Alliant Energy (LNT) 10-Q 3 Nov 23 2023 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	9 Months Ended
	Sep. 30, 2023 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 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	255,179,087
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
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		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Electric utility	$ 995	$ 1,039	$ 2,562	$ 2,624
Gas utility	47	62	400	418
Other utility	13	11	38	35
Non-utility	22	23	66	70
Total revenues	1,077	1,135	3,066	3,147
Operating expenses:
Electric production fuel and purchased power	231	274	553	633
Electric transmission service	154	157	438	428
Cost of gas sold	12	26	226	242
Other operation and maintenance	160	172	499	492
Depreciation and amortization	170	169	503	501
Taxes other than income taxes	28	28	87	82
Total operating expenses	755	826	2,306	2,378
Operating income	322	309	760	769
Other (income) and deductions:
Interest expense	99	83	289	235
Equity income from unconsolidated investments, net	(14)	(5)	(45)	(37)
Allowance for funds used during construction	(28)	(10)	(71)	(34)
Other	1	0	2	0
Total other (income) and deductions	58	68	175	164
Income before income taxes	264	241	585	605
Income tax expense (benefit)	5	14	3	26
Net income			582	579
Net income attributable to common shareowners	$ 259	$ 227	$ 582	$ 579
Weighted average number of common shares outstanding:
Basic (in shares)	253,500	251,000	252,100	250,800
Diluted (in shares)	253,800	251,300	252,400	251,100
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 1.02	$ 0.90	$ 2.31	$ 2.31
Diluted (in dollars per share)	$ 1.02	$ 0.90	$ 2.31	$ 2.31
IPL [Member]
Revenues:
Electric utility	$ 551	$ 596	$ 1,370	$ 1,438
Gas utility	31	33	224	224
Other utility	12	11	36	34
Total revenues	594	640	1,630	1,696
Operating expenses:
Electric production fuel and purchased power	99	140	213	290
Electric transmission service	115	115	316	303
Cost of gas sold	12	14	127	126
Other operation and maintenance	84	90	264	260
Depreciation and amortization	97	95	288	285
Taxes other than income taxes	14	15	43	43
Total operating expenses	421	469	1,251	1,307
Operating income	173	171	379	389
Other (income) and deductions:
Interest expense	38	37	113	111
Allowance for funds used during construction	(6)	(3)	(13)	(8)
Other	2	(1)	3	(2)
Total other (income) and deductions	34	33	103	101
Income before income taxes	139	138	276	288
Income tax expense (benefit)	(31)	(16)	(55)	(39)
Net income	170	154	331	327
WPL [Member]
Revenues:
Electric utility	444	443	1,192	1,186
Gas utility	16	29	176	194
Other utility	1	0	2	1
Total revenues	461	472	1,370	1,381
Operating expenses:
Electric production fuel and purchased power	132	134	341	343
Electric transmission service	39	42	122	125
Cost of gas sold	0	13	99	117
Other operation and maintenance	64	70	197	193
Depreciation and amortization	71	71	208	211
Taxes other than income taxes	13	11	40	35
Total operating expenses	319	341	1,007	1,024
Operating income	142	131	363	357
Other (income) and deductions:
Interest expense	38	31	110	86
Allowance for funds used during construction	(22)	(7)	(58)	(26)
Other	(2)	0	(3)	0
Total other (income) and deductions	14	24	49	60
Income before income taxes	128	107	314	297
Income tax expense (benefit)	21	16	47	50
Net income	$ 107	$ 91	$ 267	$ 247

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 206	$ 20
Accounts receivable, less allowance for expected credit losses	486	516
Production fuel, at weighted average cost	44	53
Gas stored underground, at weighted average cost	87	132
Materials and supplies, at weighted average cost	196	140
Regulatory assets	179	166
Other	174	223
Total current assets	1,372	1,250
Property, plant and equipment, net	16,633	16,247
Investments:
ATC Holdings	380	358
Other	214	201
Total investments	594	559
Other assets:
Regulatory assets	2,090	1,880
Deferred charges and other	215	227
Total other assets	2,305	2,107
Total assets	20,904	20,163
Current liabilities:
Current maturities of long-term debt	409	408
Commercial paper	451	642
Other short-term borrowings	50	0
Accounts payable	604	756
Regulatory liabilities	92	206
Other	329	351
Total current liabilities	1,935	2,363
Long-term debt, net (excluding current portion)	8,429	7,668
Other liabilities:
Deferred tax liabilities	1,913	1,943
Regulatory liabilities	1,095	1,118
Pension and other benefit obligations	262	277
Other	544	518
Total other liabilities	3,814	3,856
Commitments and contingencies (Note 13)
Common equity:
Common stock	3	3
Additional paid-in capital	2,982	2,777
Retained earnings	3,750	3,509
Accumulated other comprehensive income	4	0
Shares in deferred compensation trust - 393,781 and 402,134 shares at a weighted average cost of $34.13 and $32.63 per share	(13)	(13)
Total common equity	6,726	6,276
Total liabilities and equity	20,904	20,163
IPL [Member]
Current assets:
Cash and cash equivalents	188	15
Accounts receivable, less allowance for expected credit losses	258	259
Production fuel, at weighted average cost	22	23
Gas stored underground, at weighted average cost	40	60
Materials and supplies, at weighted average cost	111	83
Regulatory assets	86	85
Other	70	93
Total current assets	775	618
Property, plant and equipment, net	8,042	8,046
Other assets:
Regulatory assets	1,504	1,301
Deferred charges and other	106	110
Total other assets	1,610	1,411
Total assets	10,427	10,075
Current liabilities:
Accounts payable	255	239
Accounts payable to associated companies	59	28
Accrued taxes	68	52
Accrued interest	41	35
Regulatory liabilities	63	114
Other	84	113
Total current liabilities	570	581
Long-term debt, net (excluding current portion)	3,944	3,646
Other liabilities:
Deferred tax liabilities	987	1,047
Regulatory liabilities	592	640
Pension and other benefit obligations	59	62
Other	286	291
Total other liabilities	1,924	2,040
Commitments and contingencies (Note 13)
Common equity:
Common stock	33	33
Additional paid-in capital	2,867	2,807
Retained earnings	1,089	968
Total common equity	3,989	3,808
Total liabilities and equity	10,427	10,075
WPL [Member]
Current assets:
Cash and cash equivalents	16	5
Accounts receivable, less allowance for expected credit losses	214	244
Production fuel, at weighted average cost	21	29
Gas stored underground, at weighted average cost	47	73
Materials and supplies, at weighted average cost	82	54
Regulatory assets	93	81
Prepaid gross receipts tax	36	42
Other	50	60
Total current assets	559	588
Property, plant and equipment, net	8,085	7,722
Other assets:
Regulatory assets	586	579
Deferred charges and other	71	98
Total other assets	657	677
Total assets	9,301	8,987
Current liabilities:
Commercial paper	120	290
Accounts payable	281	456
Regulatory liabilities	29	92
Other	117	111
Total current liabilities	547	949
Long-term debt, net (excluding current portion)	3,069	2,770
Other liabilities:
Deferred tax liabilities	796	789
Regulatory liabilities	503	478
Pension and other benefit obligations	128	140
Other	393	370
Total other liabilities	1,820	1,777
Commitments and contingencies (Note 13)
Common equity:
Common stock	66	66
Additional paid-in capital	2,478	2,233
Retained earnings	1,321	1,192
Total common equity	3,865	3,491
Total liabilities and equity	$ 9,301	$ 8,987

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 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)	255,179,087	251,134,966
Shares in deferred compensation trust (in shares)	393,781	402,134
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 34.13	$ 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	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net income	$ 582	$ 579
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	503	501
Equity component of allowance for funds used during construction	(53)	(25)
Other	15	25
Other changes in assets and liabilities:
Accounts receivable	(279)	(425)
Materials and supplies	(56)	(13)
Derivative assets	102	(184)
Regulatory assets	40	(102)
Accounts payable	(91)	90
Derivative liabilities	(13)	89
Regulatory liabilities	(126)	89
Other	(2)	(139)
Net cash flows from operating activities	622	485
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(1,201)	(873)
Other construction and acquisition expenditures	(92)	(69)
Cash receipts on sold receivables	306	358
Proceeds from sales of partial ownership interest in West Riverside	120	0
Other	(85)	(15)
Net cash flows from (used for) investing activities	(952)	(599)
Cash flows from (used for) financing activities:
Common stock dividends	(341)	(322)
Proceeds from issuance of common stock, net	201	19
Proceeds from issuance of long-term debt	1,158	1,238
Payments to retire long-term debt	(404)	(379)
Net change in commercial paper and other short-term borrowings	(141)	(132)
Contributions from noncontrolling interest	0	29
Distributions to noncontrolling interest	0	(29)
Other	42	(3)
Net cash flows from (used for) financing activities	515	421
Net increase (decrease) in cash, cash equivalents and restricted cash	185	307
Cash, cash equivalents and restricted cash at beginning of period	24	40
Cash, cash equivalents and restricted cash at end of period	209	347
Supplemental cash flows information:
Interest	(280)	(220)
Income taxes, net	(6)	(7)
Significant non-cash investing and financing activities:
Accrued capital expenditures	287	403
Beneficial interest obtained in exchange for securitized accounts receivable	236	248
IPL [Member]
Cash flows from operating activities:
Net income	331	327
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	288	285
Deferred tax benefit and tax credits	(17)	(24)
Other	(6)	(8)
Other changes in assets and liabilities:
Accounts receivable	(306)	(397)
Derivative assets	53	(118)
Regulatory assets	55	18
Accounts payable	(45)	71
Derivative liabilities	(25)	62
Regulatory liabilities	(90)	61
Deferred income taxes	(44)	(30)
Other	(3)	(81)
Net cash flows from operating activities	191	166
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(427)	(269)
Cash receipts on sold receivables	306	358
Other	(56)	(5)
Net cash flows from (used for) investing activities	(177)	84
Cash flows from (used for) financing activities:
Common stock dividends	(210)	(240)
Capital contributions from parent	60	0
Proceeds from issuance of long-term debt	296	0
Other	13	1
Net cash flows from (used for) financing activities	159	(239)
Net increase (decrease) in cash, cash equivalents and restricted cash	173	11
Cash, cash equivalents and restricted cash at beginning of period	15	34
Cash, cash equivalents and restricted cash at end of period	188	45
Supplemental cash flows information:
Interest	(107)	(111)
Income taxes, net	36	33
Significant non-cash investing and financing activities:
Accrued capital expenditures	108	43
Beneficial interest obtained in exchange for securitized accounts receivable	236	248
WPL [Member]
Cash flows from operating activities:
Net income	267	247
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	208	211
Equity component of allowance for funds used during construction	(43)	(19)
Other	5	23
Other changes in assets and liabilities:
Derivative assets	55	(66)
Regulatory assets	(16)	(120)
Accounts payable	(55)	5
Regulatory liabilities	(37)	28
Other	53	(30)
Net cash flows from operating activities	437	279
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(774)	(604)
Proceeds from sales of partial ownership interest in West Riverside	120	0
Other	(26)	(8)
Net cash flows from (used for) investing activities	(680)	(612)
Cash flows from (used for) financing activities:
Common stock dividends	(138)	(133)
Capital contributions from parent	245	420
Proceeds from issuance of long-term debt	297	588
Net change in commercial paper and other short-term borrowings	(170)	(236)
Contributions from noncontrolling interest	0	29
Distributions to noncontrolling interest	0	(29)
Other	20	(9)
Net cash flows from (used for) financing activities	254	630
Net increase (decrease) in cash, cash equivalents and restricted cash	11	297
Cash, cash equivalents and restricted cash at beginning of period	5	2
Cash, cash equivalents and restricted cash at end of period	16	299
Supplemental cash flows information:
Interest	(106)	(78)
Income taxes, net	(63)	(51)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 172	$ 355

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	9 Months Ended
	Sep. 30, 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 nine months ended September 30, 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $189 million, $180 million and $9 million of money market fund investments, respectively, with weighted average 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 nine months ended September 30, 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $189 million, $180 million and $9 million of money market fund investments, respectively, with weighted average 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 nine months ended September 30, 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $189 million, $180 million and $9 million of money market fund investments, respectively, with weighted average interest rates of 5%.

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 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 September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $919 $929 $825 $848 $94 $81 Pension and OPEB costs 371 392 187 197 184 195 Assets retired early 282 70 267 53 15 17 Asset retirement obligations (AROs) 199 151 155 110 44 41 Commodity cost recovery 138 160 11 1 127 159 Derivatives 72 84 27 48 45 36 IPL’s Duane Arnold Energy Center PPA amendment 48 66 48 66 — — WPL’s Western Wisconsin gas distribution expansion investments 46 48 — — 46 48 Other 194 146 70 63 124 83 $2,269 $2,046 $1,590 $1,386 $679 $660 Tax-related - Refer to Note 9 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in the third quarter of 2023. Assets retired early and Asset retirement obligations - In May 2023, IPL retired the coal-fired Lansing Generating Station and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset (assets retired early) on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of September 30, 2023 was $221 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. In September 2023, the Federal Energy Regulatory Commission approved continued recovery of the remaining net book value of Lansing from IPL’s wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request for continued recovery of the remaining net book value of Lansing through 2037. In addition, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset (AROs) on Alliant Energy’s and IPL’s balance sheets. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2023, which resulted 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 September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $569 $579 $301 $303 $268 $276 Cost of removal obligations 397 398 249 259 148 139 Derivatives 91 210 52 115 39 95 Commodity cost recovery 41 40 11 38 30 2 WPL’s West Riverside liquidated damages 9 32 — — 9 32 Electric transmission cost recovery 6 20 6 10 — 10 Other 74 45 36 29 38 16 $1,187 $1,324 $655 $754 $532 $570 WPL’s West Riverside liquidated damages - Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, which resulted in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements for the three and nine months ended September 30, 2023.
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 September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $919 $929 $825 $848 $94 $81 Pension and OPEB costs 371 392 187 197 184 195 Assets retired early 282 70 267 53 15 17 Asset retirement obligations (AROs) 199 151 155 110 44 41 Commodity cost recovery 138 160 11 1 127 159 Derivatives 72 84 27 48 45 36 IPL’s Duane Arnold Energy Center PPA amendment 48 66 48 66 — — WPL’s Western Wisconsin gas distribution expansion investments 46 48 — — 46 48 Other 194 146 70 63 124 83 $2,269 $2,046 $1,590 $1,386 $679 $660 Tax-related - Refer to Note 9 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in the third quarter of 2023. Assets retired early and Asset retirement obligations - In May 2023, IPL retired the coal-fired Lansing Generating Station and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset (assets retired early) on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of September 30, 2023 was $221 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. In September 2023, the Federal Energy Regulatory Commission approved continued recovery of the remaining net book value of Lansing from IPL’s wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request for continued recovery of the remaining net book value of Lansing through 2037. In addition, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset (AROs) on Alliant Energy’s and IPL’s balance sheets. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2023, which resulted 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 September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $569 $579 $301 $303 $268 $276 Cost of removal obligations 397 398 249 259 148 139 Derivatives 91 210 52 115 39 95 Commodity cost recovery 41 40 11 38 30 2 WPL’s West Riverside liquidated damages 9 32 — — 9 32 Electric transmission cost recovery 6 20 6 10 — 10 Other 74 45 36 29 38 16 $1,187 $1,324 $655 $754 $532 $570 WPL’s West Riverside liquidated damages - Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, which resulted in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements for the three and nine months ended September 30, 2023.
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 September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $919 $929 $825 $848 $94 $81 Pension and OPEB costs 371 392 187 197 184 195 Assets retired early 282 70 267 53 15 17 Asset retirement obligations (AROs) 199 151 155 110 44 41 Commodity cost recovery 138 160 11 1 127 159 Derivatives 72 84 27 48 45 36 IPL’s Duane Arnold Energy Center PPA amendment 48 66 48 66 — — WPL’s Western Wisconsin gas distribution expansion investments 46 48 — — 46 48 Other 194 146 70 63 124 83 $2,269 $2,046 $1,590 $1,386 $679 $660 Tax-related - Refer to Note 9 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in the third quarter of 2023. Assets retired early and Asset retirement obligations - In May 2023, IPL retired the coal-fired Lansing Generating Station and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset (assets retired early) on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of September 30, 2023 was $221 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. In September 2023, the Federal Energy Regulatory Commission approved continued recovery of the remaining net book value of Lansing from IPL’s wholesale customers. IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request for continued recovery of the remaining net book value of Lansing through 2037. In addition, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset (AROs) on Alliant Energy’s and IPL’s balance sheets. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the nine months ended September 30, 2023, which resulted 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 September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $569 $579 $301 $303 $268 $276 Cost of removal obligations 397 398 249 259 148 139 Derivatives 91 210 52 115 39 95 Commodity cost recovery 41 40 11 38 30 2 WPL’s West Riverside liquidated damages 9 32 — — 9 32 Electric transmission cost recovery 6 20 6 10 — 10 Other 74 45 36 29 38 16 $1,187 $1,324 $655 $754 $532 $570 WPL’s West Riverside liquidated damages - Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, which resulted in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements for the three and nine months ended September 30, 2023.

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2023
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENTIn March 2023 and June 2023, Madison Gas and Electric Company and WEC Energy Group, Inc., respectively, acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interest in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements for the nine months ended September 30, 2023. As a result of these transactions, WPL’s undivided current ownership interest in West Riverside is 73.8%.
IPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENTIn March 2023 and June 2023, Madison Gas and Electric Company and WEC Energy Group, Inc., respectively, acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interest in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements for the nine months ended September 30, 2023. As a result of these transactions, WPL’s undivided current ownership interest in West Riverside is 73.8%.
WPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENTIn March 2023 and June 2023, Madison Gas and Electric Company and WEC Energy Group, Inc., respectively, acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interest in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements for the nine months ended September 30, 2023. As a result of these transactions, WPL’s undivided current ownership interest in West Riverside is 73.8%.

Receivables

Receivables	9 Months Ended
	Sep. 30, 2023
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three and nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable were as follows (in millions): Originated in 2022 Originated in 2023 Three Months Nine Months Three Months Nine Months Alliant Energy $3 $11 $6 $8 IPL 2 7 4 5 WPL 1 4 2 3 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 limit on cash proceeds fluctuates between $5 million and $110 million, which IPL may change periodically throughout the year. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of September 30, 2023, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $94 $36 $110 $66 Average outstanding aggregate cash proceeds 46 3 68 8 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): September 30, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 88 132 Other receivables 1 — Receivables sold to third party 250 277 Less: cash proceeds 1 80 Deferred proceeds 249 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $236 $185 As of September 30, 2023, outstanding receivables past due under the Receivables Agreement were $18 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Collections $616 $670 $1,720 $1,731 Write-offs, net of recoveries 5 3 9 6 Effective October 2023, the limit on cash proceeds under the Receivables Agreement is $5 million.
IPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three and nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable were as follows (in millions): Originated in 2022 Originated in 2023 Three Months Nine Months Three Months Nine Months Alliant Energy $3 $11 $6 $8 IPL 2 7 4 5 WPL 1 4 2 3 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 limit on cash proceeds fluctuates between $5 million and $110 million, which IPL may change periodically throughout the year. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of September 30, 2023, IPL had $109 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $94 $36 $110 $66 Average outstanding aggregate cash proceeds 46 3 68 8 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): September 30, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 88 132 Other receivables 1 — Receivables sold to third party 250 277 Less: cash proceeds 1 80 Deferred proceeds 249 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $236 $185 As of September 30, 2023, outstanding receivables past due under the Receivables Agreement were $18 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Collections $616 $670 $1,720 $1,731 Write-offs, net of recoveries 5 3 9 6 Effective October 2023, the limit on cash proceeds under the Receivables Agreement is $5 million.
WPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three and nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable were as follows (in millions): Originated in 2022 Originated in 2023 Three Months Nine Months Three Months Nine Months Alliant Energy $3 $11 $6 $8 IPL 2 7 4 5 WPL 1 4 2 3

Investments

Investments	9 Months Ended
	Sep. 30, 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 and nine months ended September 30 was as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 ATC Holdings ($12) ($7) ($37) ($29) Other (2) 2 (8) (8) ($14) ($5) ($45) ($37)

Common Equity

Common Equity	9 Months Ended
	Sep. 30, 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 At-the-market offering program 3,569,937 Shareowner Direct Plan 339,850 Equity-based compensation plans 134,334 Shares outstanding, September 30, 2023 255,179,087 At-the-Market Offering Program - In December 2022, Alliant Energy filed a prospectus supplement under which it may sell up to $225 million of its common stock through an at-the-market offering program. As of September 30, 2023, Alliant Energy issued 3,569,937 shares of common stock through this program and received cash proceeds of $183 million, net of $2 million in commissions and fees. The proceeds from the issuances of common stock were used for general corporate purposes. Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Net income attributable to Alliant Energy common shareowners 259 259 Common stock dividends ($0.4525 per share) (115) (115) At-the-market offering program and Shareowner Direct Plan issuances 125 125 Equity-based compensation plans and other 3 1 4 Other comprehensive income, net of tax 1 1 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 Net income attributable to Alliant Energy common shareowners 227 227 Common stock dividends ($0.4275 per share) (106) (106) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 2 (1) 1 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 582 582 Common stock dividends ($1.3575 per share) (341) (341) At-the-market offering program and Shareowner Direct Plan issuances 201 201 Equity-based compensation plans and other 4 4 Other comprehensive income, net of tax 4 4 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 579 579 Common stock dividends ($1.2825 per share) (322) (322) Shareowner Direct Plan issuances 19 19 Equity-based compensation plans and other (1) 1 (1) (1) Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $33 $2,847 $989 $3,869 Net income 170 170 Common stock dividends (70) (70) Capital contributions from parent 20 20 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $33 $2,807 $942 $3,782 Net income 154 154 Common stock dividends (80) (80) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 331 331 Common stock dividends (210) (210) Capital contributions from parent 60 60 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 327 327 Common stock dividends (240) (240) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Net income 107 107 Common stock dividends (46) (46) Capital contributions from parent 65 65 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 Net income 91 91 Common stock dividends (44) (44) Capital contributions from parent 155 155 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 267 267 Common stock dividends (138) (138) Capital contributions from parent 245 245 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 247 247 Common stock dividends (133) (133) Capital contributions from parent 420 420 Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Other (1) (1) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356
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 At-the-market offering program 3,569,937 Shareowner Direct Plan 339,850 Equity-based compensation plans 134,334 Shares outstanding, September 30, 2023 255,179,087 At-the-Market Offering Program - In December 2022, Alliant Energy filed a prospectus supplement under which it may sell up to $225 million of its common stock through an at-the-market offering program. As of September 30, 2023, Alliant Energy issued 3,569,937 shares of common stock through this program and received cash proceeds of $183 million, net of $2 million in commissions and fees. The proceeds from the issuances of common stock were used for general corporate purposes. Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Net income attributable to Alliant Energy common shareowners 259 259 Common stock dividends ($0.4525 per share) (115) (115) At-the-market offering program and Shareowner Direct Plan issuances 125 125 Equity-based compensation plans and other 3 1 4 Other comprehensive income, net of tax 1 1 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 Net income attributable to Alliant Energy common shareowners 227 227 Common stock dividends ($0.4275 per share) (106) (106) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 2 (1) 1 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 582 582 Common stock dividends ($1.3575 per share) (341) (341) At-the-market offering program and Shareowner Direct Plan issuances 201 201 Equity-based compensation plans and other 4 4 Other comprehensive income, net of tax 4 4 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 579 579 Common stock dividends ($1.2825 per share) (322) (322) Shareowner Direct Plan issuances 19 19 Equity-based compensation plans and other (1) 1 (1) (1) Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $33 $2,847 $989 $3,869 Net income 170 170 Common stock dividends (70) (70) Capital contributions from parent 20 20 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $33 $2,807 $942 $3,782 Net income 154 154 Common stock dividends (80) (80) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 331 331 Common stock dividends (210) (210) Capital contributions from parent 60 60 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 327 327 Common stock dividends (240) (240) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Net income 107 107 Common stock dividends (46) (46) Capital contributions from parent 65 65 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 Net income 91 91 Common stock dividends (44) (44) Capital contributions from parent 155 155 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 267 267 Common stock dividends (138) (138) Capital contributions from parent 245 245 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 247 247 Common stock dividends (133) (133) Capital contributions from parent 420 420 Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Other (1) (1) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356
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 At-the-market offering program 3,569,937 Shareowner Direct Plan 339,850 Equity-based compensation plans 134,334 Shares outstanding, September 30, 2023 255,179,087 At-the-Market Offering Program - In December 2022, Alliant Energy filed a prospectus supplement under which it may sell up to $225 million of its common stock through an at-the-market offering program. As of September 30, 2023, Alliant Energy issued 3,569,937 shares of common stock through this program and received cash proceeds of $183 million, net of $2 million in commissions and fees. The proceeds from the issuances of common stock were used for general corporate purposes. Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Net income attributable to Alliant Energy common shareowners 259 259 Common stock dividends ($0.4525 per share) (115) (115) At-the-market offering program and Shareowner Direct Plan issuances 125 125 Equity-based compensation plans and other 3 1 4 Other comprehensive income, net of tax 1 1 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 Net income attributable to Alliant Energy common shareowners 227 227 Common stock dividends ($0.4275 per share) (106) (106) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 2 (1) 1 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 582 582 Common stock dividends ($1.3575 per share) (341) (341) At-the-market offering program and Shareowner Direct Plan issuances 201 201 Equity-based compensation plans and other 4 4 Other comprehensive income, net of tax 4 4 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 579 579 Common stock dividends ($1.2825 per share) (322) (322) Shareowner Direct Plan issuances 19 19 Equity-based compensation plans and other (1) 1 (1) (1) Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $33 $2,847 $989 $3,869 Net income 170 170 Common stock dividends (70) (70) Capital contributions from parent 20 20 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $33 $2,807 $942 $3,782 Net income 154 154 Common stock dividends (80) (80) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 331 331 Common stock dividends (210) (210) Capital contributions from parent 60 60 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 327 327 Common stock dividends (240) (240) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Net income 107 107 Common stock dividends (46) (46) Capital contributions from parent 65 65 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 Net income 91 91 Common stock dividends (44) (44) Capital contributions from parent 155 155 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 267 267 Common stock dividends (138) (138) Capital contributions from parent 245 245 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 247 247 Common stock dividends (133) (133) Capital contributions from parent 420 420 Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Other (1) (1) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356

Debt

Debt	9 Months Ended
	Sep. 30, 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): September 30, 2023 Alliant Energy IPL WPL Amount outstanding $451 $— $120 Weighted average interest rates 5.5% —% 5.4% Available credit facility capacity $549 $250 $180 Alliant Energy IPL WPL Three Months Ended September 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $474 $449 $7 $— $125 $251 Average amount outstanding (based on daily outstanding balances) $440 $353 $— $— $86 $110 Weighted average interest rates 5.5% 2.4% 5.5% —% 5.4% 2.0% Nine Months Ended September 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $367 $377 $2 $— $135 $160 Weighted average interest rates 5.1% 1.2% 5.3% —% 4.9% 0.9% 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 September 30, 2023. NOTE 7(b) Long-term Debt - In September 2023, IPL issued $300 million of 5.70% senior debentures due 2033. The net proceeds from IPL’s issuance were used to reduce cash amounts received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt, for general corporate purposes and/or were placed in money market fund investments. In June 2023, AEF retired its $400 million 3.75% senior notes. In March 2023, WPL issued $300 million of 4.95% debentures due 2033. WPL’s debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of its 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 initial conversion rate is 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 is 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. As of September 30, 2023, the conditions allowing holders of the Notes to convert their Notes were not met, and as a result, the Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet. As of September 30, 2023, the net carrying amount of the Notes was $567 million, with unamortized debt issuance costs of $8 million, and the estimated fair value (Level 2) of the Notes was $556 million. As of September 30, 2023, there were no shares of Alliant Energy’s common stock related to the potential conversion of the Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the Notes.
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): September 30, 2023 Alliant Energy IPL WPL Amount outstanding $451 $— $120 Weighted average interest rates 5.5% —% 5.4% Available credit facility capacity $549 $250 $180 Alliant Energy IPL WPL Three Months Ended September 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $474 $449 $7 $— $125 $251 Average amount outstanding (based on daily outstanding balances) $440 $353 $— $— $86 $110 Weighted average interest rates 5.5% 2.4% 5.5% —% 5.4% 2.0% Nine Months Ended September 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $367 $377 $2 $— $135 $160 Weighted average interest rates 5.1% 1.2% 5.3% —% 4.9% 0.9% 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 September 30, 2023. NOTE 7(b) Long-term Debt - In September 2023, IPL issued $300 million of 5.70% senior debentures due 2033. The net proceeds from IPL’s issuance were used to reduce cash amounts received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt, for general corporate purposes and/or were placed in money market fund investments. In June 2023, AEF retired its $400 million 3.75% senior notes. In March 2023, WPL issued $300 million of 4.95% debentures due 2033. WPL’s debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of its solar EGUs.
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): September 30, 2023 Alliant Energy IPL WPL Amount outstanding $451 $— $120 Weighted average interest rates 5.5% —% 5.4% Available credit facility capacity $549 $250 $180 Alliant Energy IPL WPL Three Months Ended September 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $474 $449 $7 $— $125 $251 Average amount outstanding (based on daily outstanding balances) $440 $353 $— $— $86 $110 Weighted average interest rates 5.5% 2.4% 5.5% —% 5.4% 2.0% Nine Months Ended September 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $367 $377 $2 $— $135 $160 Weighted average interest rates 5.1% 1.2% 5.3% —% 4.9% 0.9% 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 September 30, 2023. NOTE 7(b) Long-term Debt - In September 2023, IPL issued $300 million of 5.70% senior debentures due 2033. The net proceeds from IPL’s issuance were used to reduce cash amounts received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt, for general corporate purposes and/or were placed in money market fund investments. In June 2023, AEF retired its $400 million 3.75% senior notes. In March 2023, WPL issued $300 million of 4.95% debentures due 2033. WPL’s debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of its solar EGUs.

Revenues

Revenues	9 Months Ended
	Sep. 30, 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 September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $374 $376 $209 $222 $165 $154 Retail - commercial 241 243 158 165 83 78 Retail - industrial 280 289 153 172 127 117 Wholesale 59 68 21 19 38 49 Bulk power and other 41 63 10 18 31 45 Total Electric Utility 995 1,039 551 596 444 443 Gas Utility: Retail - residential 23 28 14 14 9 14 Retail - commercial 12 18 9 8 3 10 Retail - industrial 2 4 2 3 — 1 Transportation/other 10 12 6 8 4 4 Total Gas Utility 47 62 31 33 16 29 Other Utility: Steam 11 9 11 9 — — Other utility 2 2 1 2 1 — Total Other Utility 13 11 12 11 1 — Non-Utility and Other: Travero and other 22 23 — — — — Total Non-Utility and Other 22 23 — — — — Total revenues $1,077 $1,135 $594 $640 $461 $472 Alliant Energy IPL WPL Nine Months Ended September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $943 $956 $503 $529 $440 $427 Retail - commercial 627 628 399 411 228 217 Retail - industrial 740 743 389 418 351 325 Wholesale 154 168 47 49 107 119 Bulk power and other 98 129 32 31 66 98 Total Electric Utility 2,562 2,624 1,370 1,438 1,192 1,186 Gas Utility: Retail - residential 233 237 131 127 102 110 Retail - commercial 122 127 65 62 57 65 Retail - industrial 12 15 8 10 4 5 Transportation/other 33 39 20 25 13 14 Total Gas Utility 400 418 224 224 176 194 Other Utility: Steam 32 29 32 29 — — Other utility 6 6 4 5 2 1 Total Other Utility 38 35 36 34 2 1 Non-Utility and Other: Travero and other 66 70 — — — — Total Non-Utility and Other 66 70 — — — — Total revenues $3,066 $3,147 $1,630 $1,696 $1,370 $1,381
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 September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $374 $376 $209 $222 $165 $154 Retail - commercial 241 243 158 165 83 78 Retail - industrial 280 289 153 172 127 117 Wholesale 59 68 21 19 38 49 Bulk power and other 41 63 10 18 31 45 Total Electric Utility 995 1,039 551 596 444 443 Gas Utility: Retail - residential 23 28 14 14 9 14 Retail - commercial 12 18 9 8 3 10 Retail - industrial 2 4 2 3 — 1 Transportation/other 10 12 6 8 4 4 Total Gas Utility 47 62 31 33 16 29 Other Utility: Steam 11 9 11 9 — — Other utility 2 2 1 2 1 — Total Other Utility 13 11 12 11 1 — Non-Utility and Other: Travero and other 22 23 — — — — Total Non-Utility and Other 22 23 — — — — Total revenues $1,077 $1,135 $594 $640 $461 $472 Alliant Energy IPL WPL Nine Months Ended September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $943 $956 $503 $529 $440 $427 Retail - commercial 627 628 399 411 228 217 Retail - industrial 740 743 389 418 351 325 Wholesale 154 168 47 49 107 119 Bulk power and other 98 129 32 31 66 98 Total Electric Utility 2,562 2,624 1,370 1,438 1,192 1,186 Gas Utility: Retail - residential 233 237 131 127 102 110 Retail - commercial 122 127 65 62 57 65 Retail - industrial 12 15 8 10 4 5 Transportation/other 33 39 20 25 13 14 Total Gas Utility 400 418 224 224 176 194 Other Utility: Steam 32 29 32 29 — — Other utility 6 6 4 5 2 1 Total Other Utility 38 35 36 34 2 1 Non-Utility and Other: Travero and other 66 70 — — — — Total Non-Utility and Other 66 70 — — — — Total revenues $3,066 $3,147 $1,630 $1,696 $1,370 $1,381
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 September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $374 $376 $209 $222 $165 $154 Retail - commercial 241 243 158 165 83 78 Retail - industrial 280 289 153 172 127 117 Wholesale 59 68 21 19 38 49 Bulk power and other 41 63 10 18 31 45 Total Electric Utility 995 1,039 551 596 444 443 Gas Utility: Retail - residential 23 28 14 14 9 14 Retail - commercial 12 18 9 8 3 10 Retail - industrial 2 4 2 3 — 1 Transportation/other 10 12 6 8 4 4 Total Gas Utility 47 62 31 33 16 29 Other Utility: Steam 11 9 11 9 — — Other utility 2 2 1 2 1 — Total Other Utility 13 11 12 11 1 — Non-Utility and Other: Travero and other 22 23 — — — — Total Non-Utility and Other 22 23 — — — — Total revenues $1,077 $1,135 $594 $640 $461 $472 Alliant Energy IPL WPL Nine Months Ended September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $943 $956 $503 $529 $440 $427 Retail - commercial 627 628 399 411 228 217 Retail - industrial 740 743 389 418 351 325 Wholesale 154 168 47 49 107 119 Bulk power and other 98 129 32 31 66 98 Total Electric Utility 2,562 2,624 1,370 1,438 1,192 1,186 Gas Utility: Retail - residential 233 237 131 127 102 110 Retail - commercial 122 127 65 62 57 65 Retail - industrial 12 15 8 10 4 5 Transportation/other 33 39 20 25 13 14 Total Gas Utility 400 418 224 224 176 194 Other Utility: Steam 32 29 32 29 — — Other utility 6 6 4 5 2 1 Total Other Utility 38 35 36 34 2 1 Non-Utility and Other: Travero and other 66 70 — — — — Total Non-Utility and Other 66 70 — — — — Total revenues $3,066 $3,147 $1,630 $1,696 $1,370 $1,381

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2023
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates for the three and nine months ended September 30, 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 Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate 2% 6% 1% 4% (22%) (12%) (20%) (14%) 16% 15% 15% 17% Deferred Tax Assets and Liabilities - Carryforwards - At September 30, 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 $431 $6 $1 Federal tax credits 2031-2043 737 520 208 Iowa Tax Reform - Pursuant to Iowa tax reform enacted in 2022, in September 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 7.1%, effective January 1, 2024. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2024, which resulted in a $73 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in the third quarter of 2023. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2024, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in the third quarter of 2023. Based on the remeasurement of Alliant Energy parent company’s deferred tax assets in the third quarter of 2022 for the Iowa corporate income tax rate of 8.4% effective January 1, 2023, a charge of $8 million was recorded to income tax expense in Alliant Energy’s income statement in the third quarter of 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.
IPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates for the three and nine months ended September 30, 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 Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate 2% 6% 1% 4% (22%) (12%) (20%) (14%) 16% 15% 15% 17% Deferred Tax Assets and Liabilities - Carryforwards - At September 30, 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 $431 $6 $1 Federal tax credits 2031-2043 737 520 208 Iowa Tax Reform - Pursuant to Iowa tax reform enacted in 2022, in September 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 7.1%, effective January 1, 2024. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2024, which resulted in a $73 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in the third quarter of 2023. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2024, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in the third quarter of 2023. Based on the remeasurement of Alliant Energy parent company’s deferred tax assets in the third quarter of 2022 for the Iowa corporate income tax rate of 8.4% effective January 1, 2023, a charge of $8 million was recorded to income tax expense in Alliant Energy’s income statement in the third quarter of 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.
WPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates for the three and nine months ended September 30, 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 Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate 2% 6% 1% 4% (22%) (12%) (20%) (14%) 16% 15% 15% 17% Deferred Tax Assets and Liabilities - Carryforwards - At September 30, 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 $431 $6 $1 Federal tax credits 2031-2043 737 520 208 Iowa Tax Reform - Pursuant to Iowa tax reform enacted in 2022, in September 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 7.1%, effective January 1, 2024. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2024, which resulted in a $73 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in the third quarter of 2023. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2024, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in the third quarter of 2023. Based on the remeasurement of Alliant Energy parent company’s deferred tax assets in the third quarter of 2022 for the Iowa corporate income tax rate of 8.4% effective January 1, 2023, a charge of $8 million was recorded to income tax expense in Alliant Energy’s income statement in the third quarter of 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.

Benefit Plans

Benefit Plans	9 Months Ended
	Sep. 30, 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 and nine months ended September 30 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 Three Months Nine Months Three Months Nine Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $2 $3 $4 $7 $1 $— $2 $2 Interest cost 12 9 35 27 3 1 7 4 Expected return on plan assets (14) (18) (40) (52) (2) — (4) (3) Amortization of prior service credit (1) — (1) — — — — — Amortization of actuarial loss 7 8 21 24 — 1 1 2 $6 $2 $19 $6 $2 $2 $6 $5 Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $1 $2 $4 $— $— $— $1 Interest cost 6 4 16 12 1 1 3 2 Expected return on plan assets (6) (7) (19) (23) (1) (1) (3) (3) Amortization of actuarial loss 2 3 8 10 — — 1 — $2 $1 $7 $3 $— $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $— $1 $2 $1 $— $1 $— Interest cost 5 4 15 12 1 1 3 2 Expected return on plan assets (5) (7) (16) (23) (1) — (1) — Amortization of actuarial loss 3 4 10 12 — — — 1 $3 $1 $10 $3 $1 $1 $3 $3 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 and nine months ended September 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $4 $3 $10 $9 $2 $2 $5 $5 $2 $1 $4 $4 Income tax benefits 1 1 3 3 1 — 1 1 — — 1 1 As of September 30, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $11 million, $6 million and $5 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the nine months ended September 30, 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 108,513 $55.68 Performance restricted stock units 123,990 52.71 Restricted stock units 105,982 52.77 As of September 30, 2023, 274,960 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 and nine months ended September 30 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 Three Months Nine Months Three Months Nine Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $2 $3 $4 $7 $1 $— $2 $2 Interest cost 12 9 35 27 3 1 7 4 Expected return on plan assets (14) (18) (40) (52) (2) — (4) (3) Amortization of prior service credit (1) — (1) — — — — — Amortization of actuarial loss 7 8 21 24 — 1 1 2 $6 $2 $19 $6 $2 $2 $6 $5 Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $1 $2 $4 $— $— $— $1 Interest cost 6 4 16 12 1 1 3 2 Expected return on plan assets (6) (7) (19) (23) (1) (1) (3) (3) Amortization of actuarial loss 2 3 8 10 — — 1 — $2 $1 $7 $3 $— $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $— $1 $2 $1 $— $1 $— Interest cost 5 4 15 12 1 1 3 2 Expected return on plan assets (5) (7) (16) (23) (1) — (1) — Amortization of actuarial loss 3 4 10 12 — — — 1 $3 $1 $10 $3 $1 $1 $3 $3 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 and nine months ended September 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $4 $3 $10 $9 $2 $2 $5 $5 $2 $1 $4 $4 Income tax benefits 1 1 3 3 1 — 1 1 — — 1 1 As of September 30, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $11 million, $6 million and $5 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the nine months ended September 30, 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 108,513 $55.68 Performance restricted stock units 123,990 52.71 Restricted stock units 105,982 52.77 As of September 30, 2023, 274,960 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 and nine months ended September 30 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 Three Months Nine Months Three Months Nine Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $2 $3 $4 $7 $1 $— $2 $2 Interest cost 12 9 35 27 3 1 7 4 Expected return on plan assets (14) (18) (40) (52) (2) — (4) (3) Amortization of prior service credit (1) — (1) — — — — — Amortization of actuarial loss 7 8 21 24 — 1 1 2 $6 $2 $19 $6 $2 $2 $6 $5 Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $1 $2 $4 $— $— $— $1 Interest cost 6 4 16 12 1 1 3 2 Expected return on plan assets (6) (7) (19) (23) (1) (1) (3) (3) Amortization of actuarial loss 2 3 8 10 — — 1 — $2 $1 $7 $3 $— $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $— $1 $2 $1 $— $1 $— Interest cost 5 4 15 12 1 1 3 2 Expected return on plan assets (5) (7) (16) (23) (1) — (1) — Amortization of actuarial loss 3 4 10 12 — — — 1 $3 $1 $10 $3 $1 $1 $3 $3 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 and nine months ended September 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $4 $3 $10 $9 $2 $2 $5 $5 $2 $1 $4 $4 Income tax benefits 1 1 3 3 1 — 1 1 — — 1 1 As of September 30, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $11 million, $6 million and $5 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the nine months ended September 30, 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 108,513 $55.68 Performance restricted stock units 123,990 52.71 Restricted stock units 105,982 52.77 As of September 30, 2023, 274,960 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2023
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of September 30, 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 1,661 2023-2026 18,122 2023-2024 180,519 2023-2032 370 2023 IPL 746 2023-2026 8,078 2023-2024 85,457 2023-2030 217 2023 WPL 915 2023-2026 10,044 2023-2024 95,062 2023-2032 153 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 September 30, December 31, September 30, December 31, September 30, December 31, Current derivative assets $67 $111 $51 $69 $16 $42 Non-current derivative assets 62 126 34 69 28 57 Current derivative liabilities 32 59 15 40 17 19 Non-current derivative liabilities 34 20 6 6 28 14 During the nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s derivative assets decreased primarily due to settlements of natural gas, FTR and electricity contracts and lower natural gas prices, partially offset by new FTRs resulting from the annual FTR auction in the second quarter of 2023 operated by MISO. Alliant Energy’s and IPL’s derivative liabilities decreased primarily due to settlement 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 September 30, 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 September 30, 2023 Derivative assets $129 $108 $85 $73 $44 $35 Derivative liabilities 66 45 21 9 45 36 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 September 30, 2023, $6 million of non-current interest rate derivative assets was recorded in “Deferred charges and other” 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 September 30, 2023, accumulated other comprehensive income included $4 million of income related to the interest rate swap. For the three and nine months ended September 30, 2023, $1 million and $2 million, respectively, of reductions to interest expense were 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 September 30, 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 1,661 2023-2026 18,122 2023-2024 180,519 2023-2032 370 2023 IPL 746 2023-2026 8,078 2023-2024 85,457 2023-2030 217 2023 WPL 915 2023-2026 10,044 2023-2024 95,062 2023-2032 153 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 September 30, December 31, September 30, December 31, September 30, December 31, Current derivative assets $67 $111 $51 $69 $16 $42 Non-current derivative assets 62 126 34 69 28 57 Current derivative liabilities 32 59 15 40 17 19 Non-current derivative liabilities 34 20 6 6 28 14 During the nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s derivative assets decreased primarily due to settlements of natural gas, FTR and electricity contracts and lower natural gas prices, partially offset by new FTRs resulting from the annual FTR auction in the second quarter of 2023 operated by MISO. Alliant Energy’s and IPL’s derivative liabilities decreased primarily due to settlement 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 September 30, 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 September 30, 2023 Derivative assets $129 $108 $85 $73 $44 $35 Derivative liabilities 66 45 21 9 45 36 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 September 30, 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 1,661 2023-2026 18,122 2023-2024 180,519 2023-2032 370 2023 IPL 746 2023-2026 8,078 2023-2024 85,457 2023-2030 217 2023 WPL 915 2023-2026 10,044 2023-2024 95,062 2023-2032 153 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 September 30, December 31, September 30, December 31, September 30, December 31, Current derivative assets $67 $111 $51 $69 $16 $42 Non-current derivative assets 62 126 34 69 28 57 Current derivative liabilities 32 59 15 40 17 19 Non-current derivative liabilities 34 20 6 6 28 14 During the nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s derivative assets decreased primarily due to settlements of natural gas, FTR and electricity contracts and lower natural gas prices, partially offset by new FTRs resulting from the annual FTR auction in the second quarter of 2023 operated by MISO. Alliant Energy’s and IPL’s derivative liabilities decreased primarily due to settlement 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 September 30, 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 September 30, 2023 Derivative assets $129 $108 $85 $73 $44 $35 Derivative liabilities 66 45 21 9 45 36 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	9 Months Ended
	Sep. 30, 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 September 30, 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 $189 $189 $— $— $189 $10 $10 $— $— $10 Commodity derivatives 129 — 80 49 129 237 — 206 31 237 Interest rate derivatives 6 — 6 — 6 — — — — — Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 66 — 60 6 66 79 — 67 12 79 Long-term debt (incl. current maturities) 8,838 — 7,863 — 7,863 8,076 — 7,338 1 7,339 IPL September 30, 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 $180 $180 $— $— $180 $10 $10 $— $— $10 Commodity derivatives 85 — 45 40 85 138 — 111 27 138 Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 21 — 16 5 21 46 — 35 11 46 Long-term debt 3,944 — 3,422 — 3,422 3,646 — 3,228 — 3,228 WPL September 30, 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: Commodity derivatives $44 $— $35 $9 $44 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 45 — 44 1 45 33 — 32 1 33 Long-term debt 3,069 — 2,722 — 2,722 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 September 30 2023 2022 2023 2022 Beginning balance, July 1 $54 $72 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 17 (1) — — Sales (1) — — — Settlements (a) (27) (26) 61 4 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $17 ($1) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (17) — — Purchases 62 79 — — Sales (2) — — — Settlements (a) (42) (46) 51 34 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $6 ($17) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended September 30 2023 2022 2023 2022 Beginning balance, July 1 $41 $58 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 12 (6) — — Sales (1) — — — Settlements (a) (17) (19) 61 4 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $12 ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) — (13) — — Purchases 51 58 — — Sales (2) — — — Settlements (a) (30) (30) 51 34 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $— ($14) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended September 30 2023 2022 Beginning balance, July 1 $13 $14 Total net gains included in changes in net assets (realized/unrealized) 5 5 Settlements (10) (7) Ending balance, September 30 $8 $12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 $5 $5 WPL Commodity Contract Derivative Assets and (Liabilities), net Nine Months Ended September 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (4) Purchases 11 21 Settlements (12) (16) Ending balance, September 30 $8 $12 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 September 30 $6 ($3) (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 September 30, 2023 $3 $40 $4 $31 ($1) $9 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 September 30, 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 $189 $189 $— $— $189 $10 $10 $— $— $10 Commodity derivatives 129 — 80 49 129 237 — 206 31 237 Interest rate derivatives 6 — 6 — 6 — — — — — Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 66 — 60 6 66 79 — 67 12 79 Long-term debt (incl. current maturities) 8,838 — 7,863 — 7,863 8,076 — 7,338 1 7,339 IPL September 30, 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 $180 $180 $— $— $180 $10 $10 $— $— $10 Commodity derivatives 85 — 45 40 85 138 — 111 27 138 Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 21 — 16 5 21 46 — 35 11 46 Long-term debt 3,944 — 3,422 — 3,422 3,646 — 3,228 — 3,228 WPL September 30, 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: Commodity derivatives $44 $— $35 $9 $44 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 45 — 44 1 45 33 — 32 1 33 Long-term debt 3,069 — 2,722 — 2,722 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 September 30 2023 2022 2023 2022 Beginning balance, July 1 $54 $72 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 17 (1) — — Sales (1) — — — Settlements (a) (27) (26) 61 4 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $17 ($1) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (17) — — Purchases 62 79 — — Sales (2) — — — Settlements (a) (42) (46) 51 34 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $6 ($17) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended September 30 2023 2022 2023 2022 Beginning balance, July 1 $41 $58 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 12 (6) — — Sales (1) — — — Settlements (a) (17) (19) 61 4 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $12 ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) — (13) — — Purchases 51 58 — — Sales (2) — — — Settlements (a) (30) (30) 51 34 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $— ($14) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended September 30 2023 2022 Beginning balance, July 1 $13 $14 Total net gains included in changes in net assets (realized/unrealized) 5 5 Settlements (10) (7) Ending balance, September 30 $8 $12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 $5 $5 WPL Commodity Contract Derivative Assets and (Liabilities), net Nine Months Ended September 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (4) Purchases 11 21 Settlements (12) (16) Ending balance, September 30 $8 $12 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 September 30 $6 ($3) (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 September 30, 2023 $3 $40 $4 $31 ($1) $9 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 September 30, 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 $189 $189 $— $— $189 $10 $10 $— $— $10 Commodity derivatives 129 — 80 49 129 237 — 206 31 237 Interest rate derivatives 6 — 6 — 6 — — — — — Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 66 — 60 6 66 79 — 67 12 79 Long-term debt (incl. current maturities) 8,838 — 7,863 — 7,863 8,076 — 7,338 1 7,339 IPL September 30, 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 $180 $180 $— $— $180 $10 $10 $— $— $10 Commodity derivatives 85 — 45 40 85 138 — 111 27 138 Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 21 — 16 5 21 46 — 35 11 46 Long-term debt 3,944 — 3,422 — 3,422 3,646 — 3,228 — 3,228 WPL September 30, 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: Commodity derivatives $44 $— $35 $9 $44 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 45 — 44 1 45 33 — 32 1 33 Long-term debt 3,069 — 2,722 — 2,722 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 September 30 2023 2022 2023 2022 Beginning balance, July 1 $54 $72 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 17 (1) — — Sales (1) — — — Settlements (a) (27) (26) 61 4 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $17 ($1) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (17) — — Purchases 62 79 — — Sales (2) — — — Settlements (a) (42) (46) 51 34 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $6 ($17) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended September 30 2023 2022 2023 2022 Beginning balance, July 1 $41 $58 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 12 (6) — — Sales (1) — — — Settlements (a) (17) (19) 61 4 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $12 ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) — (13) — — Purchases 51 58 — — Sales (2) — — — Settlements (a) (30) (30) 51 34 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $— ($14) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended September 30 2023 2022 Beginning balance, July 1 $13 $14 Total net gains included in changes in net assets (realized/unrealized) 5 5 Settlements (10) (7) Ending balance, September 30 $8 $12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 $5 $5 WPL Commodity Contract Derivative Assets and (Liabilities), net Nine Months Ended September 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (4) Purchases 11 21 Settlements (12) (16) Ending balance, September 30 $8 $12 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 September 30 $6 ($3) (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 September 30, 2023 $3 $40 $4 $31 ($1) $9 December 31, 2022 (10) 29 (9) 25 (1) 4

Commitments And Contingencies

Commitments And Contingencies	9 Months Ended
	Sep. 30, 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $221 million, $175 million and $46 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 September 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $962 $436 $526 Coal 188 108 80 Other (a) 125 52 25 $1,275 $596 $631 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 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 September 30, 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 September 30, 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 $51 million as of September 30, 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 September 30, 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 September 30, 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 $9 - $36 $5 - $11 $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 the MISO transmission owners. Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs.
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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $221 million, $175 million and $46 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 September 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $962 $436 $526 Coal 188 108 80 Other (a) 125 52 25 $1,275 $596 $631 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 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 September 30, 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 September 30, 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 $51 million as of September 30, 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 September 30, 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 September 30, 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 $9 - $36 $5 - $11 $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 the MISO transmission owners. Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs.
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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $221 million, $175 million and $46 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 September 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $962 $436 $526 Coal 188 108 80 Other (a) 125 52 25 $1,275 $596 $631 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 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 September 30, 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 September 30, 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 $51 million as of September 30, 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 September 30, 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 September 30, 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 $9 - $36 $5 - $11 $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 the MISO transmission owners. Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs.

Segments Of Business

Segments Of Business	9 Months Ended
	Sep. 30, 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 September 30, 2023 Revenues $995 $47 $13 $1,055 $22 $1,077 Operating income (loss) 319 (4) — 315 7 322 Net income (loss) attributable to Alliant Energy common shareowners 277 (18) 259 Three Months Ended September 30, 2022 Revenues $1,039 $62 $11 $1,112 $23 $1,135 Operating income (loss) 304 (3) 1 302 7 309 Net income (loss) attributable to Alliant Energy common shareowners 245 (18) 227 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Nine Months Ended September 30, 2023 Revenues $2,562 $400 $38 $3,000 $66 $3,066 Operating income 682 48 12 742 18 760 Net income (loss) attributable to Alliant Energy common shareowners 598 (16) 582 Nine Months Ended September 30, 2022 Revenues $2,624 $418 $35 $3,077 $70 $3,147 Operating income 680 62 4 746 23 769 Net income attributable to Alliant Energy common shareowners 574 5 579 IPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $551 $31 $12 $594 Operating income (loss) 171 (2) 4 173 Net income 170 Three Months Ended September 30, 2022 Revenues $596 $33 $11 $640 Operating income (loss) 174 (3) — 171 Net income 154 Nine Months Ended September 30, 2023 Revenues $1,370 $224 $36 $1,630 Operating income 342 25 12 379 Net income 331 Nine Months Ended September 30, 2022 Revenues $1,438 $224 $34 $1,696 Operating income 353 33 3 389 Net income 327 WPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $444 $16 $1 $461 Operating income (loss) 148 (2) (4) 142 Net income 107 Three Months Ended September 30, 2022 Revenues $443 $29 $— $472 Operating income 130 — 1 131 Net income 91 Nine Months Ended September 30, 2023 Revenues $1,192 $176 $2 $1,370 Operating income 340 23 — 363 Net income 267 Nine Months Ended September 30, 2022 Revenues $1,186 $194 $1 $1,381 Operating income 327 29 1 357 Net income 247
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 September 30, 2023 Revenues $995 $47 $13 $1,055 $22 $1,077 Operating income (loss) 319 (4) — 315 7 322 Net income (loss) attributable to Alliant Energy common shareowners 277 (18) 259 Three Months Ended September 30, 2022 Revenues $1,039 $62 $11 $1,112 $23 $1,135 Operating income (loss) 304 (3) 1 302 7 309 Net income (loss) attributable to Alliant Energy common shareowners 245 (18) 227 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Nine Months Ended September 30, 2023 Revenues $2,562 $400 $38 $3,000 $66 $3,066 Operating income 682 48 12 742 18 760 Net income (loss) attributable to Alliant Energy common shareowners 598 (16) 582 Nine Months Ended September 30, 2022 Revenues $2,624 $418 $35 $3,077 $70 $3,147 Operating income 680 62 4 746 23 769 Net income attributable to Alliant Energy common shareowners 574 5 579 IPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $551 $31 $12 $594 Operating income (loss) 171 (2) 4 173 Net income 170 Three Months Ended September 30, 2022 Revenues $596 $33 $11 $640 Operating income (loss) 174 (3) — 171 Net income 154 Nine Months Ended September 30, 2023 Revenues $1,370 $224 $36 $1,630 Operating income 342 25 12 379 Net income 331 Nine Months Ended September 30, 2022 Revenues $1,438 $224 $34 $1,696 Operating income 353 33 3 389 Net income 327 WPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $444 $16 $1 $461 Operating income (loss) 148 (2) (4) 142 Net income 107 Three Months Ended September 30, 2022 Revenues $443 $29 $— $472 Operating income 130 — 1 131 Net income 91 Nine Months Ended September 30, 2023 Revenues $1,192 $176 $2 $1,370 Operating income 340 23 — 363 Net income 267 Nine Months Ended September 30, 2022 Revenues $1,186 $194 $1 $1,381 Operating income 327 29 1 357 Net income 247
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 September 30, 2023 Revenues $995 $47 $13 $1,055 $22 $1,077 Operating income (loss) 319 (4) — 315 7 322 Net income (loss) attributable to Alliant Energy common shareowners 277 (18) 259 Three Months Ended September 30, 2022 Revenues $1,039 $62 $11 $1,112 $23 $1,135 Operating income (loss) 304 (3) 1 302 7 309 Net income (loss) attributable to Alliant Energy common shareowners 245 (18) 227 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Nine Months Ended September 30, 2023 Revenues $2,562 $400 $38 $3,000 $66 $3,066 Operating income 682 48 12 742 18 760 Net income (loss) attributable to Alliant Energy common shareowners 598 (16) 582 Nine Months Ended September 30, 2022 Revenues $2,624 $418 $35 $3,077 $70 $3,147 Operating income 680 62 4 746 23 769 Net income attributable to Alliant Energy common shareowners 574 5 579 IPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $551 $31 $12 $594 Operating income (loss) 171 (2) 4 173 Net income 170 Three Months Ended September 30, 2022 Revenues $596 $33 $11 $640 Operating income (loss) 174 (3) — 171 Net income 154 Nine Months Ended September 30, 2023 Revenues $1,370 $224 $36 $1,630 Operating income 342 25 12 379 Net income 331 Nine Months Ended September 30, 2022 Revenues $1,438 $224 $34 $1,696 Operating income 353 33 3 389 Net income 327 WPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $444 $16 $1 $461 Operating income (loss) 148 (2) (4) 142 Net income 107 Three Months Ended September 30, 2022 Revenues $443 $29 $— $472 Operating income 130 — 1 131 Net income 91 Nine Months Ended September 30, 2023 Revenues $1,192 $176 $2 $1,370 Operating income 340 23 — 363 Net income 267 Nine Months Ended September 30, 2022 Revenues $1,186 $194 $1 $1,381 Operating income 327 29 1 357 Net income 247

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 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 and nine months ended September 30 were as follows (in millions): IPL WPL Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $46 $45 $134 $136 $40 $39 $120 $117 Sales credited 3 11 11 11 23 31 45 62 Purchases billed 133 119 320 342 5 42 21 103 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL September 30, 2023 December 31, 2022 September 30, 2023 December 31, 2022 Net payables to Corporate Services $136 $103 $71 $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 and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 ATC billings to WPL $41 $38 $119 $107 WPL billings to ATC 5 6 16 14 WPL owed ATC net amounts of $9 million as of September 30, 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 and nine months ended September 30 were as follows (in millions): IPL WPL Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $46 $45 $134 $136 $40 $39 $120 $117 Sales credited 3 11 11 11 23 31 45 62 Purchases billed 133 119 320 342 5 42 21 103 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL September 30, 2023 December 31, 2022 September 30, 2023 December 31, 2022 Net payables to Corporate Services $136 $103 $71 $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 and nine months ended September 30 were as follows (in millions): IPL WPL Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $46 $45 $134 $136 $40 $39 $120 $117 Sales credited 3 11 11 11 23 31 45 62 Purchases billed 133 119 320 342 5 42 21 103 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL September 30, 2023 December 31, 2022 September 30, 2023 December 31, 2022 Net payables to Corporate Services $136 $103 $71 $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 and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 ATC billings to WPL $41 $38 $119 $107 WPL billings to ATC 5 6 16 14 WPL owed ATC net amounts of $9 million as of September 30, 2023 and $10 million as of December 31, 2022.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net income	$ 582	$ 579

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policy)	9 Months Ended
	Sep. 30, 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $189 million, $180 million and $9 million of money market fund investments, respectively, with weighted average 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $189 million, $180 million and $9 million of money market fund investments, respectively, with weighted average 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 September 30, 2023, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $189 million, $180 million and $9 million of money market fund investments, respectively, with weighted average interest rates of 5%.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2023
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $919 $929 $825 $848 $94 $81 Pension and OPEB costs 371 392 187 197 184 195 Assets retired early 282 70 267 53 15 17 Asset retirement obligations (AROs) 199 151 155 110 44 41 Commodity cost recovery 138 160 11 1 127 159 Derivatives 72 84 27 48 45 36 IPL’s Duane Arnold Energy Center PPA amendment 48 66 48 66 — — WPL’s Western Wisconsin gas distribution expansion investments 46 48 — — 46 48 Other 194 146 70 63 124 83 $2,269 $2,046 $1,590 $1,386 $679 $660
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $569 $579 $301 $303 $268 $276 Cost of removal obligations 397 398 249 259 148 139 Derivatives 91 210 52 115 39 95 Commodity cost recovery 41 40 11 38 30 2 WPL’s West Riverside liquidated damages 9 32 — — 9 32 Electric transmission cost recovery 6 20 6 10 — 10 Other 74 45 36 29 38 16 $1,187 $1,324 $655 $754 $532 $570
IPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $919 $929 $825 $848 $94 $81 Pension and OPEB costs 371 392 187 197 184 195 Assets retired early 282 70 267 53 15 17 Asset retirement obligations (AROs) 199 151 155 110 44 41 Commodity cost recovery 138 160 11 1 127 159 Derivatives 72 84 27 48 45 36 IPL’s Duane Arnold Energy Center PPA amendment 48 66 48 66 — — WPL’s Western Wisconsin gas distribution expansion investments 46 48 — — 46 48 Other 194 146 70 63 124 83 $2,269 $2,046 $1,590 $1,386 $679 $660
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $569 $579 $301 $303 $268 $276 Cost of removal obligations 397 398 249 259 148 139 Derivatives 91 210 52 115 39 95 Commodity cost recovery 41 40 11 38 30 2 WPL’s West Riverside liquidated damages 9 32 — — 9 32 Electric transmission cost recovery 6 20 6 10 — 10 Other 74 45 36 29 38 16 $1,187 $1,324 $655 $754 $532 $570
WPL [Member]
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $919 $929 $825 $848 $94 $81 Pension and OPEB costs 371 392 187 197 184 195 Assets retired early 282 70 267 53 15 17 Asset retirement obligations (AROs) 199 151 155 110 44 41 Commodity cost recovery 138 160 11 1 127 159 Derivatives 72 84 27 48 45 36 IPL’s Duane Arnold Energy Center PPA amendment 48 66 48 66 — — WPL’s Western Wisconsin gas distribution expansion investments 46 48 — — 46 48 Other 194 146 70 63 124 83 $2,269 $2,046 $1,590 $1,386 $679 $660
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL September 30, December 31, September 30, December 31, September 30, December 31, Tax-related $569 $579 $301 $303 $268 $276 Cost of removal obligations 397 398 249 259 148 139 Derivatives 91 210 52 115 39 95 Commodity cost recovery 41 40 11 38 30 2 WPL’s West Riverside liquidated damages 9 32 — — 9 32 Electric transmission cost recovery 6 20 6 10 — 10 Other 74 45 36 29 38 16 $1,187 $1,324 $655 $754 $532 $570

Receivables (Tables)

Receivables (Tables)	9 Months Ended
	Sep. 30, 2023
Receivables [Line Items]
Gross Write-offs For Accounts Receivable	For the three and nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable were as follows (in millions): Originated in 2022 Originated in 2023 Three Months Nine Months Three Months Nine Months Alliant Energy $3 $11 $6 $8 IPL 2 7 4 5 WPL 1 4 2 3
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 and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $94 $36 $110 $66 Average outstanding aggregate cash proceeds 46 3 68 8
Attributes of Receivables Sold Under the Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): September 30, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 88 132 Other receivables 1 — Receivables sold to third party 250 277 Less: cash proceeds 1 80 Deferred proceeds 249 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $236 $185
Additional Attributes Of Receivables Sold Under The Receivables Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Collections $616 $670 $1,720 $1,731 Write-offs, net of recoveries 5 3 9 6
IPL [Member]
Receivables [Line Items]
Gross Write-offs For Accounts Receivable	For the three and nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable were as follows (in millions): Originated in 2022 Originated in 2023 Three Months Nine Months Three Months Nine Months Alliant Energy $3 $11 $6 $8 IPL 2 7 4 5 WPL 1 4 2 3
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 and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $94 $36 $110 $66 Average outstanding aggregate cash proceeds 46 3 68 8
Attributes of Receivables Sold Under the Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): September 30, 2023 December 31, 2022 Customer accounts receivable $161 $145 Unbilled utility revenues 88 132 Other receivables 1 — Receivables sold to third party 250 277 Less: cash proceeds 1 80 Deferred proceeds 249 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $236 $185
Additional Attributes Of Receivables Sold Under The Receivables Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 Collections $616 $670 $1,720 $1,731 Write-offs, net of recoveries 5 3 9 6
WPL [Member]
Receivables [Line Items]
Gross Write-offs For Accounts Receivable	For the three and nine months ended September 30, 2023, Alliant Energy’s, IPL’s and WPL’s gross write-offs for accounts receivable were as follows (in millions): Originated in 2022 Originated in 2023 Three Months Nine Months Three Months Nine Months Alliant Energy $3 $11 $6 $8 IPL 2 7 4 5 WPL 1 4 2 3

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 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 and nine months ended September 30 was as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 ATC Holdings ($12) ($7) ($37) ($29) Other (2) 2 (8) (8) ($14) ($5) ($45) ($37)

Common Equity (Tables)

Common Equity (Tables)	9 Months Ended
	Sep. 30, 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 At-the-market offering program 3,569,937 Shareowner Direct Plan 339,850 Equity-based compensation plans 134,334 Shares outstanding, September 30, 2023 255,179,087
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Net income attributable to Alliant Energy common shareowners 259 259 Common stock dividends ($0.4525 per share) (115) (115) At-the-market offering program and Shareowner Direct Plan issuances 125 125 Equity-based compensation plans and other 3 1 4 Other comprehensive income, net of tax 1 1 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 Net income attributable to Alliant Energy common shareowners 227 227 Common stock dividends ($0.4275 per share) (106) (106) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 2 (1) 1 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 582 582 Common stock dividends ($1.3575 per share) (341) (341) At-the-market offering program and Shareowner Direct Plan issuances 201 201 Equity-based compensation plans and other 4 4 Other comprehensive income, net of tax 4 4 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 579 579 Common stock dividends ($1.2825 per share) (322) (322) Shareowner Direct Plan issuances 19 19 Equity-based compensation plans and other (1) 1 (1) (1) Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $33 $2,847 $989 $3,869 Net income 170 170 Common stock dividends (70) (70) Capital contributions from parent 20 20 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $33 $2,807 $942 $3,782 Net income 154 154 Common stock dividends (80) (80) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 331 331 Common stock dividends (210) (210) Capital contributions from parent 60 60 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 327 327 Common stock dividends (240) (240) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Net income 107 107 Common stock dividends (46) (46) Capital contributions from parent 65 65 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 Net income 91 91 Common stock dividends (44) (44) Capital contributions from parent 155 155 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 267 267 Common stock dividends (138) (138) Capital contributions from parent 245 245 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 247 247 Common stock dividends (133) (133) Capital contributions from parent 420 420 Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Other (1) (1) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356
IPL [Member]
Schedule of Capitalization, Equity [Line Items]
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Net income attributable to Alliant Energy common shareowners 259 259 Common stock dividends ($0.4525 per share) (115) (115) At-the-market offering program and Shareowner Direct Plan issuances 125 125 Equity-based compensation plans and other 3 1 4 Other comprehensive income, net of tax 1 1 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 Net income attributable to Alliant Energy common shareowners 227 227 Common stock dividends ($0.4275 per share) (106) (106) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 2 (1) 1 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 582 582 Common stock dividends ($1.3575 per share) (341) (341) At-the-market offering program and Shareowner Direct Plan issuances 201 201 Equity-based compensation plans and other 4 4 Other comprehensive income, net of tax 4 4 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 579 579 Common stock dividends ($1.2825 per share) (322) (322) Shareowner Direct Plan issuances 19 19 Equity-based compensation plans and other (1) 1 (1) (1) Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $33 $2,847 $989 $3,869 Net income 170 170 Common stock dividends (70) (70) Capital contributions from parent 20 20 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $33 $2,807 $942 $3,782 Net income 154 154 Common stock dividends (80) (80) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 331 331 Common stock dividends (210) (210) Capital contributions from parent 60 60 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 327 327 Common stock dividends (240) (240) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Net income 107 107 Common stock dividends (46) (46) Capital contributions from parent 65 65 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 Net income 91 91 Common stock dividends (44) (44) Capital contributions from parent 155 155 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 267 267 Common stock dividends (138) (138) Capital contributions from parent 245 245 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 247 247 Common stock dividends (133) (133) Capital contributions from parent 420 420 Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Other (1) (1) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356
WPL [Member]
Schedule of Capitalization, Equity [Line Items]
Changes in Shareowners' Equity	A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Net income attributable to Alliant Energy common shareowners 259 259 Common stock dividends ($0.4525 per share) (115) (115) At-the-market offering program and Shareowner Direct Plan issuances 125 125 Equity-based compensation plans and other 3 1 4 Other comprehensive income, net of tax 1 1 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 Net income attributable to Alliant Energy common shareowners 227 227 Common stock dividends ($0.4275 per share) (106) (106) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 2 (1) 1 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 Alliant Energy Total Alliant Energy Common Equity Accumulated Shares in Additional Other Deferred Common Paid-In Retained Comprehensive Compensation Noncontrolling Total Stock Capital Earnings Income Trust Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 582 582 Common stock dividends ($1.3575 per share) (341) (341) At-the-market offering program and Shareowner Direct Plan issuances 201 201 Equity-based compensation plans and other 4 4 Other comprehensive income, net of tax 4 4 Ending balance, September 30, 2023 $3 $2,982 $3,750 $4 ($13) $— $6,726 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 579 579 Common stock dividends ($1.2825 per share) (322) (322) Shareowner Direct Plan issuances 19 19 Equity-based compensation plans and other (1) 1 (1) (1) Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $3 $2,767 $3,508 $— ($13) $— $6,265 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $33 $2,847 $989 $3,869 Net income 170 170 Common stock dividends (70) (70) Capital contributions from parent 20 20 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $33 $2,807 $942 $3,782 Net income 154 154 Common stock dividends (80) (80) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 331 331 Common stock dividends (210) (210) Capital contributions from parent 60 60 Ending balance, September 30, 2023 $33 $2,867 $1,089 $3,989 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 327 327 Common stock dividends (240) (240) Ending balance, September 30, 2022 $33 $2,807 $1,016 $3,856 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended September 30, 2023 Beginning balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Net income 107 107 Common stock dividends (46) (46) Capital contributions from parent 65 65 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Three Months Ended September 30, 2022 Beginning balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 Net income 91 91 Common stock dividends (44) (44) Capital contributions from parent 155 155 Distributions to noncontrolling interest (29) (29) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Nine Months Ended September 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 267 267 Common stock dividends (138) (138) Capital contributions from parent 245 245 Ending balance, September 30, 2023 $66 $2,478 $1,321 $— $3,865 Nine Months Ended September 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 247 247 Common stock dividends (133) (133) Capital contributions from parent 420 420 Contributions from noncontrolling interest 29 29 Distributions to noncontrolling interest (29) (29) Other (1) (1) Ending balance, September 30, 2022 $66 $2,123 $1,167 $— $3,356

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 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): September 30, 2023 Alliant Energy IPL WPL Amount outstanding $451 $— $120 Weighted average interest rates 5.5% —% 5.4% Available credit facility capacity $549 $250 $180 Alliant Energy IPL WPL Three Months Ended September 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $474 $449 $7 $— $125 $251 Average amount outstanding (based on daily outstanding balances) $440 $353 $— $— $86 $110 Weighted average interest rates 5.5% 2.4% 5.5% —% 5.4% 2.0% Nine Months Ended September 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $367 $377 $2 $— $135 $160 Weighted average interest rates 5.1% 1.2% 5.3% —% 4.9% 0.9%
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): September 30, 2023 Alliant Energy IPL WPL Amount outstanding $451 $— $120 Weighted average interest rates 5.5% —% 5.4% Available credit facility capacity $549 $250 $180 Alliant Energy IPL WPL Three Months Ended September 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $474 $449 $7 $— $125 $251 Average amount outstanding (based on daily outstanding balances) $440 $353 $— $— $86 $110 Weighted average interest rates 5.5% 2.4% 5.5% —% 5.4% 2.0% Nine Months Ended September 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $367 $377 $2 $— $135 $160 Weighted average interest rates 5.1% 1.2% 5.3% —% 4.9% 0.9%
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): September 30, 2023 Alliant Energy IPL WPL Amount outstanding $451 $— $120 Weighted average interest rates 5.5% —% 5.4% Available credit facility capacity $549 $250 $180 Alliant Energy IPL WPL Three Months Ended September 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $474 $449 $7 $— $125 $251 Average amount outstanding (based on daily outstanding balances) $440 $353 $— $— $86 $110 Weighted average interest rates 5.5% 2.4% 5.5% —% 5.4% 2.0% Nine Months Ended September 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $367 $377 $2 $— $135 $160 Weighted average interest rates 5.1% 1.2% 5.3% —% 4.9% 0.9%

Revenues (Tables)

Revenues (Tables)	9 Months Ended
	Sep. 30, 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 September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $374 $376 $209 $222 $165 $154 Retail - commercial 241 243 158 165 83 78 Retail - industrial 280 289 153 172 127 117 Wholesale 59 68 21 19 38 49 Bulk power and other 41 63 10 18 31 45 Total Electric Utility 995 1,039 551 596 444 443 Gas Utility: Retail - residential 23 28 14 14 9 14 Retail - commercial 12 18 9 8 3 10 Retail - industrial 2 4 2 3 — 1 Transportation/other 10 12 6 8 4 4 Total Gas Utility 47 62 31 33 16 29 Other Utility: Steam 11 9 11 9 — — Other utility 2 2 1 2 1 — Total Other Utility 13 11 12 11 1 — Non-Utility and Other: Travero and other 22 23 — — — — Total Non-Utility and Other 22 23 — — — — Total revenues $1,077 $1,135 $594 $640 $461 $472 Alliant Energy IPL WPL Nine Months Ended September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $943 $956 $503 $529 $440 $427 Retail - commercial 627 628 399 411 228 217 Retail - industrial 740 743 389 418 351 325 Wholesale 154 168 47 49 107 119 Bulk power and other 98 129 32 31 66 98 Total Electric Utility 2,562 2,624 1,370 1,438 1,192 1,186 Gas Utility: Retail - residential 233 237 131 127 102 110 Retail - commercial 122 127 65 62 57 65 Retail - industrial 12 15 8 10 4 5 Transportation/other 33 39 20 25 13 14 Total Gas Utility 400 418 224 224 176 194 Other Utility: Steam 32 29 32 29 — — Other utility 6 6 4 5 2 1 Total Other Utility 38 35 36 34 2 1 Non-Utility and Other: Travero and other 66 70 — — — — Total Non-Utility and Other 66 70 — — — — Total revenues $3,066 $3,147 $1,630 $1,696 $1,370 $1,381
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 September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $374 $376 $209 $222 $165 $154 Retail - commercial 241 243 158 165 83 78 Retail - industrial 280 289 153 172 127 117 Wholesale 59 68 21 19 38 49 Bulk power and other 41 63 10 18 31 45 Total Electric Utility 995 1,039 551 596 444 443 Gas Utility: Retail - residential 23 28 14 14 9 14 Retail - commercial 12 18 9 8 3 10 Retail - industrial 2 4 2 3 — 1 Transportation/other 10 12 6 8 4 4 Total Gas Utility 47 62 31 33 16 29 Other Utility: Steam 11 9 11 9 — — Other utility 2 2 1 2 1 — Total Other Utility 13 11 12 11 1 — Non-Utility and Other: Travero and other 22 23 — — — — Total Non-Utility and Other 22 23 — — — — Total revenues $1,077 $1,135 $594 $640 $461 $472 Alliant Energy IPL WPL Nine Months Ended September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $943 $956 $503 $529 $440 $427 Retail - commercial 627 628 399 411 228 217 Retail - industrial 740 743 389 418 351 325 Wholesale 154 168 47 49 107 119 Bulk power and other 98 129 32 31 66 98 Total Electric Utility 2,562 2,624 1,370 1,438 1,192 1,186 Gas Utility: Retail - residential 233 237 131 127 102 110 Retail - commercial 122 127 65 62 57 65 Retail - industrial 12 15 8 10 4 5 Transportation/other 33 39 20 25 13 14 Total Gas Utility 400 418 224 224 176 194 Other Utility: Steam 32 29 32 29 — — Other utility 6 6 4 5 2 1 Total Other Utility 38 35 36 34 2 1 Non-Utility and Other: Travero and other 66 70 — — — — Total Non-Utility and Other 66 70 — — — — Total revenues $3,066 $3,147 $1,630 $1,696 $1,370 $1,381
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 September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $374 $376 $209 $222 $165 $154 Retail - commercial 241 243 158 165 83 78 Retail - industrial 280 289 153 172 127 117 Wholesale 59 68 21 19 38 49 Bulk power and other 41 63 10 18 31 45 Total Electric Utility 995 1,039 551 596 444 443 Gas Utility: Retail - residential 23 28 14 14 9 14 Retail - commercial 12 18 9 8 3 10 Retail - industrial 2 4 2 3 — 1 Transportation/other 10 12 6 8 4 4 Total Gas Utility 47 62 31 33 16 29 Other Utility: Steam 11 9 11 9 — — Other utility 2 2 1 2 1 — Total Other Utility 13 11 12 11 1 — Non-Utility and Other: Travero and other 22 23 — — — — Total Non-Utility and Other 22 23 — — — — Total revenues $1,077 $1,135 $594 $640 $461 $472 Alliant Energy IPL WPL Nine Months Ended September 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $943 $956 $503 $529 $440 $427 Retail - commercial 627 628 399 411 228 217 Retail - industrial 740 743 389 418 351 325 Wholesale 154 168 47 49 107 119 Bulk power and other 98 129 32 31 66 98 Total Electric Utility 2,562 2,624 1,370 1,438 1,192 1,186 Gas Utility: Retail - residential 233 237 131 127 102 110 Retail - commercial 122 127 65 62 57 65 Retail - industrial 12 15 8 10 4 5 Transportation/other 33 39 20 25 13 14 Total Gas Utility 400 418 224 224 176 194 Other Utility: Steam 32 29 32 29 — — Other utility 6 6 4 5 2 1 Total Other Utility 38 35 36 34 2 1 Non-Utility and Other: Travero and other 66 70 — — — — Total Non-Utility and Other 66 70 — — — — Total revenues $3,066 $3,147 $1,630 $1,696 $1,370 $1,381

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2023
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates for the three and nine months ended September 30, 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 Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate 2% 6% 1% 4% (22%) (12%) (20%) (14%) 16% 15% 15% 17%
Summary Of Tax Credit Carryforwards	At September 30, 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 $431 $6 $1 Federal tax credits 2031-2043 737 520 208
IPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates for the three and nine months ended September 30, 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 Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate 2% 6% 1% 4% (22%) (12%) (20%) (14%) 16% 15% 15% 17%
Summary Of Tax Credit Carryforwards	At September 30, 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 $431 $6 $1 Federal tax credits 2031-2043 737 520 208
WPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates for the three and nine months ended September 30, 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 Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate 2% 6% 1% 4% (22%) (12%) (20%) (14%) 16% 15% 15% 17%
Summary Of Tax Credit Carryforwards	At September 30, 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 $431 $6 $1 Federal tax credits 2031-2043 737 520 208

Benefit Plans (Tables)

Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 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 and nine months ended September 30 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 Three Months Nine Months Three Months Nine Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $2 $3 $4 $7 $1 $— $2 $2 Interest cost 12 9 35 27 3 1 7 4 Expected return on plan assets (14) (18) (40) (52) (2) — (4) (3) Amortization of prior service credit (1) — (1) — — — — — Amortization of actuarial loss 7 8 21 24 — 1 1 2 $6 $2 $19 $6 $2 $2 $6 $5 Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $1 $2 $4 $— $— $— $1 Interest cost 6 4 16 12 1 1 3 2 Expected return on plan assets (6) (7) (19) (23) (1) (1) (3) (3) Amortization of actuarial loss 2 3 8 10 — — 1 — $2 $1 $7 $3 $— $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $— $1 $2 $1 $— $1 $— Interest cost 5 4 15 12 1 1 3 2 Expected return on plan assets (5) (7) (16) (23) (1) — (1) — Amortization of actuarial loss 3 4 10 12 — — — 1 $3 $1 $10 $3 $1 $1 $3 $3
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 and nine months ended September 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $4 $3 $10 $9 $2 $2 $5 $5 $2 $1 $4 $4 Income tax benefits 1 1 3 3 1 — 1 1 — — 1 1
Schedule Of Equity-based Compensation Plans Activity	For the nine months ended September 30, 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 108,513 $55.68 Performance restricted stock units 123,990 52.71 Restricted stock units 105,982 52.77
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 and nine months ended September 30 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 Three Months Nine Months Three Months Nine Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $2 $3 $4 $7 $1 $— $2 $2 Interest cost 12 9 35 27 3 1 7 4 Expected return on plan assets (14) (18) (40) (52) (2) — (4) (3) Amortization of prior service credit (1) — (1) — — — — — Amortization of actuarial loss 7 8 21 24 — 1 1 2 $6 $2 $19 $6 $2 $2 $6 $5 Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $1 $2 $4 $— $— $— $1 Interest cost 6 4 16 12 1 1 3 2 Expected return on plan assets (6) (7) (19) (23) (1) (1) (3) (3) Amortization of actuarial loss 2 3 8 10 — — 1 — $2 $1 $7 $3 $— $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $— $1 $2 $1 $— $1 $— Interest cost 5 4 15 12 1 1 3 2 Expected return on plan assets (5) (7) (16) (23) (1) — (1) — Amortization of actuarial loss 3 4 10 12 — — — 1 $3 $1 $10 $3 $1 $1 $3 $3
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 and nine months ended September 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $4 $3 $10 $9 $2 $2 $5 $5 $2 $1 $4 $4 Income tax benefits 1 1 3 3 1 — 1 1 — — 1 1
Schedule Of Equity-based Compensation Plans Activity	For the nine months ended September 30, 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 108,513 $55.68 Performance restricted stock units 123,990 52.71 Restricted stock units 105,982 52.77
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 and nine months ended September 30 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 Three Months Nine Months Three Months Nine Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $2 $3 $4 $7 $1 $— $2 $2 Interest cost 12 9 35 27 3 1 7 4 Expected return on plan assets (14) (18) (40) (52) (2) — (4) (3) Amortization of prior service credit (1) — (1) — — — — — Amortization of actuarial loss 7 8 21 24 — 1 1 2 $6 $2 $19 $6 $2 $2 $6 $5 Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $1 $2 $4 $— $— $— $1 Interest cost 6 4 16 12 1 1 3 2 Expected return on plan assets (6) (7) (19) (23) (1) (1) (3) (3) Amortization of actuarial loss 2 3 8 10 — — 1 — $2 $1 $7 $3 $— $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Nine Months Three Months Nine Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $— $— $1 $2 $1 $— $1 $— Interest cost 5 4 15 12 1 1 3 2 Expected return on plan assets (5) (7) (16) (23) (1) — (1) — Amortization of actuarial loss 3 4 10 12 — — — 1 $3 $1 $10 $3 $1 $1 $3 $3
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 and nine months ended September 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Nine Months Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $4 $3 $10 $9 $2 $2 $5 $5 $2 $1 $4 $4 Income tax benefits 1 1 3 3 1 — 1 1 — — 1 1
Schedule Of Equity-based Compensation Plans Activity	For the nine months ended September 30, 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 108,513 $55.68 Performance restricted stock units 123,990 52.71 Restricted stock units 105,982 52.77

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2023
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of September 30, 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 1,661 2023-2026 18,122 2023-2024 180,519 2023-2032 370 2023 IPL 746 2023-2026 8,078 2023-2024 85,457 2023-2030 217 2023 WPL 915 2023-2026 10,044 2023-2024 95,062 2023-2032 153 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 September 30, December 31, September 30, December 31, September 30, December 31, Current derivative assets $67 $111 $51 $69 $16 $42 Non-current derivative assets 62 126 34 69 28 57 Current derivative liabilities 32 59 15 40 17 19 Non-current derivative liabilities 34 20 6 6 28 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 September 30, 2023 Derivative assets $129 $108 $85 $73 $44 $35 Derivative liabilities 66 45 21 9 45 36 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 September 30, 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 1,661 2023-2026 18,122 2023-2024 180,519 2023-2032 370 2023 IPL 746 2023-2026 8,078 2023-2024 85,457 2023-2030 217 2023 WPL 915 2023-2026 10,044 2023-2024 95,062 2023-2032 153 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 September 30, December 31, September 30, December 31, September 30, December 31, Current derivative assets $67 $111 $51 $69 $16 $42 Non-current derivative assets 62 126 34 69 28 57 Current derivative liabilities 32 59 15 40 17 19 Non-current derivative liabilities 34 20 6 6 28 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 September 30, 2023 Derivative assets $129 $108 $85 $73 $44 $35 Derivative liabilities 66 45 21 9 45 36 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 September 30, 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 1,661 2023-2026 18,122 2023-2024 180,519 2023-2032 370 2023 IPL 746 2023-2026 8,078 2023-2024 85,457 2023-2030 217 2023 WPL 915 2023-2026 10,044 2023-2024 95,062 2023-2032 153 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 September 30, December 31, September 30, December 31, September 30, December 31, Current derivative assets $67 $111 $51 $69 $16 $42 Non-current derivative assets 62 126 34 69 28 57 Current derivative liabilities 32 59 15 40 17 19 Non-current derivative liabilities 34 20 6 6 28 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 September 30, 2023 Derivative assets $129 $108 $85 $73 $44 $35 Derivative liabilities 66 45 21 9 45 36 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)	9 Months Ended
	Sep. 30, 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 September 30, 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 $189 $189 $— $— $189 $10 $10 $— $— $10 Commodity derivatives 129 — 80 49 129 237 — 206 31 237 Interest rate derivatives 6 — 6 — 6 — — — — — Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 66 — 60 6 66 79 — 67 12 79 Long-term debt (incl. current maturities) 8,838 — 7,863 — 7,863 8,076 — 7,338 1 7,339 IPL September 30, 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 $180 $180 $— $— $180 $10 $10 $— $— $10 Commodity derivatives 85 — 45 40 85 138 — 111 27 138 Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 21 — 16 5 21 46 — 35 11 46 Long-term debt 3,944 — 3,422 — 3,422 3,646 — 3,228 — 3,228 WPL September 30, 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: Commodity derivatives $44 $— $35 $9 $44 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 45 — 44 1 45 33 — 32 1 33 Long-term debt 3,069 — 2,722 — 2,722 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 September 30 2023 2022 2023 2022 Beginning balance, July 1 $54 $72 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 17 (1) — — Sales (1) — — — Settlements (a) (27) (26) 61 4 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $17 ($1) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (17) — — Purchases 62 79 — — Sales (2) — — — Settlements (a) (42) (46) 51 34 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $6 ($17) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended September 30 2023 2022 2023 2022 Beginning balance, July 1 $41 $58 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 12 (6) — — Sales (1) — — — Settlements (a) (17) (19) 61 4 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $12 ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) — (13) — — Purchases 51 58 — — Sales (2) — — — Settlements (a) (30) (30) 51 34 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $— ($14) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended September 30 2023 2022 Beginning balance, July 1 $13 $14 Total net gains included in changes in net assets (realized/unrealized) 5 5 Settlements (10) (7) Ending balance, September 30 $8 $12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 $5 $5 WPL Commodity Contract Derivative Assets and (Liabilities), net Nine Months Ended September 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (4) Purchases 11 21 Settlements (12) (16) Ending balance, September 30 $8 $12 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 September 30 $6 ($3) (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 September 30, 2023 $3 $40 $4 $31 ($1) $9 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 September 30, 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 $189 $189 $— $— $189 $10 $10 $— $— $10 Commodity derivatives 129 — 80 49 129 237 — 206 31 237 Interest rate derivatives 6 — 6 — 6 — — — — — Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 66 — 60 6 66 79 — 67 12 79 Long-term debt (incl. current maturities) 8,838 — 7,863 — 7,863 8,076 — 7,338 1 7,339 IPL September 30, 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 $180 $180 $— $— $180 $10 $10 $— $— $10 Commodity derivatives 85 — 45 40 85 138 — 111 27 138 Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 21 — 16 5 21 46 — 35 11 46 Long-term debt 3,944 — 3,422 — 3,422 3,646 — 3,228 — 3,228 WPL September 30, 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: Commodity derivatives $44 $— $35 $9 $44 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 45 — 44 1 45 33 — 32 1 33 Long-term debt 3,069 — 2,722 — 2,722 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 September 30 2023 2022 2023 2022 Beginning balance, July 1 $54 $72 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 17 (1) — — Sales (1) — — — Settlements (a) (27) (26) 61 4 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $17 ($1) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (17) — — Purchases 62 79 — — Sales (2) — — — Settlements (a) (42) (46) 51 34 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $6 ($17) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended September 30 2023 2022 2023 2022 Beginning balance, July 1 $41 $58 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 12 (6) — — Sales (1) — — — Settlements (a) (17) (19) 61 4 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $12 ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) — (13) — — Purchases 51 58 — — Sales (2) — — — Settlements (a) (30) (30) 51 34 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $— ($14) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended September 30 2023 2022 Beginning balance, July 1 $13 $14 Total net gains included in changes in net assets (realized/unrealized) 5 5 Settlements (10) (7) Ending balance, September 30 $8 $12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 $5 $5 WPL Commodity Contract Derivative Assets and (Liabilities), net Nine Months Ended September 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (4) Purchases 11 21 Settlements (12) (16) Ending balance, September 30 $8 $12 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 September 30 $6 ($3) (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 September 30, 2023 $3 $40 $4 $31 ($1) $9 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 September 30, 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 $189 $189 $— $— $189 $10 $10 $— $— $10 Commodity derivatives 129 — 80 49 129 237 — 206 31 237 Interest rate derivatives 6 — 6 — 6 — — — — — Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 66 — 60 6 66 79 — 67 12 79 Long-term debt (incl. current maturities) 8,838 — 7,863 — 7,863 8,076 — 7,338 1 7,339 IPL September 30, 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 $180 $180 $— $— $180 $10 $10 $— $— $10 Commodity derivatives 85 — 45 40 85 138 — 111 27 138 Deferred proceeds 236 — — 236 236 185 — — 185 185 Liabilities: Commodity derivatives 21 — 16 5 21 46 — 35 11 46 Long-term debt 3,944 — 3,422 — 3,422 3,646 — 3,228 — 3,228 WPL September 30, 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: Commodity derivatives $44 $— $35 $9 $44 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 45 — 44 1 45 33 — 32 1 33 Long-term debt 3,069 — 2,722 — 2,722 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 September 30 2023 2022 2023 2022 Beginning balance, July 1 $54 $72 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 17 (1) — — Sales (1) — — — Settlements (a) (27) (26) 61 4 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $17 ($1) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (17) — — Purchases 62 79 — — Sales (2) — — — Settlements (a) (42) (46) 51 34 Ending balance, September 30 $43 $45 $236 $248 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 September 30 $6 ($17) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended September 30 2023 2022 2023 2022 Beginning balance, July 1 $41 $58 $175 $244 Total net gains (losses) included in changes in net assets (realized/unrealized) 12 (6) — — Sales (1) — — — Settlements (a) (17) (19) 61 4 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $12 ($6) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Nine Months Ended September 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) — (13) — — Purchases 51 58 — — Sales (2) — — — Settlements (a) (30) (30) 51 34 Ending balance, September 30 $35 $33 $236 $248 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 September 30 $— ($14) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended September 30 2023 2022 Beginning balance, July 1 $13 $14 Total net gains included in changes in net assets (realized/unrealized) 5 5 Settlements (10) (7) Ending balance, September 30 $8 $12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at September 30 $5 $5 WPL Commodity Contract Derivative Assets and (Liabilities), net Nine Months Ended September 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (4) Purchases 11 21 Settlements (12) (16) Ending balance, September 30 $8 $12 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 September 30 $6 ($3) (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 September 30, 2023 $3 $40 $4 $31 ($1) $9 December 31, 2022 (10) 29 (9) 25 (1) 4

Commitments And Contingencies (

Commitments And Contingencies (Tables)	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At September 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $962 $436 $526 Coal 188 108 80 Other (a) 125 52 25 $1,275 $596 $631 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At September 30, 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 $9 - $36 $5 - $11 $4 - $25 Current and non-current environmental liabilities $18 $8 $10
IPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At September 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $962 $436 $526 Coal 188 108 80 Other (a) 125 52 25 $1,275 $596 $631 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At September 30, 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 $9 - $36 $5 - $11 $4 - $25 Current and non-current environmental liabilities $18 $8 $10
WPL [Member]
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At September 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $962 $436 $526 Coal 188 108 80 Other (a) 125 52 25 $1,275 $596 $631 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At September 30, 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 $9 - $36 $5 - $11 $4 - $25 Current and non-current environmental liabilities $18 $8 $10

Segments Of Business (Tables)

Segments Of Business (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2023 Revenues $995 $47 $13 $1,055 $22 $1,077 Operating income (loss) 319 (4) — 315 7 322 Net income (loss) attributable to Alliant Energy common shareowners 277 (18) 259 Three Months Ended September 30, 2022 Revenues $1,039 $62 $11 $1,112 $23 $1,135 Operating income (loss) 304 (3) 1 302 7 309 Net income (loss) attributable to Alliant Energy common shareowners 245 (18) 227 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Nine Months Ended September 30, 2023 Revenues $2,562 $400 $38 $3,000 $66 $3,066 Operating income 682 48 12 742 18 760 Net income (loss) attributable to Alliant Energy common shareowners 598 (16) 582 Nine Months Ended September 30, 2022 Revenues $2,624 $418 $35 $3,077 $70 $3,147 Operating income 680 62 4 746 23 769 Net income attributable to Alliant Energy common shareowners 574 5 579 IPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $551 $31 $12 $594 Operating income (loss) 171 (2) 4 173 Net income 170 Three Months Ended September 30, 2022 Revenues $596 $33 $11 $640 Operating income (loss) 174 (3) — 171 Net income 154 Nine Months Ended September 30, 2023 Revenues $1,370 $224 $36 $1,630 Operating income 342 25 12 379 Net income 331 Nine Months Ended September 30, 2022 Revenues $1,438 $224 $34 $1,696 Operating income 353 33 3 389 Net income 327 WPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $444 $16 $1 $461 Operating income (loss) 148 (2) (4) 142 Net income 107 Three Months Ended September 30, 2022 Revenues $443 $29 $— $472 Operating income 130 — 1 131 Net income 91 Nine Months Ended September 30, 2023 Revenues $1,192 $176 $2 $1,370 Operating income 340 23 — 363 Net income 267 Nine Months Ended September 30, 2022 Revenues $1,186 $194 $1 $1,381 Operating income 327 29 1 357 Net income 247
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 September 30, 2023 Revenues $995 $47 $13 $1,055 $22 $1,077 Operating income (loss) 319 (4) — 315 7 322 Net income (loss) attributable to Alliant Energy common shareowners 277 (18) 259 Three Months Ended September 30, 2022 Revenues $1,039 $62 $11 $1,112 $23 $1,135 Operating income (loss) 304 (3) 1 302 7 309 Net income (loss) attributable to Alliant Energy common shareowners 245 (18) 227 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Nine Months Ended September 30, 2023 Revenues $2,562 $400 $38 $3,000 $66 $3,066 Operating income 682 48 12 742 18 760 Net income (loss) attributable to Alliant Energy common shareowners 598 (16) 582 Nine Months Ended September 30, 2022 Revenues $2,624 $418 $35 $3,077 $70 $3,147 Operating income 680 62 4 746 23 769 Net income attributable to Alliant Energy common shareowners 574 5 579 IPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $551 $31 $12 $594 Operating income (loss) 171 (2) 4 173 Net income 170 Three Months Ended September 30, 2022 Revenues $596 $33 $11 $640 Operating income (loss) 174 (3) — 171 Net income 154 Nine Months Ended September 30, 2023 Revenues $1,370 $224 $36 $1,630 Operating income 342 25 12 379 Net income 331 Nine Months Ended September 30, 2022 Revenues $1,438 $224 $34 $1,696 Operating income 353 33 3 389 Net income 327 WPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $444 $16 $1 $461 Operating income (loss) 148 (2) (4) 142 Net income 107 Three Months Ended September 30, 2022 Revenues $443 $29 $— $472 Operating income 130 — 1 131 Net income 91 Nine Months Ended September 30, 2023 Revenues $1,192 $176 $2 $1,370 Operating income 340 23 — 363 Net income 267 Nine Months Ended September 30, 2022 Revenues $1,186 $194 $1 $1,381 Operating income 327 29 1 357 Net income 247
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 September 30, 2023 Revenues $995 $47 $13 $1,055 $22 $1,077 Operating income (loss) 319 (4) — 315 7 322 Net income (loss) attributable to Alliant Energy common shareowners 277 (18) 259 Three Months Ended September 30, 2022 Revenues $1,039 $62 $11 $1,112 $23 $1,135 Operating income (loss) 304 (3) 1 302 7 309 Net income (loss) attributable to Alliant Energy common shareowners 245 (18) 227 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Nine Months Ended September 30, 2023 Revenues $2,562 $400 $38 $3,000 $66 $3,066 Operating income 682 48 12 742 18 760 Net income (loss) attributable to Alliant Energy common shareowners 598 (16) 582 Nine Months Ended September 30, 2022 Revenues $2,624 $418 $35 $3,077 $70 $3,147 Operating income 680 62 4 746 23 769 Net income attributable to Alliant Energy common shareowners 574 5 579 IPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $551 $31 $12 $594 Operating income (loss) 171 (2) 4 173 Net income 170 Three Months Ended September 30, 2022 Revenues $596 $33 $11 $640 Operating income (loss) 174 (3) — 171 Net income 154 Nine Months Ended September 30, 2023 Revenues $1,370 $224 $36 $1,630 Operating income 342 25 12 379 Net income 331 Nine Months Ended September 30, 2022 Revenues $1,438 $224 $34 $1,696 Operating income 353 33 3 389 Net income 327 WPL Electric Gas Other Total (in millions) Three Months Ended September 30, 2023 Revenues $444 $16 $1 $461 Operating income (loss) 148 (2) (4) 142 Net income 107 Three Months Ended September 30, 2022 Revenues $443 $29 $— $472 Operating income 130 — 1 131 Net income 91 Nine Months Ended September 30, 2023 Revenues $1,192 $176 $2 $1,370 Operating income 340 23 — 363 Net income 267 Nine Months Ended September 30, 2022 Revenues $1,186 $194 $1 $1,381 Operating income 327 29 1 357 Net income 247

Related Parties (Tables)

Related Parties (Tables)	9 Months Ended
	Sep. 30, 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 and nine months ended September 30 were as follows (in millions): IPL WPL Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $46 $45 $134 $136 $40 $39 $120 $117 Sales credited 3 11 11 11 23 31 45 62 Purchases billed 133 119 320 342 5 42 21 103
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL September 30, 2023 December 31, 2022 September 30, 2023 December 31, 2022 Net payables to Corporate Services $136 $103 $71 $56
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 ATC billings to WPL $41 $38 $119 $107 WPL billings to ATC 5 6 16 14
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 and nine months ended September 30 were as follows (in millions): IPL WPL Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $46 $45 $134 $136 $40 $39 $120 $117 Sales credited 3 11 11 11 23 31 45 62 Purchases billed 133 119 320 342 5 42 21 103
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL September 30, 2023 December 31, 2022 September 30, 2023 December 31, 2022 Net payables to Corporate Services $136 $103 $71 $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 and nine months ended September 30 were as follows (in millions): IPL WPL Three Months Nine Months Three Months Nine Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $46 $45 $134 $136 $40 $39 $120 $117 Sales credited 3 11 11 11 23 31 45 62 Purchases billed 133 119 320 342 5 42 21 103
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL September 30, 2023 December 31, 2022 September 30, 2023 December 31, 2022 Net payables to Corporate Services $136 $103 $71 $56
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions): Three Months Nine Months 2023 2022 2023 2022 ATC billings to WPL $41 $38 $119 $107 WPL billings to ATC 5 6 16 14

Summary Of Significant Accoun_3

Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 189	$ 10
Money market fund investments weighted-average interest rate, percentage	5%
IPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 180	$ 10
Money market fund investments weighted-average interest rate, percentage	5%
WPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Money market fund investments	$ 9
Money market fund investments weighted-average interest rate, percentage	5%

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Regulatory Matters [Line Items]
Regulatory assets	$ 2,269	$ 2,046
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	1,590	1,386
WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	679	660
Assets retired early [Member]
Regulatory Matters [Line Items]
Regulatory assets	282	70
Assets retired early [Member] | IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	267	53
Assets retired early [Member] | WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	15	$ 17
Assets retired early [Member] | Lansing Generating Station
Regulatory Matters [Line Items]
Regulatory assets	221
Assets retired early [Member] | Lansing Generating Station | IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	$ 221

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory assets	$ 2,269	$ 2,046
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	919	929
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	371	392
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	282	70
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	199	151
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	138	160
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	72	84
IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	66
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	46	48
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	194	146
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,590	1,386
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	825	848
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	187	197
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	267	53
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	155	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	11	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	27	48
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	66
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	70	63
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	679	660
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	94	81
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	184	195
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	15	17
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	44	41
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	127	159
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	45	36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	46	48
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 124	$ 83

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,187	$ 1,324
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	569	579
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	397	398
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	91	210
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	41	40
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	9	32
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	6	20
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	74	45
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	655	754
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	301	303
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	249	259
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	52	115
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	11	38
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	6	10
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	36	29
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	532	570
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	268	276
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	148	139
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	39	95
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	30	2
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	9	32
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	0	10
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 38	$ 16

Property, Plant and Equipment (

Property, Plant and Equipment (Narrative) (Details)	Sep. 30, 2023
WPL [Member] | West Riverside Energy Center [Member]
Property, Plant and Equipment [Line Items]
Ownership interest, percent	73.80%

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) - Receivables Sold [Member] - IPL [Member] - USD ($) $ in Millions	Dec. 31, 2023	Oct. 31, 2023	Sep. 30, 2023
Receivables [Line Items]
Available capacity			$ 109
Subsequent Event [Member]
Receivables [Line Items]
Available capacity	$ 110	$ 5
Financial Asset, Past Due [Member]
Receivables [Line Items]
Outstanding receivables past due			$ 18

Receivables (Gross Write-offs F

Receivables (Gross Write-offs For Accounts Receivable) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Gross write-offs for accounts receivable, originated in 2022	$ 3	$ 11
Gross write-offs for accounts receivable, originated in 2023	6	8
IPL [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross write-offs for accounts receivable, originated in 2022	2	7
Gross write-offs for accounts receivable, originated in 2023	4	5
WPL [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Gross write-offs for accounts receivable, originated in 2022	1	4
Gross write-offs for accounts receivable, originated in 2023	$ 2	$ 3

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Maximum [Member]
Receivables [Line Items]
Maximum outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 94	$ 36	$ 110	$ 66
Average [Member]
Receivables [Line Items]
Average outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 46	$ 3	$ 68	$ 8

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Receivables [Line Items]
Fair value of deferred proceeds	$ 236	$ 185
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	236	185
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	161	145
Unbilled utility revenues	88	132
Other receivables	1	0
Receivables sold to third party	250	277
Less: cash proceeds	1	80
Deferred proceeds	249	197
Less: allowance for expected credit losses	13	12
Fair value of deferred proceeds	$ 236	$ 185

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Receivables [Line Items]
Collections	$ 616	$ 670	$ 1,720	$ 1,731
Write-offs, net of recoveries	$ 5	$ 3	$ 9	$ 6

Investments (Unconsolidated Equ

Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (14)	$ (5)	$ (45)	$ (37)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(12)	(7)	(37)	(29)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(2)	2	(8)	(8)
Total [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (14)	$ (5)	$ (45)	$ (37)

Common Equity (Narrative) (Deta

Common Equity (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023
Common Equity [Line Items]
Proceeds from issuance of common stock, net	$ 125	$ 6	$ 201	$ 19
At The Market Offering Program [Member]
Common Equity [Line Items]
Common stock issued during period, At-the-market offering program (in shares)			3,569,937
Proceeds from issuance of common stock, net			$ 183
Fees and commissions from issuance of common stock			$ 2
At The Market Offering Program [Member] | Forecast [Member]
Common Equity [Line Items]
Maximum aggregate gross sales price of common stock that can be offered and sold					$ 225

Common Equity (Common Share Act

Common Equity (Common Share Activity) (Details)	9 Months Ended
	Sep. 30, 2023 shares
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1, 2023 (in shares)	251,134,966
Shareowner Direct Plan (in shares)	339,850
Equity-based compensation plans (in shares)	134,334
Shares outstanding, September 30, 2023 (in shares)	255,179,087
At The Market Offering Program [Member]
Common Stock Oustanding [Roll Forward]
Common stock issued during period, At-the-market offering program (in shares)	3,569,937

Common Equity (Changes in Share

Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			$ 6,276
Beginning balance	$ 6,452	$ 6,166	6,276	$ 5,990
Net income attributable to common shareowners	259	227	582	579
Net income			582	579
Common stock dividends	(115)	(106)	(341)	(322)
At-the-market offering program and Shareowner Direct Plan issuances	125	6	201	19
Equity-based compensation plans and other	4	1	4	(1)
Other comprehensive income, net of tax	1		4
Contributions from noncontrolling interest			0	29
Distributions to noncontrolling interest		(29)	0	(29)
Ending balance	6,726		6,726
Ending balance	$ 6,726	$ 6,265	$ 6,726	$ 6,265
Common stock dividends (in dollars per share)	$ 0.4525	$ 0.4275	$ 1.3575	$ 1.2825
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 3	$ 3	$ 3	$ 3
Ending balance	3	3	3	3
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,854	2,759	2,777	2,749
At-the-market offering program and Shareowner Direct Plan issuances	125	6	201	19
Equity-based compensation plans and other	3	2	4	(1)
Ending balance	2,982	2,767	2,982	2,767
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,606	3,387	3,509	3,250
Net income attributable to common shareowners	259	227	582	579
Common stock dividends	(115)	(106)	(341)	(322)
Equity-based compensation plans and other				1
Ending balance	3,750	3,508	3,750	3,508
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3	0	0	0
Other comprehensive income, net of tax	1		4
Ending balance	4	0	4	0
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(14)	(12)	(13)	(12)
Equity-based compensation plans and other	1	(1)		(1)
Ending balance	(13)	(13)	(13)	(13)
Noncontrolling Interest [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	29	0	0
Contributions from noncontrolling interest				29
Distributions to noncontrolling interest		(29)		(29)
Ending balance	0	0	0	0
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,808
Beginning balance	3,869	3,782	3,808	3,769
Net income	170	154	331	327
Common stock dividends	(70)	(80)	(210)	(240)
Capital contributions from parent	20		60	0
Ending balance	3,989		3,989
Ending balance	3,989	3,856	3,989	3,856
IPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	33	33	33	33
Ending balance	33	33	33	33
IPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,847	2,807	2,807	2,807
Capital contributions from parent	20		60
Ending balance	2,867	2,807	2,867	2,807
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	989	942	968	929
Net income	170	154	331	327
Common stock dividends	(70)	(80)	(210)	(240)
Ending balance	1,089	1,016	1,089	1,016
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,491
Beginning balance	3,739	3,183	3,491	2,823
Net income	107	91	267	247
Common stock dividends	(46)	(44)	(138)	(133)
Equity-based compensation plans and other				(1)
Capital contributions from parent	65	155	245	420
Contributions from noncontrolling interest			0	29
Distributions to noncontrolling interest		(29)	0	(29)
Ending balance	3,865		3,865
Ending balance	3,865	3,356	3,865	3,356
WPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	66	66	66	66
Ending balance	66	66	66	66
WPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,413	1,968	2,233	1,704
Equity-based compensation plans and other				(1)
Capital contributions from parent	65	155	245	420
Ending balance	2,478	2,123	2,478	2,123
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,260	1,120	1,192	1,053
Net income	107	91	267	247
Common stock dividends	(46)	(44)	(138)	(133)
Ending balance	1,321	1,167	1,321	1,167
WPL [Member] | Noncontrolling Interest [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	29	0	0
Contributions from noncontrolling interest				29
Distributions to noncontrolling interest		(29)		(29)
Ending balance	$ 0	$ 0	$ 0	$ 0

Debt (Narrative) (Details)

Debt (Narrative) (Details)	9 Months Ended
	Sep. 30, 2023 USD ($) Integer $ / shares shares	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Debt [Line Items]
Line of credit facility, current borrowing capacity	$ 1,000,000,000
Payments to retire long-term debt	404,000,000	$ 379,000,000
Long-term debt, fair value	7,863,000,000		$ 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	3,422,000,000		3,228,000,000
WPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	300,000,000
Long-term debt, fair value	2,722,000,000		$ 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
Senior Debentures [Member] | 5.70% senior debenture, due 2033 | IPL [Member]
Debt [Line Items]
Long-term debt	$ 300,000,000
Interest rate, percent	5.70%
Senior Notes [Member] | 3.75% senior notes, due 2023 [Member] | Alliant Energy Finance LLC [Member]
Debt [Line Items]
Payments to retire long-term debt	$ 400,000,000
Interest rate, percent	3.75%
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	$ 567,000,000
Unamortized debt issuance costs	8,000,000
Long-term debt, fair value	$ 556,000,000
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	Sep. 30, 2023 USD ($)
Debt [Line Items]
Amount outstanding	$ 451
Weighted average interest rates	5.50%
Available credit facility capacity	$ 549
IPL [Member]
Debt [Line Items]
Amount outstanding	$ 0
Weighted average interest rates	0%
Available credit facility capacity	$ 250
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 120
Weighted average interest rates	5.40%
Available credit facility capacity	$ 180

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 474	$ 449	$ 793	$ 577
Average amount outstanding (based on daily outstanding balances)	$ 440	$ 353	$ 367	$ 377
Weighted average interest rates	5.50%	2.40%	5.10%	1.20%
IPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 7	$ 0	$ 70	$ 0
Average amount outstanding (based on daily outstanding balances)	$ 0	$ 0	$ 2	$ 0
Weighted average interest rates	5.50%	0%	5.30%	0%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 125	$ 251	$ 349	$ 252
Average amount outstanding (based on daily outstanding balances)	$ 86	$ 110	$ 135	$ 160
Weighted average interest rates	5.40%	2%	4.90%	0.90%

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,077	$ 1,135	$ 3,066	$ 3,147
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	995	1,039	2,562	2,624
Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	374	376	943	956
Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	241	243	627	628
Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	280	289	740	743
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	59	68	154	168
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	41	63	98	129
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47	62	400	418
Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	28	233	237
Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	18	122	127
Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	4	12	15
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	12	33	39
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	11	38	35
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	9	32	29
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	6	6
Non-utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	23	66	70
Non-utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	23	66	70
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	594	640	1,630	1,696
IPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	551	596	1,370	1,438
IPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	209	222	503	529
IPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	158	165	399	411
IPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	153	172	389	418
IPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	21	19	47	49
IPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	18	32	31
IPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	31	33	224	224
IPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	14	131	127
IPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	8	65	62
IPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	3	8	10
IPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	8	20	25
IPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	11	36	34
IPL [Member] | Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	9	32	29
IPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	2	4	5
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	461	472	1,370	1,381
WPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	444	443	1,192	1,186
WPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	165	154	440	427
WPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	83	78	228	217
WPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	127	117	351	325
WPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	38	49	107	119
WPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	31	45	66	98
WPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16	29	176	194
WPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	14	102	110
WPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	10	57	65
WPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	4	5
WPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	4	13	14
WPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	0	2	1
WPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1	$ 0	$ 2	$ 1

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2024	Dec. 31, 2023
Income Taxes [Line Items]
Regulatory assets			$ (40)	$ 102
Income tax expense (benefit)	$ 5	$ 14	3	26
Tax-related [Member]
Income Taxes [Line Items]
Regulatory assets	73
Income tax expense (benefit)	8	8
Forecast [Member]
Income Taxes [Line Items]
State income tax rate, percent					7.10%	8.40%
IPL [Member]
Income Taxes [Line Items]
Regulatory assets			(55)	(18)
Income tax expense (benefit)	(31)	(16)	(55)	(39)
IPL [Member] | Tax-related [Member]
Income Taxes [Line Items]
Regulatory assets	73
WPL [Member]
Income Taxes [Line Items]
Regulatory assets			16	120
Income tax expense (benefit)	$ 21	$ 16	$ 47	$ 50

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Effective Tax Rate [Line Items]
Overall income tax rate	2%	6%	1%	4%
IPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	(22.00%)	(12.00%)	(20.00%)	(14.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	16%	15%	15%	17%

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Sep. 30, 2023 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 431
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	737
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	6
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	520
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 208

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($) shares
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 11
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	$ 6
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 5
Omnibus Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Shares included in diluted earnings per share (in shares) | shares	274,960

Benefit Plans (Defined Benefit

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 3	$ 4	$ 7
Interest cost	12	9	35	27
Expected return on plan assets	(14)	(18)	(40)	(52)
Amortization of prior service credit	(1)	0	(1)	0
Amortization of actuarial loss	7	8	21	24
Total	6	2	19	6
OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	0	2	2
Interest cost	3	1	7	4
Expected return on plan assets	(2)	0	(4)	(3)
Amortization of prior service credit	0	0	0	0
Amortization of actuarial loss	0	1	1	2
Total	2	2	6	5
IPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	2	4
Interest cost	6	4	16	12
Expected return on plan assets	(6)	(7)	(19)	(23)
Amortization of actuarial loss	2	3	8	10
Total	2	1	7	3
IPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	1
Interest cost	1	1	3	2
Expected return on plan assets	(1)	(1)	(3)	(3)
Amortization of actuarial loss	0	0	1	0
Total	0	0	1	0
WPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	1	2
Interest cost	5	4	15	12
Expected return on plan assets	(5)	(7)	(16)	(23)
Amortization of actuarial loss	3	4	10	12
Total	3	1	10	3
WPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	0	1	0
Interest cost	1	1	3	2
Expected return on plan assets	(1)	0	(1)	0
Amortization of actuarial loss	0	0	0	1
Total	$ 1	$ 1	$ 3	$ 3

Benefit Plans (Recognized Compe

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Compensation expense	$ 4	$ 3	$ 10	$ 9
Income tax benefits	1	1	3	3
IPL [Member]
Compensation expense	2	2	5	5
Income tax benefits	1	0	1	1
WPL [Member]
Compensation expense	2	1	4	4
Income tax benefits	$ 0	$ 0	$ 1	$ 1

Benefit Plans (Summary Of Equit

Benefit Plans (Summary Of Equity-based Compensation Plans Grants) (Details)	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	108,513
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	123,990
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 52.71
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	105,982
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 52.77

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Derivative Instruments [Line Items]
Non-current interest rate swap liabilities	$ 544		$ 544		$ 518
Accumulated other comprehensive income, interest rate swap	4		4		$ 0
Interest expense, interest rate swap	99	$ 83	289	$ 235
Alliant Energy Finance LLC [Member] | Interest Rate Swap [Member] | Term Loan Credit Agreement [Member]
Derivative Instruments [Line Items]
Interest rate swap	$ 300		$ 300
Interest rate swap, fixed interest rate percentage	3.93%		3.93%
Non-current interest rate swap liabilities	$ 6		$ 6
Accumulated other comprehensive income, interest rate swap	4		4
Interest expense, interest rate swap	$ 1		$ 2

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member]	9 Months Ended
	Sep. 30, 2023 Dekatherms MWh T
Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	1,661
Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	746
Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	915
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	18,122
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	8,078
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	10,044
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	180,519
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	85,457
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	95,062
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	370
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	217
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	153

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 67	$ 111
Non-current derivative assets	62	126
Current derivative liabilities	32	59
Non-current derivative liabilities	34	20
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	51	69
Non-current derivative assets	34	69
Current derivative liabilities	15	40
Non-current derivative liabilities	6	6
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	16	42
Non-current derivative assets	28	57
Current derivative liabilities	17	19
Non-current derivative liabilities	$ 28	$ 14

Derivative Instruments (Balance

Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	$ 129	$ 237
Derivative assets, Net	108	193
Derivative liabilities, Gross (as reported)	66	79
Derivative liabilities, Net	45	35
IPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	85	138
Derivative assets, Net	73	108
Derivative liabilities, Gross (as reported)	21	46
Derivative liabilities, Net	9	16
WPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	44	99
Derivative assets, Net	35	85
Derivative liabilities, Gross (as reported)	45	33
Derivative liabilities, Net	$ 36	$ 19

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets:
Money market fund investments	$ 189	$ 10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	7,863	7,339
IPL [Member]
Assets:
Money market fund investments	180	10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	3,422	3,228
WPL [Member]
Assets:
Money market fund investments	9
Liabilities:
Long-term debt (incl. current maturities)	2,722	2,542
Commodity Contracts [Member]
Assets:
Derivatives	129	237
Liabilities:
Derivatives	66	79
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	85	138
Liabilities:
Derivatives	21	46
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	44	99
Liabilities:
Derivatives	45	33
Interest Rate Swap [Member]
Assets:
Derivatives	6	0
Level 1 [Member]
Assets:
Money market fund investments	189	10
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	180	10
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 1 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	0
Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	7,863	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)	3,422	3,228
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,722	2,542
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	80	206
Liabilities:
Derivatives	60	67
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	45	111
Liabilities:
Derivatives	16	35
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	35	95
Liabilities:
Derivatives	44	32
Level 2 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	6	0
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	0	1
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	49	31
Liabilities:
Derivatives	6	12
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	40	27
Liabilities:
Derivatives	5	11
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	9	4
Liabilities:
Derivatives	1	1
Level 3 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	0
Carrying Amount [Member]
Assets:
Money market fund investments	189	10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	8,838	8,076
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	180	10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	3,944	3,646
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	3,069	2,770
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	129	237
Liabilities:
Derivatives	66	79
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	85	138
Liabilities:
Derivatives	21	46
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	44	99
Liabilities:
Derivatives	45	33
Carrying Amount [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	$ 6	$ 0

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 54	$ 72	$ 19	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	17	(1)	6	(17)
Purchases			62	79
Sales	(1)	0	(2)	0
Settlements	(27)	(26)	(42)	(46)
Ending balance	43	45	43	45
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 September 30	17	(1)	6	(17)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	41	58	16	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	12	(6)	0	(13)
Purchases			51	58
Sales	(1)	0	(2)	0
Settlements	(17)	(19)	(30)	(30)
Ending balance	35	33	35	33
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 September 30	12	(6)	0	(14)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	13	14	3	11
Total net gains (losses) included in changes in net assets (realized/unrealized)	5	5	6	(4)
Purchases			11	21
Settlements	(10)	(7)	(12)	(16)
Ending balance	8	12	8	12
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 September 30	5	5	6	(3)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	175	244	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases			0	0
Sales	0	0	0	0
Settlements	61	4	51	34
Ending balance	236	248	236	248
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 September 30	0	0	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	175	244	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases			0	0
Sales	0	0	0	0
Settlements	61	4	51	34
Ending balance	236	248	236	248
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 September 30	$ 0	$ 0	$ 0	$ 0

Fair Value Measurements (Fair_3

Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 43	$ 54	$ 19	$ 45	$ 72	$ 29
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3
Fair value, net derivative liabilities			(10)
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	40		29
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	35	41	16	33	58	18
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	4
Fair value, net derivative liabilities			(9)
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	31		25
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	8	$ 13	3	$ 12	$ 14	$ 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	(1)		(1)
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 9		$ 4

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2021	Dec. 31, 2020
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,275
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	596
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	631
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	221
Capital Purchase Commitment [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	175
Capital Purchase Commitment [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	46
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	51
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	9 Months Ended
	Sep. 30, 2023 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,275
Individual commitments incurred	1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	596
Individual commitments incurred	1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	631
Individual commitments incurred	1
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	962
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	436
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	526
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	188
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	108
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	80
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	125
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	52
Other [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 25

Commitments And Contingencies_4

Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	9 Months Ended
	Sep. 30, 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	9
Minimum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	5
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	36
Maximum [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Range of estimated future costs	11
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		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 1,077	$ 1,135	$ 3,066	$ 3,147
Operating income (loss)	322	309	760	769
Net income (loss) attributable to common shareowners	259	227	582	579
Net income			582	579
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	594	640	1,630	1,696
Operating income (loss)	173	171	379	389
Net income	170	154	331	327
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	461	472	1,370	1,381
Operating income (loss)	142	131	363	357
Net income	107	91	267	247
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	995	1,039	2,562	2,624
Operating income (loss)	319	304	682	680
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	551	596	1,370	1,438
Operating income (loss)	171	174	342	353
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	444	443	1,192	1,186
Operating income (loss)	148	130	340	327
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	47	62	400	418
Operating income (loss)	(4)	(3)	48	62
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	31	33	224	224
Operating income (loss)	(2)	(3)	25	33
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	16	29	176	194
Operating income (loss)	(2)	0	23	29
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	13	11	38	35
Operating income (loss)	0	1	12	4
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	12	11	36	34
Operating income (loss)	4	0	12	3
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1	0	2	1
Operating income (loss)	(4)	1	0	1
Non-utility and Other [Member]
Segment Reporting Information [Line Items]
Revenues	22	23	66	70
Operating income (loss)	7	7	18	23
Net income (loss) attributable to common shareowners	(18)	(18)	(16)	5
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	1,055	1,112	3,000	3,077
Operating income (loss)	315	302	742	746
Net income (loss) attributable to common shareowners	$ 277	$ 245	$ 598	$ 574

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 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		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Corporate Services Billings [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 46	$ 45	$ 134	$ 136
Corporate Services Billings [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	40	39	120	117
Sales Credited [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	3	11	11	11
Sales Credited [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	23	31	45	62
Purchases Billed [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	133	119	320	342
Purchases Billed [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 5	$ 42	$ 21	$ 103

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Related Party [Member] - Corporate Services [Member] - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 136	$ 103
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 71	$ 56

Related Parties (Amounts Billed

Related Parties (Amounts Billed Between Parties) (Details) - ATC LLC [Member] - WPL [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
ATC Billings To WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 41	$ 38	$ 119	$ 107
WPL Billings To ATC [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 5	$ 6	$ 16	$ 14