (Tables)

Segments Of Business (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 Revenues $768 $276 $11 $1,055 $22 $1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 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 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $388 $150 $11 $549 Operating income 66 27 3 96 Net income 72 Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income 87 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $380 $126 $— $506 Operating income 97 23 1 121 Net income 88 Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92
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, 2023 Revenues $768 $276 $11 $1,055 $22 $1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 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 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $388 $150 $11 $549 Operating income 66 27 3 96 Net income 72 Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income 87 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $380 $126 $— $506 Operating income 97 23 1 121 Net income 88 Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92
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, 2023 Revenues $768 $276 $11 $1,055 $22 $1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 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 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $388 $150 $11 $549 Operating income 66 27 3 96 Net income 72 Three Months Ended March 31, 2022 Revenues $400 $139 $11 $550 Operating income 75 32 3 110 Net income 87 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2023 Revenues $380 $126 $— $506 Operating income 97 23 1 121 Net income 88 Three Months Ended March 31, 2022 Revenues $373 $123 $— $496 Operating income 106 25 — 131 Net income 92

Related Parties (Tables)

Related Parties (Tables)	3 Months Ended
	Mar. 31, 2023
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 2023 2022 2023 2022 Corporate Services billings $40 $40 $36 $36 Sales credited 7 — 13 18 Purchases billed 93 94 15 22
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2023 December 31, 2022 March 31, 2023 December 31, 2022 Net payables to Corporate Services $110 $103 $65 $56
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three months ended March 31 were as follows (in millions): 2023 2022 ATC billings to WPL $34 $34 WPL billings to ATC 6 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 2023 2022 2023 2022 Corporate Services billings $40 $40 $36 $36 Sales credited 7 — 13 18 Purchases billed 93 94 15 22
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2023 December 31, 2022 March 31, 2023 December 31, 2022 Net payables to Corporate Services $110 $103 $65 $56
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 2023 2022 2023 2022 Corporate Services billings $40 $40 $36 $36 Sales credited 7 — 13 18 Purchases billed 93 94 15 22
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2023 December 31, 2022 March 31, 2023 December 31, 2022 Net payables to Corporate Services $110 $103 $65 $56
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three months ended March 31 were as follows (in millions): 2023 2022 ATC billings to WPL $34 $34 WPL billings to ATC 6 3

Summary Of Significant Accoun_3

Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 148	$ 10
Money market fund investments interest rate, percentage	5%
IPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 30	10
Money market fund investments interest rate, percentage	5%
WPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 83	$ 0
Money market fund investments interest rate, percentage	5%

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory assets	$ 2,080	$ 2,046
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	942	929
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	385	392
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	156	151
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	152	160
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	101	84
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	67	70
IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	60	66
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	48
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	169	146
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,383	1,386
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	857	848
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	193	197
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	115	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	4	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	37	48
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	51	53
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	60	66
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	63
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	697	660
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	85	81
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	192	195
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	41	41
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	148	159
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	64	36
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	16	17
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	48
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 103	$ 83

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,231	$ 1,324
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	575	579
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	403	398
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	117	210
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	26	20
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	24	32
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	22	40
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	64	45
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	697	754
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	302	303
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	261	259
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	64	115
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	19	10
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	8	38
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	43	29
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	534	570
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	273	276
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	142	139
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	53	95
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	7	10
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	24	32
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	14	2
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 21	$ 16

Property, Plant and Equipment (

Property, Plant and Equipment (Narrative) (Details)	Mar. 31, 2023
WPL [Member] | West Riverside Energy Center [Member]
Property, Plant and Equipment [Line Items]
Ownership interest, percent	87.60%

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Receivables [Line Items]
Gross write-offs for accounts receivable, originated in 2022	$ 5
IPL [Member]
Receivables [Line Items]
Gross write-offs for accounts receivable, originated in 2022	3
WPL [Member]
Receivables [Line Items]
Gross write-offs for accounts receivable, originated in 2022	2
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Available capacity	21
Receivables Sold [Member] | IPL [Member] | Financial Asset, Past Due [Member]
Receivables [Line Items]
Outstanding receivables past due	$ 26

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Maximum [Member]
Receivables [Line Items]
Maximum outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 89	$ 36
Average [Member]
Receivables [Line Items]
Average outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 58	$ 4

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Receivables [Line Items]
Fair value of deferred proceeds	$ 153	$ 185
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	153	185
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	161	145
Unbilled utility revenues	94	132
Receivables sold to third party	255	277
Less: cash proceeds	89	80
Deferred proceeds	166	197
Less: allowance for expected credit losses	13	12
Fair value of deferred proceeds	$ 153	$ 185

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Receivables [Line Items]
Collections	$ 591	$ 561
Write-offs, net of recoveries	$ 2	$ 2

Investments (Unconsolidated Equ

Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (17)	$ (15)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(13)	(11)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(4)	(4)
Total [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (17)	$ (15)

Common Equity (Common Share Act

Common Equity (Common Share Activity) (Details)	3 Months Ended
	Mar. 31, 2023 shares
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1, 2023 (in shares)	251,134,966
Shareowner Direct Plan (in shares)	118,488
Equity-based compensation plans (in shares)	134,334
Shares outstanding, March 31, 2023 (in shares)	251,387,788

Common Equity (Changes in Share

Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 6,276
Beginning balance	6,276	$ 5,990
Net income attributable to common shareowners	163	192
Net income	163	192
Common stock dividends	(113)	(107)
Shareowner Direct Plan issuances	6	7
Equity-based compensation plans and other	(3)	(5)
Other comprehensive loss, net of tax	(1)
Ending balance	6,328
Ending balance	$ 6,328	$ 6,077
Common stock dividends (in dollars per share)	$ 0.4525	$ 0.4275
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 3	$ 3
Ending balance	3	3
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,777	2,749
Shareowner Direct Plan issuances	6	7
Equity-based compensation plans and other	(3)	(6)
Ending balance	2,780	2,750
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,509	3,250
Net income attributable to common shareowners	163	192
Common stock dividends	(113)	(107)
Equity-based compensation plans and other		1
Ending balance	3,559	3,336
Accumulated Other Comprehensive Loss [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	0
Other comprehensive loss, net of tax	(1)
Ending balance	(1)	0
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(13)	(12)
Ending balance	(13)	(12)
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,808
Beginning balance	3,808	3,769
Net income	72	87
Common stock dividends	(70)	(81)
Ending balance	3,810
Ending balance	3,810	3,775
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	2,807
Ending balance	2,807	2,807
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	968	929
Net income	72	87
Common stock dividends	(70)	(81)
Ending balance	970	935
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,491
Beginning balance	3,491	2,823
Net income	88	92
Common stock dividends	(46)	(44)
Capital contributions from parent	180	180
Ending balance	3,713
Ending balance	3,713	3,051
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	2,233	1,704
Capital contributions from parent	180	180
Ending balance	2,413	1,884
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,192	1,053
Net income	88	92
Common stock dividends	(46)	(44)
Ending balance	$ 1,234	$ 1,101

Debt (Narrative) (Details)

Debt (Narrative) (Details)	3 Months Ended
	Mar. 31, 2023 USD ($) Integer $ / shares shares	Dec. 31, 2022 USD ($)
Debt [Line Items]
Line of credit facility, current borrowing capacity	$ 1,000,000,000
Long-term debt, fair value	8,462,000,000	$ 7,339,000,000
Parent Company [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	450,000,000
IPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	250,000,000
Long-term debt, fair value	3,335,000,000	3,228,000,000
WPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	300,000,000
Long-term debt, fair value	2,939,000,000	$ 2,542,000,000
Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024 [Member] | Alliant Energy Finance LLC [Member]
Debt [Line Items]
Long-term debt	50,000,000
Debentures [Member] | 4.95% debenture, due 2033 [Member] | WPL [Member]
Debt [Line Items]
Long-term debt	$ 300,000,000
Interest rate, percent	4.95%
Convertible Senior Notes [Member]
Debt [Line Items]
Trading days | Integer	20
Trading days consecutive | Integer	30
Convertible Senior Notes [Member] | 3.875% convertible senior notes, due 2026 [Member]
Debt [Line Items]
Long-term debt	$ 575,000,000
Interest rate, percent	3.875%
Trading days | Integer	5
Trading days consecutive | Integer	10
Principal amount of Notes conversion rate applied to	$ 1,000
Initial conversion ratio	15.5461
Initial conversion price | $ / shares	$ 64.32
Fundamental change repurchase conversion price, percent	100%
Long-term debt, carrying value	$ 565,000,000
Unamortized debt issuance costs	10,000,000
Long-term debt, fair value	$ 595,000,000
Shares included in diluted earnings per share (in shares) | shares	0
Convertible Senior Notes [Member] | 3.875% convertible senior notes, due 2026 [Member] | Maximum [Member]
Debt [Line Items]
Conversion price, percent	130%
Convertible Senior Notes [Member] | 3.875% convertible senior notes, due 2026 [Member] | Minimum [Member]
Debt [Line Items]
Conversion price, percent	98%

Debt (Credit Facilities) (Detai

Debt (Credit Facilities) (Details) $ in Millions	Mar. 31, 2023 USD ($)
Debt [Line Items]
Amount outstanding	$ 60
Weighted average interest rates	5.10%
Available credit facility capacity	$ 940
IPL [Member]
Debt [Line Items]
Amount outstanding	0
Available credit facility capacity	250
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 60
Weighted average interest rates	5.10%
Available credit facility capacity	$ 240

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 793	$ 577
Average amount outstanding (based on daily outstanding balances)	$ 574	$ 443
Weighted average interest rates	4.80%	0.30%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 349	$ 252
Average amount outstanding (based on daily outstanding balances)	$ 304	$ 205
Weighted average interest rates	4.80%	0.30%

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,077	$ 1,068
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	768	773
Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	285	293
Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	185	188
Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	216	211
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	46	47
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	36	34
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	276	262
Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	167	158
Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	88	82
Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7	8
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	14
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	11
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	9
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	2
Non-utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	22
Non-utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	22
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	549	550
IPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	388	400
IPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	143	150
IPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	112	118
IPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	107	111
IPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	15
IPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	6
IPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	150	139
IPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	93	85
IPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44	40
IPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	5
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	11
IPL [Member] | Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	9
IPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	2
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	506	496
WPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	380	373
WPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	142	143
WPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	73	70
WPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	109	100
WPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	32
WPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	28
WPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	126	123
WPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	74	73
WPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44	42
WPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	3
WPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	5
WPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
WPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Effective Tax Rate [Line Items]
Overall income tax rate	(1.00%)	4%
IPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	(18.00%)	(14.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	12%	19%

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Mar. 31, 2023 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 535
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	698
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	12
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	468
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 218

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) shares
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 18
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	$ 9
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 8
Omnibus Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Shares included in diluted earnings per share (in shares) | shares	170,209

Benefit Plans (Defined Benefit

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2
Interest cost	11	9
Expected return on plan assets	(13)	(17)
Amortization of actuarial loss	7	8
Total	6	2
OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	2	1
Expected return on plan assets	(1)	(1)
Amortization of actuarial loss	0	1
Total	2	2
IPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2
Interest cost	5	4
Expected return on plan assets	(7)	(8)
Amortization of actuarial loss	3	3
Total	2	1
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	0	1
Interest cost	5	4
Expected return on plan assets	(5)	(8)
Amortization of actuarial loss	3	4
Total	3	1
WPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of actuarial loss	0	0
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, 2023	Mar. 31, 2022
Compensation expense	$ 3	$ 4
Income tax benefits	1	1
IPL [Member]
Compensation expense	2	2
Income tax benefits	0	1
WPL [Member]
Compensation expense	1	2
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, 2023 $ / shares shares
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	100,055
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 55.68
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	114,325
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 52.73
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	99,941
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 52.78

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Derivative Instruments [Line Items]
Non-current interest rate swap liabilities	$ 540		$ 518
Accumulated other comprehensive loss, interest rate swap	(1)		$ 0
Interest expense, interest rate swap	94	$ 74
Alliant Energy Finance LLC [Member] | Interest Rate Swap [Member] | Term Loan Credit Agreement [Member]
Derivative Instruments [Line Items]
Interest rate swap	$ 300
Interest rate swap, fixed interest rate percentage	3.93%
Non-current interest rate swap liabilities	$ 1
Accumulated other comprehensive loss, interest rate swap	1
Interest expense, interest rate swap	$ 1

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] T in Thousands, MWh in Thousands, Dekatherms in Thousands	3 Months Ended
	Mar. 31, 2023 Dekatherms MWh T
Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	922
Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	391
Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	531
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	3,276
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	1,338
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	1,938
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	209,102
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	101,863
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	107,239
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	662
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	325
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	337

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 28	$ 111
Non-current derivative assets	94	126
Current derivative liabilities	65	59
Non-current derivative liabilities	30	20
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	17	69
Non-current derivative assets	52	69
Current derivative liabilities	26	40
Non-current derivative liabilities	8	6
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	11	42
Non-current derivative assets	42	57
Current derivative liabilities	39	19
Non-current derivative liabilities	$ 22	$ 14

Derivative Instruments (Balance

Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	$ 122	$ 237
Derivative assets, Net	89	193
Derivative liabilities, Gross (as reported)	95	79
Derivative liabilities, Net	62	35
IPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	69	138
Derivative assets, Net	51	108
Derivative liabilities, Gross (as reported)	34	46
Derivative liabilities, Net	16	16
WPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	53	99
Derivative assets, Net	38	85
Derivative liabilities, Gross (as reported)	61	33
Derivative liabilities, Net	$ 46	$ 19

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Assets:
Money market fund investments	$ 148	$ 10
Deferred proceeds	153	185
Liabilities:
Long-term debt (incl. current maturities)	8,462	7,339
IPL [Member]
Assets:
Money market fund investments	30	10
Deferred proceeds	153	185
Liabilities:
Long-term debt (incl. current maturities)	3,335	3,228
WPL [Member]
Assets:
Money market fund investments	83	0
Liabilities:
Long-term debt (incl. current maturities)	2,939	2,542
Commodity Contracts [Member]
Assets:
Derivatives	122	237
Liabilities:
Derivatives	95	79
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	69	138
Liabilities:
Derivatives	34	46
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	53	99
Liabilities:
Derivatives	61	33
Interest Rate Swap [Member]
Liabilities:
Derivatives	1	0
Level 1 [Member]
Assets:
Money market fund investments	148	10
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	30	10
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | WPL [Member]
Assets:
Money market fund investments	83	0
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 1 [Member] | Interest Rate Swap [Member]
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)	8,461	7,338
Level 2 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,335	3,228
Level 2 [Member] | WPL [Member]
Assets:
Money market fund investments	0	0
Liabilities:
Long-term debt (incl. current maturities)	2,939	2,542
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	116	206
Liabilities:
Derivatives	84	67
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	63	111
Liabilities:
Derivatives	28	35
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	53	95
Liabilities:
Derivatives	56	32
Level 2 [Member] | Interest Rate Swap [Member]
Liabilities:
Derivatives	1	0
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	153	185
Liabilities:
Long-term debt (incl. current maturities)	1	1
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	153	185
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | WPL [Member]
Assets:
Money market fund investments	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	6	31
Liabilities:
Derivatives	11	12
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	6	27
Liabilities:
Derivatives	6	11
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	0	4
Liabilities:
Derivatives	5	1
Level 3 [Member] | Interest Rate Swap [Member]
Liabilities:
Derivatives	0	0
Carrying Amount [Member]
Assets:
Money market fund investments	148	10
Deferred proceeds	153	185
Liabilities:
Long-term debt (incl. current maturities)	8,940	8,076
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	30	10
Deferred proceeds	153	185
Liabilities:
Long-term debt (incl. current maturities)	3,647	3,646
Carrying Amount [Member] | WPL [Member]
Assets:
Money market fund investments	83	0
Liabilities:
Long-term debt (incl. current maturities)	3,067	2,770
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	122	237
Liabilities:
Derivatives	95	79
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	69	138
Liabilities:
Derivatives	34	46
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	53	99
Liabilities:
Derivatives	61	33
Carrying Amount [Member] | Interest Rate Swap [Member]
Liabilities:
Derivatives	$ 1	$ 0

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 19	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	(4)	(6)
Settlements	(20)	(13)
Ending balance	(5)	10
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	(4)	(5)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	16	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	1	(4)
Settlements	(17)	(7)
Ending balance	0	7
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	1	(4)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	3	11
Total net gains (losses) included in changes in net assets (realized/unrealized)	(5)	(2)
Settlements	(3)	(6)
Ending balance	(5)	3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	(5)	(1)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Settlements	(32)	13
Ending balance	153	227
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	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	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Settlements	(32)	13
Ending balance	153	227
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	$ 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, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ (5)	$ 19	$ 10	$ 29
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative liabilities	(10)	(10)
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	5	29
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	0	16	7	18
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative liabilities	(4)	(9)
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	4	25
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	(5)	3	$ 3	$ 11
WPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative liabilities	(6)	(1)
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 1	$ 4

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2023	Jun. 30, 2021	Jun. 30, 2020
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,568
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	707
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	827
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	252
Capital Purchase Commitment [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	40
Capital Purchase Commitment [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	212
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	59
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	$ 17
Whiting Petroleum Affiliate [Member]
Commitments and Contingencies [Line Items]
Partnership share, percent	6%
Obligations, maximum	$ 58
Credit loss liability	$ 5
Federal Energy Regulatory Commission [Member]
Commitments and Contingencies [Line Items]
MISO base return on equity, percentage		10.02%	9.88%

Commitments And Contingencies_3

Commitments And Contingencies (Other Purchase Commitments) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,568
Individual commitments incurred	1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	707
Individual commitments incurred	1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	827
Individual commitments incurred	1
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,280
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	565
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	715
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	175
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	89
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	86
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	113
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	53
Other [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 26

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, 2023 USD ($)
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	$ 18
IPL [Member]
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	8
WPL [Member]
Commitments and Contingencies [Line Items]
Current and non-current environmental liabilities	10
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	6
Minimum [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	4
Maximum [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	37
Maximum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	12
Maximum [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	$ 25

Segments Of Business (Schedule

Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 1,077	$ 1,068
Operating income	222	248
Net income attributable to common shareowners	163	192
Net income	163	192
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	549	550
Operating income	96	110
Net income	72	87
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	506	496
Operating income	121	131
Net income	88	92
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	768	773
Operating income	163	181
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	388	400
Operating income	66	75
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	380	373
Operating income	97	106
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	276	262
Operating income	50	57
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	150	139
Operating income	27	32
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	126	123
Operating income	23	25
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	11	11
Operating income	4	3
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	11	11
Operating income	3	3
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Operating income	1	0
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	1,055	1,046
Operating income	217	241
Net income attributable to common shareowners	160	179
ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	22	22
Operating income	5	7
Net income attributable to common shareowners	$ 3	$ 13

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
WPL [Member] | WPL Owed ATC LLC [Member] | Related Party [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, 2023	Mar. 31, 2022
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	36
Sales Credited [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	7	0
Sales Credited [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	13	18
Purchases Billed [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	93	94
Purchases Billed [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 15	$ 22

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Subsidiary of Common Parent [Member] - Corporate Services [Member] - Related Party [Member] - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 110	$ 103
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 65	$ 56

Related Parties (Amounts Billed

Related Parties (Amounts Billed Between Parties) (Details) - ATC LLC [Member] - WPL [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
ATC Billings To WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 34	$ 34
WPL Billings To ATC [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 6	$ 3