Alliant Energy (LNT) 10-Q 4 Aug 23 2023 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	6 Months Ended
	Jun. 30, 2023 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 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	252,719,092
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues:
Electric utility	$ 799	$ 812	$ 1,567	$ 1,586
Gas utility	77	94	353	356
Other utility	13	13	25	23
Non-utility	23	24	45	47
Total revenues	912	943	1,990	2,012
Operating expenses:
Electric production fuel and purchased power	166	191	322	359
Electric transmission service	138	133	284	271
Cost of gas sold	33	48	215	216
Other operation and maintenance	163	166	338	320
Depreciation and amortization	167	166	333	332
Taxes other than income taxes	28	27	59	54
Total operating expenses	695	731	1,551	1,552
Operating income	217	212	439	460
Other (income) and deductions:
Interest expense	96	78	190	152
Equity income from unconsolidated investments, net	(14)	(16)	(31)	(32)
Allowance for funds used during construction	(24)	(13)	(43)	(24)
Other	(1)	0	2	1
Total other (income) and deductions	57	49	118	97
Income before income taxes	160	163	321	363
Income tax expense (benefit)	0	4	(2)	12
Net income			323	351
Net income attributable to common shareowners	$ 160	$ 159	$ 323	$ 351
Weighted average number of common shares outstanding:
Basic (in shares)	251,700	250,900	251,400	250,700
Diluted (in shares)	251,900	251,100	251,600	251,000
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 0.64	$ 0.63	$ 1.28	$ 1.40
Diluted (in dollars per share)	$ 0.64	$ 0.63	$ 1.28	$ 1.40
IPL [Member]
Revenues:
Electric utility	$ 431	$ 442	$ 819	$ 843
Gas utility	44	52	194	191
Other utility	12	12	24	22
Total revenues	487	506	1,037	1,056
Operating expenses:
Electric production fuel and purchased power	66	83	113	150
Electric transmission service	96	91	201	188
Cost of gas sold	20	27	116	112
Other operation and maintenance	85	87	181	171
Depreciation and amortization	96	95	191	189
Taxes other than income taxes	14	14	29	28
Total operating expenses	377	397	831	838
Operating income	110	109	206	218
Other (income) and deductions:
Interest expense	37	37	74	74
Allowance for funds used during construction	(4)	(3)	(8)	(5)
Other	1	0	3	(1)
Total other (income) and deductions	34	34	69	68
Income before income taxes	76	75	137	150
Income tax expense (benefit)	(13)	(12)	(24)	(23)
Net income	89	87	161	173
WPL [Member]
Revenues:
Electric utility	368	370	748	743
Gas utility	33	42	159	165
Other utility	1	1	1	1
Total revenues	402	413	908	909
Operating expenses:
Electric production fuel and purchased power	99	108	209	209
Electric transmission service	42	41	83	83
Cost of gas sold	13	21	99	104
Other operation and maintenance	67	67	133	123
Depreciation and amortization	69	69	137	139
Taxes other than income taxes	13	12	27	24
Total operating expenses	303	318	688	682
Operating income	99	95	220	227
Other (income) and deductions:
Interest expense	36	28	72	55
Allowance for funds used during construction	(19)	(10)	(35)	(18)
Other	(4)	0	(3)	0
Total other (income) and deductions	13	18	34	37
Income before income taxes	86	77	186	190
Income tax expense (benefit)	14	14	26	34
Net income	$ 72	$ 63	$ 160	$ 156

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 13	$ 20
Accounts receivable, less allowance for expected credit losses	428	516
Production fuel, at weighted average cost	64	53
Gas stored underground, at weighted average cost	69	132
Materials and supplies, at weighted average cost	172	140
Regulatory assets	196	166
Other	196	223
Total current assets	1,138	1,250
Property, plant and equipment, net	16,306	16,247
Investments:
ATC Holdings	372	358
Other	212	201
Total investments	584	559
Other assets:
Regulatory assets	2,148	1,880
Deferred charges and other	207	227
Total other assets	2,355	2,107
Total assets	20,383	20,163
Current liabilities:
Current maturities of long-term debt	409	408
Commercial paper	391	642
Other short-term borrowings	50	0
Accounts payable	585	756
Regulatory liabilities	121	206
Other	337	351
Total current liabilities	1,893	2,363
Long-term debt, net (excluding current portion)	8,186	7,668
Other liabilities:
Deferred tax liabilities	1,969	1,943
Regulatory liabilities	1,087	1,118
Pension and other benefit obligations	262	277
Other	534	518
Total other liabilities	3,852	3,856
Commitments and contingencies (Note 13)
Common equity:
Common stock	3	3
Additional paid-in capital	2,854	2,777
Retained earnings	3,606	3,509
Accumulated other comprehensive income	3	0
Shares in deferred compensation trust - 405,051 and 402,134 shares at a weighted average cost of $33.69 and $32.63 per share	(14)	(13)
Total common equity	6,452	6,276
Total liabilities and equity	20,383	20,163
IPL [Member]
Current assets:
Cash and cash equivalents	9	15
Accounts receivable, less allowance for expected credit losses	204	259
Production fuel, at weighted average cost	31	23
Gas stored underground, at weighted average cost	27	60
Materials and supplies, at weighted average cost	100	83
Regulatory assets	90	85
Other	78	93
Total current assets	539	618
Property, plant and equipment, net	7,923	8,046
Other assets:
Regulatory assets	1,558	1,301
Deferred charges and other	101	110
Total other assets	1,659	1,411
Total assets	10,121	10,075
Current liabilities:
Accounts payable	247	239
Accounts payable to associated companies	40	28
Accrued taxes	51	52
Accrued interest	35	35
Regulatory liabilities	73	114
Other	97	113
Total current liabilities	543	581
Long-term debt, net (excluding current portion)	3,702	3,646
Other liabilities:
Deferred tax liabilities	1,061	1,047
Regulatory liabilities	603	640
Pension and other benefit obligations	60	62
Other	283	291
Total other liabilities	2,007	2,040
Commitments and contingencies (Note 13)
Common equity:
Common stock	33	33
Additional paid-in capital	2,847	2,807
Retained earnings	989	968
Total common equity	3,869	3,808
Total liabilities and equity	10,121	10,075
WPL [Member]
Current assets:
Cash and cash equivalents	3	5
Accounts receivable, less allowance for expected credit losses	210	244
Production fuel, at weighted average cost	33	29
Gas stored underground, at weighted average cost	42	73
Materials and supplies, at weighted average cost	70	54
Regulatory assets	106	81
Prepaid gross receipts tax	47	42
Other	47	60
Total current assets	558	588
Property, plant and equipment, net	7,882	7,722
Other assets:
Regulatory assets	590	579
Deferred charges and other	69	98
Total other assets	659	677
Total assets	9,099	8,987
Current liabilities:
Commercial paper	44	290
Accounts payable	277	456
Regulatory liabilities	48	92
Other	140	111
Total current liabilities	509	949
Long-term debt, net (excluding current portion)	3,068	2,770
Other liabilities:
Deferred tax liabilities	785	789
Regulatory liabilities	484	478
Pension and other benefit obligations	127	140
Other	387	370
Total other liabilities	1,783	1,777
Commitments and contingencies (Note 13)
Common equity:
Common stock	66	66
Additional paid-in capital	2,413	2,233
Retained earnings	1,260	1,192
Total common equity	3,739	3,491
Total liabilities and equity	$ 9,099	$ 8,987

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 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)	252,719,092	251,134,966
Shares in deferred compensation trust (in shares)	405,051	402,134
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 33.69	$ 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	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net income	$ 323	$ 351
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	333	332
Equity component of allowance for funds used during construction	(32)	(18)
Other	14	14
Other changes in assets and liabilities:
Accounts receivable	(186)	(283)
Gas stored underground	63	17
Derivative assets	86	(183)
Regulatory assets	(36)	(116)
Accounts payable	(84)	95
Derivative liabilities	18	86
Regulatory liabilities	(116)	74
Deferred income taxes	24	34
Other	(96)	(103)
Net cash flows from operating activities	311	300
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(758)	(550)
Other construction and acquisition expenditures	(62)	(43)
Cash receipts on sold receivables	272	233
Proceeds from sales of partial ownership interest in West Riverside	120	0
Other	(54)	(10)
Net cash flows from (used for) investing activities	(482)	(370)
Cash flows from (used for) financing activities:
Common stock dividends	(226)	(215)
Proceeds from issuance of common stock, net	76	13
Proceeds from issuance of long-term debt	862	650
Payments to retire long-term debt	(404)	(304)
Net change in commercial paper and other short-term borrowings	(146)	(116)
Contributions from noncontrolling interest	0	29
Other	(1)	(7)
Net cash flows from (used for) financing activities	161	50
Net increase (decrease) in cash, cash equivalents and restricted cash	(10)	(20)
Cash, cash equivalents and restricted cash at beginning of period	24	40
Cash, cash equivalents and restricted cash at end of period	14	20
Supplemental cash flows information:
Interest	(179)	(146)
Income taxes, net	3	(4)
Significant non-cash investing and financing activities:
Accrued capital expenditures	300	200
Beneficial interest obtained in exchange for securitized accounts receivable	175	244
IPL [Member]
Cash flows from operating activities:
Net income	161	173
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	191	189
Other	2	(9)
Other changes in assets and liabilities:
Accounts receivable	(216)	(256)
Gas stored underground	33	12
Derivative assets	43	(123)
Regulatory assets	(2)	(52)
Accounts payable	(32)	67
Derivative liabilities	(9)	63
Regulatory liabilities	(78)	53
Deferred income taxes	8	24
Other	(49)	(58)
Net cash flows from operating activities	52	83
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(251)	(172)
Cash receipts on sold receivables	272	233
Other	(36)	(1)
Net cash flows from (used for) investing activities	(15)	60
Cash flows from (used for) financing activities:
Common stock dividends	(140)	(160)
Capital contributions from parent	40	0
Net change in commercial paper and other short-term borrowings	55	0
Other	2	(4)
Net cash flows from (used for) financing activities	(43)	(164)
Net increase (decrease) in cash, cash equivalents and restricted cash	(6)	(21)
Cash, cash equivalents and restricted cash at beginning of period	15	34
Cash, cash equivalents and restricted cash at end of period	9	13
Supplemental cash flows information:
Interest	(74)	(74)
Income taxes, net	25	19
Significant non-cash investing and financing activities:
Accrued capital expenditures	95	45
Beneficial interest obtained in exchange for securitized accounts receivable	175	244
WPL [Member]
Cash flows from operating activities:
Net income	160	156
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	137	139
Equity component of allowance for funds used during construction	(26)	(14)
Other	(4)	18
Other changes in assets and liabilities:
Accounts receivable	33	(17)
Gas stored underground	31	5
Derivative assets	47	(60)
Regulatory assets	(35)	(65)
Accounts payable	(54)	38
Derivative liabilities	27	23
Regulatory liabilities	(38)	20
Other	(10)	(45)
Net cash flows from operating activities	268	198
Cash flows from (used for) investing activities:
Utility business construction and acquisition expenditures	(507)	(378)
Proceeds from sales of partial ownership interest in West Riverside	120	0
Other	(15)	(6)
Net cash flows from (used for) investing activities	(402)	(384)
Cash flows from (used for) financing activities:
Common stock dividends	(92)	(89)
Capital contributions from parent	180	265
Proceeds from issuance of long-term debt	297	0
Net change in commercial paper and other short-term borrowings	(246)	(14)
Contributions from noncontrolling interest	0	29
Other	(7)	(3)
Net cash flows from (used for) financing activities	132	188
Net increase (decrease) in cash, cash equivalents and restricted cash	(2)	2
Cash, cash equivalents and restricted cash at beginning of period	5	2
Cash, cash equivalents and restricted cash at end of period	3	4
Supplemental cash flows information:
Interest	(69)	(54)
Income taxes, net	(42)	(31)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 196	$ 150

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 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 six months ended June 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.
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 six months ended June 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.
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 six months ended June 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.

Regulatory Matters

Regulatory Matters	6 Months Ended
	Jun. 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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $957 $929 $868 $848 $89 $81 Pension and OPEB costs 378 392 190 197 188 195 Assets retired early 290 70 274 53 16 17 Asset retirement obligations 197 151 156 110 41 41 Commodity cost recovery 145 160 6 1 139 159 Derivatives 102 84 41 48 61 36 IPL’s Duane Arnold Energy Center PPA amendment 54 66 54 66 — — WPL’s Western Wisconsin gas distribution expansion investments 47 48 — — 47 48 Other 174 146 59 63 115 83 $2,344 $2,046 $1,648 $1,386 $696 $660 Assets retired early - 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 on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of June 30, 2023 was $226 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. Continued recovery of the remaining net book value of Lansing is expected to be addressed in future IPL rate reviews. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the six months ended June 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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $572 $579 $301 $303 $271 $276 Cost of removal obligations 405 398 260 259 145 139 Derivatives 90 210 48 115 42 95 Commodity cost recovery 39 40 15 38 24 2 Electric transmission cost recovery 19 20 14 10 5 10 WPL’s West Riverside liquidated damages 17 32 — — 17 32 Other 66 45 38 29 28 16 $1,208 $1,324 $676 $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 six months ended June 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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $957 $929 $868 $848 $89 $81 Pension and OPEB costs 378 392 190 197 188 195 Assets retired early 290 70 274 53 16 17 Asset retirement obligations 197 151 156 110 41 41 Commodity cost recovery 145 160 6 1 139 159 Derivatives 102 84 41 48 61 36 IPL’s Duane Arnold Energy Center PPA amendment 54 66 54 66 — — WPL’s Western Wisconsin gas distribution expansion investments 47 48 — — 47 48 Other 174 146 59 63 115 83 $2,344 $2,046 $1,648 $1,386 $696 $660 Assets retired early - 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 on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of June 30, 2023 was $226 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. Continued recovery of the remaining net book value of Lansing is expected to be addressed in future IPL rate reviews. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the six months ended June 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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $572 $579 $301 $303 $271 $276 Cost of removal obligations 405 398 260 259 145 139 Derivatives 90 210 48 115 42 95 Commodity cost recovery 39 40 15 38 24 2 Electric transmission cost recovery 19 20 14 10 5 10 WPL’s West Riverside liquidated damages 17 32 — — 17 32 Other 66 45 38 29 28 16 $1,208 $1,324 $676 $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 six months ended June 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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $957 $929 $868 $848 $89 $81 Pension and OPEB costs 378 392 190 197 188 195 Assets retired early 290 70 274 53 16 17 Asset retirement obligations 197 151 156 110 41 41 Commodity cost recovery 145 160 6 1 139 159 Derivatives 102 84 41 48 61 36 IPL’s Duane Arnold Energy Center PPA amendment 54 66 54 66 — — WPL’s Western Wisconsin gas distribution expansion investments 47 48 — — 47 48 Other 174 146 59 63 115 83 $2,344 $2,046 $1,648 $1,386 $696 $660 Assets retired early - 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 on Alliant Energy’s and IPL’s balance sheets. The related regulatory asset balance as of June 30, 2023 was $226 million, which is currently included in IPL’s rate base and IPL is earning a return of and a return on the remaining balance. Continued recovery of the remaining net book value of Lansing is expected to be addressed in future IPL rate reviews. Derivatives - Refer to Note 11 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the six months ended June 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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $572 $579 $301 $303 $271 $276 Cost of removal obligations 405 398 260 259 145 139 Derivatives 90 210 48 115 42 95 Commodity cost recovery 39 40 15 38 24 2 Electric transmission cost recovery 19 20 14 10 5 10 WPL’s West Riverside liquidated damages 17 32 — — 17 32 Other 66 45 38 29 28 16 $1,208 $1,324 $676 $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 six months ended June 30, 2023.

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 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 six months ended June 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 six months ended June 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 six months ended June 30, 2023. As a result of these transactions, WPL’s undivided current ownership interest in West Riverside is 73.8%.

Receivables

Receivables	6 Months Ended
	Jun. 30, 2023
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three and six months ended June 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 Six Months Three Months Six Months Alliant Energy $3 $8 $2 $2 IPL 2 5 1 1 WPL 1 3 1 1 NOTE 4(b) - Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. In March 2023, IPL amended and extended through March 2024 the purchase commitment from the third party to which it sells its receivables. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of June 30, 2023, IPL had $50 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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $110 $66 $110 $66 Average outstanding aggregate cash proceeds 101 18 79 11 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2023 December 31, 2022 Customer accounts receivable $148 $145 Unbilled utility revenues 100 132 Receivables sold to third party 248 277 Less: cash proceeds 60 80 Deferred proceeds 188 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $175 $185 As of June 30, 2023, outstanding receivables past due under the Receivables Agreement were $20 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Collections $514 $500 $1,104 $1,061 Write-offs, net of recoveries 2 1 4 3
IPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three and six months ended June 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 Six Months Three Months Six Months Alliant Energy $3 $8 $2 $2 IPL 2 5 1 1 WPL 1 3 1 1 NOTE 4(b) - Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. In March 2023, IPL amended and extended through March 2024 the purchase commitment from the third party to which it sells its receivables. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of June 30, 2023, IPL had $50 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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $110 $66 $110 $66 Average outstanding aggregate cash proceeds 101 18 79 11 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2023 December 31, 2022 Customer accounts receivable $148 $145 Unbilled utility revenues 100 132 Receivables sold to third party 248 277 Less: cash proceeds 60 80 Deferred proceeds 188 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $175 $185 As of June 30, 2023, outstanding receivables past due under the Receivables Agreement were $20 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Collections $514 $500 $1,104 $1,061 Write-offs, net of recoveries 2 1 4 3
WPL [Member]
Receivables [Line Items]
Receivables	RECEIVABLES NOTE 4(a) - Accounts Receivable - For the three and six months ended June 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 Six Months Three Months Six Months Alliant Energy $3 $8 $2 $2 IPL 2 5 1 1 WPL 1 3 1 1

Investments

Investments	6 Months Ended
	Jun. 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 six months ended June 30 was as follows (in millions): Three Months Six Months 2023 2022 2023 2022 ATC Holdings ($12) ($11) ($25) ($23) Other (2) (5) (6) (9) ($14) ($16) ($31) ($32)

Common Equity

Common Equity	6 Months Ended
	Jun. 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 1,221,775 Shareowner Direct Plan 228,017 Equity-based compensation plans 134,334 Shares outstanding, June 30, 2023 252,719,092 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 June 30, 2023, Alliant Energy issued 1,221,775 shares of common stock through this program and received cash proceeds of $64 million, net of $1 million in commissions and fees. Alliant Energy also had commitments not recognized on its balance sheet at June 30, 2023 to sell 172,701 shares of common stock under sales transactions executed through this program in late June 2023. Subsequent to June 30, 2023, Alliant Energy issued shares to settle these transactions in exchange for net cash proceeds of $9 million. 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 (Loss) Trust Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $— $6,328 Net income attributable to Alliant Energy common shareowners 160 160 Common stock dividends ($0.4525 per share) (113) (113) At-the-market offering program and Shareowner Direct Plan issuances 70 70 Equity-based compensation plans and other 4 (1) 3 Other comprehensive income, net of tax 4 4 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Net income attributable to Alliant Energy common shareowners 159 159 Common stock dividends ($0.4275 per share) (108) (108) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 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 (Loss) Trust Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 323 323 Common stock dividends ($0.905 per share) (226) (226) At-the-market offering program and Shareowner Direct Plan issuances 76 76 Equity-based compensation plans and other 1 (1) — Other comprehensive income, net of tax 3 3 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 351 351 Common stock dividends ($0.855 per share) (215) (215) Shareowner Direct Plan issuances 13 13 Equity-based compensation plans and other (3) 1 (2) Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $33 $2,807 $970 $3,810 Net income 89 89 Common stock dividends (70) (70) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $33 $2,807 $935 $3,775 Net income 87 87 Common stock dividends (80) (80) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 161 161 Common stock dividends (140) (140) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 173 173 Common stock dividends (160) (160) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $66 $2,413 $1,234 $— $3,713 Net income 72 72 Common stock dividends (46) (46) Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $66 $1,884 $1,101 $— $3,051 Net income 63 63 Common stock dividends (44) (44) Capital contributions from parent 85 85 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 160 160 Common stock dividends (92) (92) Capital contributions from parent 180 180 Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 156 156 Common stock dividends (89) (89) Capital contributions from parent 265 265 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183
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 1,221,775 Shareowner Direct Plan 228,017 Equity-based compensation plans 134,334 Shares outstanding, June 30, 2023 252,719,092 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 June 30, 2023, Alliant Energy issued 1,221,775 shares of common stock through this program and received cash proceeds of $64 million, net of $1 million in commissions and fees. Alliant Energy also had commitments not recognized on its balance sheet at June 30, 2023 to sell 172,701 shares of common stock under sales transactions executed through this program in late June 2023. Subsequent to June 30, 2023, Alliant Energy issued shares to settle these transactions in exchange for net cash proceeds of $9 million. 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 (Loss) Trust Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $— $6,328 Net income attributable to Alliant Energy common shareowners 160 160 Common stock dividends ($0.4525 per share) (113) (113) At-the-market offering program and Shareowner Direct Plan issuances 70 70 Equity-based compensation plans and other 4 (1) 3 Other comprehensive income, net of tax 4 4 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Net income attributable to Alliant Energy common shareowners 159 159 Common stock dividends ($0.4275 per share) (108) (108) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 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 (Loss) Trust Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 323 323 Common stock dividends ($0.905 per share) (226) (226) At-the-market offering program and Shareowner Direct Plan issuances 76 76 Equity-based compensation plans and other 1 (1) — Other comprehensive income, net of tax 3 3 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 351 351 Common stock dividends ($0.855 per share) (215) (215) Shareowner Direct Plan issuances 13 13 Equity-based compensation plans and other (3) 1 (2) Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $33 $2,807 $970 $3,810 Net income 89 89 Common stock dividends (70) (70) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $33 $2,807 $935 $3,775 Net income 87 87 Common stock dividends (80) (80) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 161 161 Common stock dividends (140) (140) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 173 173 Common stock dividends (160) (160) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $66 $2,413 $1,234 $— $3,713 Net income 72 72 Common stock dividends (46) (46) Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $66 $1,884 $1,101 $— $3,051 Net income 63 63 Common stock dividends (44) (44) Capital contributions from parent 85 85 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 160 160 Common stock dividends (92) (92) Capital contributions from parent 180 180 Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 156 156 Common stock dividends (89) (89) Capital contributions from parent 265 265 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183
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 1,221,775 Shareowner Direct Plan 228,017 Equity-based compensation plans 134,334 Shares outstanding, June 30, 2023 252,719,092 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 June 30, 2023, Alliant Energy issued 1,221,775 shares of common stock through this program and received cash proceeds of $64 million, net of $1 million in commissions and fees. Alliant Energy also had commitments not recognized on its balance sheet at June 30, 2023 to sell 172,701 shares of common stock under sales transactions executed through this program in late June 2023. Subsequent to June 30, 2023, Alliant Energy issued shares to settle these transactions in exchange for net cash proceeds of $9 million. 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 (Loss) Trust Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $— $6,328 Net income attributable to Alliant Energy common shareowners 160 160 Common stock dividends ($0.4525 per share) (113) (113) At-the-market offering program and Shareowner Direct Plan issuances 70 70 Equity-based compensation plans and other 4 (1) 3 Other comprehensive income, net of tax 4 4 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Net income attributable to Alliant Energy common shareowners 159 159 Common stock dividends ($0.4275 per share) (108) (108) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 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 (Loss) Trust Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 323 323 Common stock dividends ($0.905 per share) (226) (226) At-the-market offering program and Shareowner Direct Plan issuances 76 76 Equity-based compensation plans and other 1 (1) — Other comprehensive income, net of tax 3 3 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 351 351 Common stock dividends ($0.855 per share) (215) (215) Shareowner Direct Plan issuances 13 13 Equity-based compensation plans and other (3) 1 (2) Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $33 $2,807 $970 $3,810 Net income 89 89 Common stock dividends (70) (70) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $33 $2,807 $935 $3,775 Net income 87 87 Common stock dividends (80) (80) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 161 161 Common stock dividends (140) (140) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 173 173 Common stock dividends (160) (160) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $66 $2,413 $1,234 $— $3,713 Net income 72 72 Common stock dividends (46) (46) Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $66 $1,884 $1,101 $— $3,051 Net income 63 63 Common stock dividends (44) (44) Capital contributions from parent 85 85 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 160 160 Common stock dividends (92) (92) Capital contributions from parent 180 180 Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 156 156 Common stock dividends (89) (89) Capital contributions from parent 265 265 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183

Debt

Debt	6 Months Ended
	Jun. 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): June 30, 2023 Alliant Energy IPL WPL Amount outstanding $391 $— $44 Weighted average interest rates 5.3% —% 5.2% Available credit facility capacity (a) $554 $195 $256 Alliant Energy IPL WPL Three Months Ended June 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $391 $441 $70 $— $91 $222 Average amount outstanding (based on daily outstanding balances) $88 $337 $6 $— $18 $166 Weighted average interest rates 5.3% 1.0% 5.3% —% 5.2% 0.9% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $330 $390 $3 $— $160 $185 Weighted average interest rates 4.8% 0.6% 5.3% —% 4.8% 0.5% (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2023. 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 June 30, 2023. NOTE 7(b) Long-term Debt - 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 will be allocated or disbursed for the development and acquisition of its solar EGUs. As of June 30, 2023, $55 million of commercial paper was recorded in “Long-term debt, net” on Alliant Energy’s and IPL’s balance sheets due to the existence of the long-term single credit facility that back-stops this commercial paper balance, along with Alliant Energy’s and IPL’s intent and ability to refinance these balances on a long-term basis. As of June 30, 2023, this commercial paper balance had a 5% interest rate. 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 June 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 June 30, 2023, the net carrying amount of the Notes was $566 million, with unamortized debt issuance costs of $9 million, and the estimated fair value (Level 2) of the Notes was $573 million. As of June 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): June 30, 2023 Alliant Energy IPL WPL Amount outstanding $391 $— $44 Weighted average interest rates 5.3% —% 5.2% Available credit facility capacity (a) $554 $195 $256 Alliant Energy IPL WPL Three Months Ended June 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $391 $441 $70 $— $91 $222 Average amount outstanding (based on daily outstanding balances) $88 $337 $6 $— $18 $166 Weighted average interest rates 5.3% 1.0% 5.3% —% 5.2% 0.9% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $330 $390 $3 $— $160 $185 Weighted average interest rates 4.8% 0.6% 5.3% —% 4.8% 0.5% (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2023. 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 June 30, 2023. NOTE 7(b) Long-term Debt - 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 will be allocated or disbursed for the development and acquisition of its solar EGUs. As of June 30, 2023, $55 million of commercial paper was recorded in “Long-term debt, net” on Alliant Energy’s and IPL’s balance sheets due to the existence of the long-term single credit facility that back-stops this commercial paper balance, along with Alliant Energy’s and IPL’s intent and ability to refinance these balances on a long-term basis. As of June 30, 2023, this commercial paper balance had a 5% interest rate.
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): June 30, 2023 Alliant Energy IPL WPL Amount outstanding $391 $— $44 Weighted average interest rates 5.3% —% 5.2% Available credit facility capacity (a) $554 $195 $256 Alliant Energy IPL WPL Three Months Ended June 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $391 $441 $70 $— $91 $222 Average amount outstanding (based on daily outstanding balances) $88 $337 $6 $— $18 $166 Weighted average interest rates 5.3% 1.0% 5.3% —% 5.2% 0.9% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $330 $390 $3 $— $160 $185 Weighted average interest rates 4.8% 0.6% 5.3% —% 4.8% 0.5% (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2023. 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 June 30, 2023. NOTE 7(b) Long-term Debt - 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 will be allocated or disbursed for the development and acquisition of its solar EGUs.

Revenues

Revenues	6 Months Ended
	Jun. 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 June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $284 $289 $151 $158 $133 $131 Retail - commercial 201 196 129 127 72 69 Retail - industrial 245 244 130 136 115 108 Wholesale 49 54 14 16 35 38 Bulk power and other 20 29 7 5 13 24 Total Electric Utility 799 812 431 442 368 370 Gas Utility: Retail - residential 42 51 24 28 18 23 Retail - commercial 22 27 12 14 10 13 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 13 6 8 4 5 Total Gas Utility 77 94 44 52 33 42 Other Utility: Steam 11 11 11 11 — — Other utility 2 2 1 1 1 1 Total Other Utility 13 13 12 12 1 1 Non-Utility and Other: Travero and other 23 24 — — — — Total Non-Utility and Other 23 24 — — — — Total revenues $912 $943 $487 $506 $402 $413 Alliant Energy IPL WPL Six Months Ended June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $569 $581 $294 $308 $275 $273 Retail - commercial 385 386 241 246 144 140 Retail - industrial 460 453 236 246 224 207 Wholesale 95 101 26 31 69 70 Bulk power and other 58 65 22 12 36 53 Total Electric Utility 1,567 1,586 819 843 748 743 Gas Utility: Retail - residential 210 210 117 113 93 97 Retail - commercial 110 109 56 54 54 55 Retail - industrial 9 11 6 7 3 4 Transportation/other 24 26 15 17 9 9 Total Gas Utility 353 356 194 191 159 165 Other Utility: Steam 22 20 22 20 — — Other utility 3 3 2 2 1 1 Total Other Utility 25 23 24 22 1 1 Non-Utility and Other: Travero and other 45 47 — — — — Total Non-Utility and Other 45 47 — — — — Total revenues $1,990 $2,012 $1,037 $1,056 $908 $909
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 June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $284 $289 $151 $158 $133 $131 Retail - commercial 201 196 129 127 72 69 Retail - industrial 245 244 130 136 115 108 Wholesale 49 54 14 16 35 38 Bulk power and other 20 29 7 5 13 24 Total Electric Utility 799 812 431 442 368 370 Gas Utility: Retail - residential 42 51 24 28 18 23 Retail - commercial 22 27 12 14 10 13 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 13 6 8 4 5 Total Gas Utility 77 94 44 52 33 42 Other Utility: Steam 11 11 11 11 — — Other utility 2 2 1 1 1 1 Total Other Utility 13 13 12 12 1 1 Non-Utility and Other: Travero and other 23 24 — — — — Total Non-Utility and Other 23 24 — — — — Total revenues $912 $943 $487 $506 $402 $413 Alliant Energy IPL WPL Six Months Ended June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $569 $581 $294 $308 $275 $273 Retail - commercial 385 386 241 246 144 140 Retail - industrial 460 453 236 246 224 207 Wholesale 95 101 26 31 69 70 Bulk power and other 58 65 22 12 36 53 Total Electric Utility 1,567 1,586 819 843 748 743 Gas Utility: Retail - residential 210 210 117 113 93 97 Retail - commercial 110 109 56 54 54 55 Retail - industrial 9 11 6 7 3 4 Transportation/other 24 26 15 17 9 9 Total Gas Utility 353 356 194 191 159 165 Other Utility: Steam 22 20 22 20 — — Other utility 3 3 2 2 1 1 Total Other Utility 25 23 24 22 1 1 Non-Utility and Other: Travero and other 45 47 — — — — Total Non-Utility and Other 45 47 — — — — Total revenues $1,990 $2,012 $1,037 $1,056 $908 $909
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 June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $284 $289 $151 $158 $133 $131 Retail - commercial 201 196 129 127 72 69 Retail - industrial 245 244 130 136 115 108 Wholesale 49 54 14 16 35 38 Bulk power and other 20 29 7 5 13 24 Total Electric Utility 799 812 431 442 368 370 Gas Utility: Retail - residential 42 51 24 28 18 23 Retail - commercial 22 27 12 14 10 13 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 13 6 8 4 5 Total Gas Utility 77 94 44 52 33 42 Other Utility: Steam 11 11 11 11 — — Other utility 2 2 1 1 1 1 Total Other Utility 13 13 12 12 1 1 Non-Utility and Other: Travero and other 23 24 — — — — Total Non-Utility and Other 23 24 — — — — Total revenues $912 $943 $487 $506 $402 $413 Alliant Energy IPL WPL Six Months Ended June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $569 $581 $294 $308 $275 $273 Retail - commercial 385 386 241 246 144 140 Retail - industrial 460 453 236 246 224 207 Wholesale 95 101 26 31 69 70 Bulk power and other 58 65 22 12 36 53 Total Electric Utility 1,567 1,586 819 843 748 743 Gas Utility: Retail - residential 210 210 117 113 93 97 Retail - commercial 110 109 56 54 54 55 Retail - industrial 9 11 6 7 3 4 Transportation/other 24 26 15 17 9 9 Total Gas Utility 353 356 194 191 159 165 Other Utility: Steam 22 20 22 20 — — Other utility 3 3 2 2 1 1 Total Other Utility 25 23 24 22 1 1 Non-Utility and Other: Travero and other 45 47 — — — — Total Non-Utility and Other 45 47 — — — — Total revenues $1,990 $2,012 $1,037 $1,056 $908 $909

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2023
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate —% 2% (1%) 3% (17%) (16%) (18%) (15%) 16% 18% 14% 18% Deferred Tax Assets and Liabilities - Carryforwards - At June 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 $503 $8 $1 Federal tax credits 2030-2043 708 485 214
IPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate —% 2% (1%) 3% (17%) (16%) (18%) (15%) 16% 18% 14% 18% Deferred Tax Assets and Liabilities - Carryforwards - At June 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 $503 $8 $1 Federal tax credits 2030-2043 708 485 214
WPL [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES Income Tax Rates - Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate —% 2% (1%) 3% (17%) (16%) (18%) (15%) 16% 18% 14% 18% Deferred Tax Assets and Liabilities - Carryforwards - At June 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 $503 $8 $1 Federal tax credits 2030-2043 708 485 214

Benefit Plans

Benefit Plans	6 Months Ended
	Jun. 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 six months ended June 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 Six Months Three Months Six Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $2 $2 $4 $— $1 $1 $2 Interest cost 12 9 23 18 2 2 4 3 Expected return on plan assets (13) (17) (26) (34) (1) (2) (2) (3) Amortization of actuarial loss 7 8 14 16 1 — 1 1 $7 $2 $13 $4 $2 $1 $4 $3 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $2 $3 $— $1 $— $1 Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (13) (16) (1) (1) (2) (2) Amortization of actuarial loss 3 4 6 7 1 — 1 — $3 $1 $5 $2 $1 $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $1 $2 $— $— $— $— Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (11) (16) — — — — Amortization of actuarial loss 4 4 7 8 — 1 — 1 $4 $1 $7 $2 $1 $1 $2 $2 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 six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $3 $3 $6 $7 $2 $1 $3 $4 $1 $1 $2 $3 Income tax benefits 1 1 2 2 — — 1 1 — — 1 1 As of June 30, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $15 million, $8 million and $6 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the six months ended June 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 106,927 $55.68 Performance restricted stock units 122,178 52.77 Restricted stock units 104,849 52.81 As of June 30, 2023, 206,177 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 six months ended June 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 Six Months Three Months Six Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $2 $2 $4 $— $1 $1 $2 Interest cost 12 9 23 18 2 2 4 3 Expected return on plan assets (13) (17) (26) (34) (1) (2) (2) (3) Amortization of actuarial loss 7 8 14 16 1 — 1 1 $7 $2 $13 $4 $2 $1 $4 $3 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $2 $3 $— $1 $— $1 Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (13) (16) (1) (1) (2) (2) Amortization of actuarial loss 3 4 6 7 1 — 1 — $3 $1 $5 $2 $1 $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $1 $2 $— $— $— $— Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (11) (16) — — — — Amortization of actuarial loss 4 4 7 8 — 1 — 1 $4 $1 $7 $2 $1 $1 $2 $2 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 six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $3 $3 $6 $7 $2 $1 $3 $4 $1 $1 $2 $3 Income tax benefits 1 1 2 2 — — 1 1 — — 1 1 As of June 30, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $15 million, $8 million and $6 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the six months ended June 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 106,927 $55.68 Performance restricted stock units 122,178 52.77 Restricted stock units 104,849 52.81 As of June 30, 2023, 206,177 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 six months ended June 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 Six Months Three Months Six Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $2 $2 $4 $— $1 $1 $2 Interest cost 12 9 23 18 2 2 4 3 Expected return on plan assets (13) (17) (26) (34) (1) (2) (2) (3) Amortization of actuarial loss 7 8 14 16 1 — 1 1 $7 $2 $13 $4 $2 $1 $4 $3 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $2 $3 $— $1 $— $1 Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (13) (16) (1) (1) (2) (2) Amortization of actuarial loss 3 4 6 7 1 — 1 — $3 $1 $5 $2 $1 $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $1 $2 $— $— $— $— Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (11) (16) — — — — Amortization of actuarial loss 4 4 7 8 — 1 — 1 $4 $1 $7 $2 $1 $1 $2 $2 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 six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $3 $3 $6 $7 $2 $1 $3 $4 $1 $1 $2 $3 Income tax benefits 1 1 2 2 — — 1 1 — — 1 1 As of June 30, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $15 million, $8 million and $6 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the six months ended June 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 106,927 $55.68 Performance restricted stock units 122,178 52.77 Restricted stock units 104,849 52.81 As of June 30, 2023, 206,177 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2023
Derivative Instruments [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - As of June 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 1,171 2023-2025 24,874 2023-2024 192,421 2023-2032 466 2023 IPL 537 2023-2025 10,163 2023-2024 92,087 2023-2030 224 2023 WPL 634 2023-2025 14,711 2023-2024 100,334 2023-2032 242 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 June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $86 $111 $61 $69 $25 $42 Non-current derivative assets 61 126 34 69 27 57 Current derivative liabilities 54 59 27 40 27 19 Non-current derivative liabilities 43 20 10 6 33 14 During the six months ended June 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 pr ices, partially offset by new FTRs resulting from the annual FTR auction in the second quarter of 2023 operated by MISO. Alliant Energy’s and WPL’s derivative liabilities increased primarily due to lower natural gas prices. 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 June 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 differe nt 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 June 30, 2023 Derivative assets $147 $114 $95 $73 $52 $41 Derivative liabilities 97 64 37 15 60 49 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 June 30, 2023, $4 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 June 30, 2023, accumulated other comprehensive income included $3 million of income related to the interest rate swap. For the three and six months ended June 30, 2023, $1 million and $1 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 June 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 1,171 2023-2025 24,874 2023-2024 192,421 2023-2032 466 2023 IPL 537 2023-2025 10,163 2023-2024 92,087 2023-2030 224 2023 WPL 634 2023-2025 14,711 2023-2024 100,334 2023-2032 242 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 June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $86 $111 $61 $69 $25 $42 Non-current derivative assets 61 126 34 69 27 57 Current derivative liabilities 54 59 27 40 27 19 Non-current derivative liabilities 43 20 10 6 33 14 During the six months ended June 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 pr ices, partially offset by new FTRs resulting from the annual FTR auction in the second quarter of 2023 operated by MISO. Alliant Energy’s and WPL’s derivative liabilities increased primarily due to lower natural gas prices. 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 June 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 differe nt 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 June 30, 2023 Derivative assets $147 $114 $95 $73 $52 $41 Derivative liabilities 97 64 37 15 60 49 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 June 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 1,171 2023-2025 24,874 2023-2024 192,421 2023-2032 466 2023 IPL 537 2023-2025 10,163 2023-2024 92,087 2023-2030 224 2023 WPL 634 2023-2025 14,711 2023-2024 100,334 2023-2032 242 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 June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $86 $111 $61 $69 $25 $42 Non-current derivative assets 61 126 34 69 27 57 Current derivative liabilities 54 59 27 40 27 19 Non-current derivative liabilities 43 20 10 6 33 14 During the six months ended June 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 pr ices, partially offset by new FTRs resulting from the annual FTR auction in the second quarter of 2023 operated by MISO. Alliant Energy’s and WPL’s derivative liabilities increased primarily due to lower natural gas prices. 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 June 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 differe nt 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 June 30, 2023 Derivative assets $147 $114 $95 $73 $52 $41 Derivative liabilities 97 64 37 15 60 49 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	6 Months Ended
	Jun. 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 June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 147 — 80 67 147 237 — 206 31 237 Interest rate derivatives 4 — 4 — 4 — — — — — Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 97 — 84 13 97 79 — 67 12 79 Long-term debt (incl. current maturities) 8,595 — 7,950 1 7,951 8,076 — 7,338 1 7,339 IPL June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 95 — 44 51 95 138 — 111 27 138 Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 37 — 27 10 37 46 — 35 11 46 Long-term debt 3,702 — 3,321 — 3,321 3,646 — 3,228 — 3,228 WPL June 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 $52 $— $36 $16 $52 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 60 — 57 3 60 33 — 32 1 33 Long-term debt 3,068 — 2,875 — 2,875 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 June 30 2023 2022 2023 2022 Beginning balance, April 1 ($5) $10 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (7) (10) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) 5 (7) 22 17 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($7) ($10) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (11) (16) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) (15) (20) (10) 30 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($11) ($16) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2023 2022 2023 2022 Beginning balance, April 1 $— $7 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (13) (3) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) 4 (4) 22 17 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($13) ($3) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (12) (7) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) (13) (11) (10) 30 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($12) ($8) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2023 2022 Beginning balance, April 1 ($5) $3 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (7) Purchases 11 21 Settlements 1 (3) Ending balance, June 30 $13 $14 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 June 30 $6 ($7) WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (9) Purchases 11 21 Settlements (2) (9) Ending balance, June 30 $13 $14 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 June 30 $1 ($8) (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 June 30, 2023 ($8) $62 ($5) $46 ($3) $16 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 June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 147 — 80 67 147 237 — 206 31 237 Interest rate derivatives 4 — 4 — 4 — — — — — Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 97 — 84 13 97 79 — 67 12 79 Long-term debt (incl. current maturities) 8,595 — 7,950 1 7,951 8,076 — 7,338 1 7,339 IPL June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 95 — 44 51 95 138 — 111 27 138 Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 37 — 27 10 37 46 — 35 11 46 Long-term debt 3,702 — 3,321 — 3,321 3,646 — 3,228 — 3,228 WPL June 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 $52 $— $36 $16 $52 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 60 — 57 3 60 33 — 32 1 33 Long-term debt 3,068 — 2,875 — 2,875 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 June 30 2023 2022 2023 2022 Beginning balance, April 1 ($5) $10 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (7) (10) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) 5 (7) 22 17 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($7) ($10) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (11) (16) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) (15) (20) (10) 30 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($11) ($16) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2023 2022 2023 2022 Beginning balance, April 1 $— $7 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (13) (3) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) 4 (4) 22 17 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($13) ($3) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (12) (7) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) (13) (11) (10) 30 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($12) ($8) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2023 2022 Beginning balance, April 1 ($5) $3 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (7) Purchases 11 21 Settlements 1 (3) Ending balance, June 30 $13 $14 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 June 30 $6 ($7) WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (9) Purchases 11 21 Settlements (2) (9) Ending balance, June 30 $13 $14 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 June 30 $1 ($8) (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 June 30, 2023 ($8) $62 ($5) $46 ($3) $16 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 June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 147 — 80 67 147 237 — 206 31 237 Interest rate derivatives 4 — 4 — 4 — — — — — Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 97 — 84 13 97 79 — 67 12 79 Long-term debt (incl. current maturities) 8,595 — 7,950 1 7,951 8,076 — 7,338 1 7,339 IPL June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 95 — 44 51 95 138 — 111 27 138 Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 37 — 27 10 37 46 — 35 11 46 Long-term debt 3,702 — 3,321 — 3,321 3,646 — 3,228 — 3,228 WPL June 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 $52 $— $36 $16 $52 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 60 — 57 3 60 33 — 32 1 33 Long-term debt 3,068 — 2,875 — 2,875 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 June 30 2023 2022 2023 2022 Beginning balance, April 1 ($5) $10 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (7) (10) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) 5 (7) 22 17 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($7) ($10) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (11) (16) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) (15) (20) (10) 30 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($11) ($16) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2023 2022 2023 2022 Beginning balance, April 1 $— $7 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (13) (3) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) 4 (4) 22 17 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($13) ($3) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (12) (7) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) (13) (11) (10) 30 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($12) ($8) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2023 2022 Beginning balance, April 1 ($5) $3 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (7) Purchases 11 21 Settlements 1 (3) Ending balance, June 30 $13 $14 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 June 30 $6 ($7) WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (9) Purchases 11 21 Settlements (2) (9) Ending balance, June 30 $13 $14 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 June 30 $1 ($8) (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 June 30, 2023 ($8) $62 ($5) $46 ($3) $16 December 31, 2022 (10) 29 (9) 25 (1) 4

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 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 June 30, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $188 million, $87 million and $101 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 June 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,083 $494 $589 Coal 163 79 84 Other (a) 106 51 25 $1,352 $624 $698 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 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 June 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 June 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 $59 million as of June 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 June 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 June 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 June 30, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $188 million, $87 million and $101 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 June 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,083 $494 $589 Coal 163 79 84 Other (a) 106 51 25 $1,352 $624 $698 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 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 June 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 June 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 $59 million as of June 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 June 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 June 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 June 30, 2023, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $188 million, $87 million and $101 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 June 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,083 $494 $589 Coal 163 79 84 Other (a) 106 51 25 $1,352 $624 $698 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 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 June 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 June 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 $59 million as of June 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 June 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 June 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	6 Months Ended
	Jun. 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 June 30, 2023 Revenues $799 $77 $13 $889 $23 $912 Operating income 200 2 7 209 8 217 Net income (loss) attributable to Alliant Energy common shareowners 161 (1) 160 Three Months Ended June 30, 2022 Revenues $812 $94 $13 $919 $24 $943 Operating income 195 8 1 204 8 212 Net income attributable to Alliant Energy common shareowners 150 9 159 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2023 Revenues $1,567 $353 $25 $1,945 $45 $1,990 Operating income 363 52 11 426 13 439 Net income attributable to Alliant Energy common shareowners 321 2 323 Six Months Ended June 30, 2022 Revenues $1,586 $356 $23 $1,965 $47 $2,012 Operating income 376 65 4 445 15 460 Net income attributable to Alliant Energy common shareowners 329 22 351 IPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $431 $44 $12 $487 Operating income 105 — 5 110 Net income 89 Three Months Ended June 30, 2022 Revenues $442 $52 $12 $506 Operating income 104 4 1 109 Net income 87 Six Months Ended June 30, 2023 Revenues $819 $194 $24 $1,037 Operating income 171 27 8 206 Net income 161 Six Months Ended June 30, 2022 Revenues $843 $191 $22 $1,056 Operating income 179 36 3 218 Net income 173 WPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $368 $33 $1 $402 Operating income 95 2 2 99 Net income 72 Three Months Ended June 30, 2022 Revenues $370 $42 $1 $413 Operating income 91 4 — 95 Net income 63 Six Months Ended June 30, 2023 Revenues $748 $159 $1 $908 Operating income 192 25 3 220 Net income 160 Six Months Ended June 30, 2022 Revenues $743 $165 $1 $909 Operating income 197 29 1 227 Net income 156
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 June 30, 2023 Revenues $799 $77 $13 $889 $23 $912 Operating income 200 2 7 209 8 217 Net income (loss) attributable to Alliant Energy common shareowners 161 (1) 160 Three Months Ended June 30, 2022 Revenues $812 $94 $13 $919 $24 $943 Operating income 195 8 1 204 8 212 Net income attributable to Alliant Energy common shareowners 150 9 159 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2023 Revenues $1,567 $353 $25 $1,945 $45 $1,990 Operating income 363 52 11 426 13 439 Net income attributable to Alliant Energy common shareowners 321 2 323 Six Months Ended June 30, 2022 Revenues $1,586 $356 $23 $1,965 $47 $2,012 Operating income 376 65 4 445 15 460 Net income attributable to Alliant Energy common shareowners 329 22 351 IPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $431 $44 $12 $487 Operating income 105 — 5 110 Net income 89 Three Months Ended June 30, 2022 Revenues $442 $52 $12 $506 Operating income 104 4 1 109 Net income 87 Six Months Ended June 30, 2023 Revenues $819 $194 $24 $1,037 Operating income 171 27 8 206 Net income 161 Six Months Ended June 30, 2022 Revenues $843 $191 $22 $1,056 Operating income 179 36 3 218 Net income 173 WPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $368 $33 $1 $402 Operating income 95 2 2 99 Net income 72 Three Months Ended June 30, 2022 Revenues $370 $42 $1 $413 Operating income 91 4 — 95 Net income 63 Six Months Ended June 30, 2023 Revenues $748 $159 $1 $908 Operating income 192 25 3 220 Net income 160 Six Months Ended June 30, 2022 Revenues $743 $165 $1 $909 Operating income 197 29 1 227 Net income 156
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 June 30, 2023 Revenues $799 $77 $13 $889 $23 $912 Operating income 200 2 7 209 8 217 Net income (loss) attributable to Alliant Energy common shareowners 161 (1) 160 Three Months Ended June 30, 2022 Revenues $812 $94 $13 $919 $24 $943 Operating income 195 8 1 204 8 212 Net income attributable to Alliant Energy common shareowners 150 9 159 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2023 Revenues $1,567 $353 $25 $1,945 $45 $1,990 Operating income 363 52 11 426 13 439 Net income attributable to Alliant Energy common shareowners 321 2 323 Six Months Ended June 30, 2022 Revenues $1,586 $356 $23 $1,965 $47 $2,012 Operating income 376 65 4 445 15 460 Net income attributable to Alliant Energy common shareowners 329 22 351 IPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $431 $44 $12 $487 Operating income 105 — 5 110 Net income 89 Three Months Ended June 30, 2022 Revenues $442 $52 $12 $506 Operating income 104 4 1 109 Net income 87 Six Months Ended June 30, 2023 Revenues $819 $194 $24 $1,037 Operating income 171 27 8 206 Net income 161 Six Months Ended June 30, 2022 Revenues $843 $191 $22 $1,056 Operating income 179 36 3 218 Net income 173 WPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $368 $33 $1 $402 Operating income 95 2 2 99 Net income 72 Three Months Ended June 30, 2022 Revenues $370 $42 $1 $413 Operating income 91 4 — 95 Net income 63 Six Months Ended June 30, 2023 Revenues $748 $159 $1 $908 Operating income 192 25 3 220 Net income 160 Six Months Ended June 30, 2022 Revenues $743 $165 $1 $909 Operating income 197 29 1 227 Net income 156

Related Parties

Related Parties	6 Months Ended
	Jun. 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 six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $48 $51 $88 $91 $43 $42 $80 $78 Sales credited 1 — 8 — 10 13 22 31 Purchases billed 94 129 187 223 2 39 17 61 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2023 December 31, 2022 June 30, 2023 December 31, 2022 Net payables to Corporate Services $116 $103 $73 $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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 ATC billings to WPL $44 $35 $78 $69 WPL billings to ATC 5 5 11 8 WPL owed ATC net amounts of $10 million as of June 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 six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $48 $51 $88 $91 $43 $42 $80 $78 Sales credited 1 — 8 — 10 13 22 31 Purchases billed 94 129 187 223 2 39 17 61 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2023 December 31, 2022 June 30, 2023 December 31, 2022 Net payables to Corporate Services $116 $103 $73 $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 six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $48 $51 $88 $91 $43 $42 $80 $78 Sales credited 1 — 8 — 10 13 22 31 Purchases billed 94 129 187 223 2 39 17 61 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2023 December 31, 2022 June 30, 2023 December 31, 2022 Net payables to Corporate Services $116 $103 $73 $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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 ATC billings to WPL $44 $35 $78 $69 WPL billings to ATC 5 5 11 8 WPL owed ATC net amounts of $10 million as of June 30, 2023 and $10 million as of December 31, 2022.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Pay vs Performance Disclosure
Net income	$ 323	$ 351

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Jun. 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)	6 Months Ended
	Jun. 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.
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.
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.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2023
Regulatory Assets [Line Items]
Regulatory Assets	Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $957 $929 $868 $848 $89 $81 Pension and OPEB costs 378 392 190 197 188 195 Assets retired early 290 70 274 53 16 17 Asset retirement obligations 197 151 156 110 41 41 Commodity cost recovery 145 160 6 1 139 159 Derivatives 102 84 41 48 61 36 IPL’s Duane Arnold Energy Center PPA amendment 54 66 54 66 — — WPL’s Western Wisconsin gas distribution expansion investments 47 48 — — 47 48 Other 174 146 59 63 115 83 $2,344 $2,046 $1,648 $1,386 $696 $660
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $572 $579 $301 $303 $271 $276 Cost of removal obligations 405 398 260 259 145 139 Derivatives 90 210 48 115 42 95 Commodity cost recovery 39 40 15 38 24 2 Electric transmission cost recovery 19 20 14 10 5 10 WPL’s West Riverside liquidated damages 17 32 — — 17 32 Other 66 45 38 29 28 16 $1,208 $1,324 $676 $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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $957 $929 $868 $848 $89 $81 Pension and OPEB costs 378 392 190 197 188 195 Assets retired early 290 70 274 53 16 17 Asset retirement obligations 197 151 156 110 41 41 Commodity cost recovery 145 160 6 1 139 159 Derivatives 102 84 41 48 61 36 IPL’s Duane Arnold Energy Center PPA amendment 54 66 54 66 — — WPL’s Western Wisconsin gas distribution expansion investments 47 48 — — 47 48 Other 174 146 59 63 115 83 $2,344 $2,046 $1,648 $1,386 $696 $660
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $572 $579 $301 $303 $271 $276 Cost of removal obligations 405 398 260 259 145 139 Derivatives 90 210 48 115 42 95 Commodity cost recovery 39 40 15 38 24 2 Electric transmission cost recovery 19 20 14 10 5 10 WPL’s West Riverside liquidated damages 17 32 — — 17 32 Other 66 45 38 29 28 16 $1,208 $1,324 $676 $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 June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $957 $929 $868 $848 $89 $81 Pension and OPEB costs 378 392 190 197 188 195 Assets retired early 290 70 274 53 16 17 Asset retirement obligations 197 151 156 110 41 41 Commodity cost recovery 145 160 6 1 139 159 Derivatives 102 84 41 48 61 36 IPL’s Duane Arnold Energy Center PPA amendment 54 66 54 66 — — WPL’s Western Wisconsin gas distribution expansion investments 47 48 — — 47 48 Other 174 146 59 63 115 83 $2,344 $2,046 $1,648 $1,386 $696 $660
Regulatory Liabilities	Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, December 31, June 30, December 31, June 30, December 31, Tax-related $572 $579 $301 $303 $271 $276 Cost of removal obligations 405 398 260 259 145 139 Derivatives 90 210 48 115 42 95 Commodity cost recovery 39 40 15 38 24 2 Electric transmission cost recovery 19 20 14 10 5 10 WPL’s West Riverside liquidated damages 17 32 — — 17 32 Other 66 45 38 29 28 16 $1,208 $1,324 $676 $754 $532 $570

Receivables (Tables)

Receivables (Tables)	6 Months Ended
	Jun. 30, 2023
Receivables [Line Items]
Gross Write-offs For Accounts Receivable	For the three and six months ended June 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 Six Months Three Months Six Months Alliant Energy $3 $8 $2 $2 IPL 2 5 1 1 WPL 1 3 1 1
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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $110 $66 $110 $66 Average outstanding aggregate cash proceeds 101 18 79 11
Attributes of Receivables Sold Under the Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2023 December 31, 2022 Customer accounts receivable $148 $145 Unbilled utility revenues 100 132 Receivables sold to third party 248 277 Less: cash proceeds 60 80 Deferred proceeds 188 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $175 $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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Collections $514 $500 $1,104 $1,061 Write-offs, net of recoveries 2 1 4 3
IPL [Member]
Receivables [Line Items]
Gross Write-offs For Accounts Receivable	For the three and six months ended June 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 Six Months Three Months Six Months Alliant Energy $3 $8 $2 $2 IPL 2 5 1 1 WPL 1 3 1 1
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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Maximum outstanding aggregate cash proceeds $110 $66 $110 $66 Average outstanding aggregate cash proceeds 101 18 79 11
Attributes of Receivables Sold Under the Receivables Agreement	The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2023 December 31, 2022 Customer accounts receivable $148 $145 Unbilled utility revenues 100 132 Receivables sold to third party 248 277 Less: cash proceeds 60 80 Deferred proceeds 188 197 Less: allowance for expected credit losses 13 12 Fair value of deferred proceeds $175 $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 six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 Collections $514 $500 $1,104 $1,061 Write-offs, net of recoveries 2 1 4 3
WPL [Member]
Receivables [Line Items]
Gross Write-offs For Accounts Receivable	For the three and six months ended June 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 Six Months Three Months Six Months Alliant Energy $3 $8 $2 $2 IPL 2 5 1 1 WPL 1 3 1 1

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 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 six months ended June 30 was as follows (in millions): Three Months Six Months 2023 2022 2023 2022 ATC Holdings ($12) ($11) ($25) ($23) Other (2) (5) (6) (9) ($14) ($16) ($31) ($32)

Common Equity (Tables)

Common Equity (Tables)	6 Months Ended
	Jun. 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 1,221,775 Shareowner Direct Plan 228,017 Equity-based compensation plans 134,334 Shares outstanding, June 30, 2023 252,719,092
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 (Loss) Trust Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $— $6,328 Net income attributable to Alliant Energy common shareowners 160 160 Common stock dividends ($0.4525 per share) (113) (113) At-the-market offering program and Shareowner Direct Plan issuances 70 70 Equity-based compensation plans and other 4 (1) 3 Other comprehensive income, net of tax 4 4 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Net income attributable to Alliant Energy common shareowners 159 159 Common stock dividends ($0.4275 per share) (108) (108) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 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 (Loss) Trust Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 323 323 Common stock dividends ($0.905 per share) (226) (226) At-the-market offering program and Shareowner Direct Plan issuances 76 76 Equity-based compensation plans and other 1 (1) — Other comprehensive income, net of tax 3 3 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 351 351 Common stock dividends ($0.855 per share) (215) (215) Shareowner Direct Plan issuances 13 13 Equity-based compensation plans and other (3) 1 (2) Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $33 $2,807 $970 $3,810 Net income 89 89 Common stock dividends (70) (70) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $33 $2,807 $935 $3,775 Net income 87 87 Common stock dividends (80) (80) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 161 161 Common stock dividends (140) (140) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 173 173 Common stock dividends (160) (160) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $66 $2,413 $1,234 $— $3,713 Net income 72 72 Common stock dividends (46) (46) Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $66 $1,884 $1,101 $— $3,051 Net income 63 63 Common stock dividends (44) (44) Capital contributions from parent 85 85 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 160 160 Common stock dividends (92) (92) Capital contributions from parent 180 180 Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 156 156 Common stock dividends (89) (89) Capital contributions from parent 265 265 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183
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 (Loss) Trust Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $— $6,328 Net income attributable to Alliant Energy common shareowners 160 160 Common stock dividends ($0.4525 per share) (113) (113) At-the-market offering program and Shareowner Direct Plan issuances 70 70 Equity-based compensation plans and other 4 (1) 3 Other comprehensive income, net of tax 4 4 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Net income attributable to Alliant Energy common shareowners 159 159 Common stock dividends ($0.4275 per share) (108) (108) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 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 (Loss) Trust Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 323 323 Common stock dividends ($0.905 per share) (226) (226) At-the-market offering program and Shareowner Direct Plan issuances 76 76 Equity-based compensation plans and other 1 (1) — Other comprehensive income, net of tax 3 3 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 351 351 Common stock dividends ($0.855 per share) (215) (215) Shareowner Direct Plan issuances 13 13 Equity-based compensation plans and other (3) 1 (2) Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $33 $2,807 $970 $3,810 Net income 89 89 Common stock dividends (70) (70) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $33 $2,807 $935 $3,775 Net income 87 87 Common stock dividends (80) (80) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 161 161 Common stock dividends (140) (140) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 173 173 Common stock dividends (160) (160) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $66 $2,413 $1,234 $— $3,713 Net income 72 72 Common stock dividends (46) (46) Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $66 $1,884 $1,101 $— $3,051 Net income 63 63 Common stock dividends (44) (44) Capital contributions from parent 85 85 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 160 160 Common stock dividends (92) (92) Capital contributions from parent 180 180 Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 156 156 Common stock dividends (89) (89) Capital contributions from parent 265 265 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183
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 (Loss) Trust Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $3 $2,780 $3,559 ($1) ($13) $— $6,328 Net income attributable to Alliant Energy common shareowners 160 160 Common stock dividends ($0.4525 per share) (113) (113) At-the-market offering program and Shareowner Direct Plan issuances 70 70 Equity-based compensation plans and other 4 (1) 3 Other comprehensive income, net of tax 4 4 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $3 $2,750 $3,336 $— ($12) $— $6,077 Net income attributable to Alliant Energy common shareowners 159 159 Common stock dividends ($0.4275 per share) (108) (108) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 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 (Loss) Trust Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $3 $2,777 $3,509 $— ($13) $— $6,276 Net income attributable to Alliant Energy common shareowners 323 323 Common stock dividends ($0.905 per share) (226) (226) At-the-market offering program and Shareowner Direct Plan issuances 76 76 Equity-based compensation plans and other 1 (1) — Other comprehensive income, net of tax 3 3 Ending balance, June 30, 2023 $3 $2,854 $3,606 $3 ($14) $— $6,452 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $3 $2,749 $3,250 $— ($12) $— $5,990 Net income attributable to Alliant Energy common shareowners 351 351 Common stock dividends ($0.855 per share) (215) (215) Shareowner Direct Plan issuances 13 13 Equity-based compensation plans and other (3) 1 (2) Contributions from noncontrolling interest 29 29 Ending balance, June 30, 2022 $3 $2,759 $3,387 $— ($12) $29 $6,166 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $33 $2,807 $970 $3,810 Net income 89 89 Common stock dividends (70) (70) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $33 $2,807 $935 $3,775 Net income 87 87 Common stock dividends (80) (80) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $33 $2,807 $968 $3,808 Net income 161 161 Common stock dividends (140) (140) Capital contributions from parent 40 40 Ending balance, June 30, 2023 $33 $2,847 $989 $3,869 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $33 $2,807 $929 $3,769 Net income 173 173 Common stock dividends (160) (160) Ending balance, June 30, 2022 $33 $2,807 $942 $3,782 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Three Months Ended June 30, 2023 Beginning balance, March 31, 2023 $66 $2,413 $1,234 $— $3,713 Net income 72 72 Common stock dividends (46) (46) Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Three Months Ended June 30, 2022 Beginning balance, March 31, 2022 $66 $1,884 $1,101 $— $3,051 Net income 63 63 Common stock dividends (44) (44) Capital contributions from parent 85 85 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183 WPL Total WPL Common Equity Additional Common Paid-In Retained Noncontrolling Total Stock Capital Earnings Interest Equity Six Months Ended June 30, 2023 Beginning balance, December 31, 2022 $66 $2,233 $1,192 $— $3,491 Net income 160 160 Common stock dividends (92) (92) Capital contributions from parent 180 180 Ending balance, June 30, 2023 $66 $2,413 $1,260 $— $3,739 Six Months Ended June 30, 2022 Beginning balance, December 31, 2021 $66 $1,704 $1,053 $— $2,823 Net income 156 156 Common stock dividends (89) (89) Capital contributions from parent 265 265 Contributions from noncontrolling interest 29 29 Other (1) (1) Ending balance, June 30, 2022 $66 $1,968 $1,120 $29 $3,183

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 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): June 30, 2023 Alliant Energy IPL WPL Amount outstanding $391 $— $44 Weighted average interest rates 5.3% —% 5.2% Available credit facility capacity (a) $554 $195 $256 Alliant Energy IPL WPL Three Months Ended June 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $391 $441 $70 $— $91 $222 Average amount outstanding (based on daily outstanding balances) $88 $337 $6 $— $18 $166 Weighted average interest rates 5.3% 1.0% 5.3% —% 5.2% 0.9% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $330 $390 $3 $— $160 $185 Weighted average interest rates 4.8% 0.6% 5.3% —% 4.8% 0.5% (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2023.
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): June 30, 2023 Alliant Energy IPL WPL Amount outstanding $391 $— $44 Weighted average interest rates 5.3% —% 5.2% Available credit facility capacity (a) $554 $195 $256 Alliant Energy IPL WPL Three Months Ended June 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $391 $441 $70 $— $91 $222 Average amount outstanding (based on daily outstanding balances) $88 $337 $6 $— $18 $166 Weighted average interest rates 5.3% 1.0% 5.3% —% 5.2% 0.9% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $330 $390 $3 $— $160 $185 Weighted average interest rates 4.8% 0.6% 5.3% —% 4.8% 0.5% (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2023.
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): June 30, 2023 Alliant Energy IPL WPL Amount outstanding $391 $— $44 Weighted average interest rates 5.3% —% 5.2% Available credit facility capacity (a) $554 $195 $256 Alliant Energy IPL WPL Three Months Ended June 30 2023 2022 2023 2022 2023 2022 Maximum amount outstanding (based on daily outstanding balances) $391 $441 $70 $— $91 $222 Average amount outstanding (based on daily outstanding balances) $88 $337 $6 $— $18 $166 Weighted average interest rates 5.3% 1.0% 5.3% —% 5.2% 0.9% Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $793 $577 $70 $— $349 $252 Average amount outstanding (based on daily outstanding balances) $330 $390 $3 $— $160 $185 Weighted average interest rates 4.8% 0.6% 5.3% —% 4.8% 0.5% (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2023.

Revenues (Tables)

Revenues (Tables)	6 Months Ended
	Jun. 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 June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $284 $289 $151 $158 $133 $131 Retail - commercial 201 196 129 127 72 69 Retail - industrial 245 244 130 136 115 108 Wholesale 49 54 14 16 35 38 Bulk power and other 20 29 7 5 13 24 Total Electric Utility 799 812 431 442 368 370 Gas Utility: Retail - residential 42 51 24 28 18 23 Retail - commercial 22 27 12 14 10 13 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 13 6 8 4 5 Total Gas Utility 77 94 44 52 33 42 Other Utility: Steam 11 11 11 11 — — Other utility 2 2 1 1 1 1 Total Other Utility 13 13 12 12 1 1 Non-Utility and Other: Travero and other 23 24 — — — — Total Non-Utility and Other 23 24 — — — — Total revenues $912 $943 $487 $506 $402 $413 Alliant Energy IPL WPL Six Months Ended June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $569 $581 $294 $308 $275 $273 Retail - commercial 385 386 241 246 144 140 Retail - industrial 460 453 236 246 224 207 Wholesale 95 101 26 31 69 70 Bulk power and other 58 65 22 12 36 53 Total Electric Utility 1,567 1,586 819 843 748 743 Gas Utility: Retail - residential 210 210 117 113 93 97 Retail - commercial 110 109 56 54 54 55 Retail - industrial 9 11 6 7 3 4 Transportation/other 24 26 15 17 9 9 Total Gas Utility 353 356 194 191 159 165 Other Utility: Steam 22 20 22 20 — — Other utility 3 3 2 2 1 1 Total Other Utility 25 23 24 22 1 1 Non-Utility and Other: Travero and other 45 47 — — — — Total Non-Utility and Other 45 47 — — — — Total revenues $1,990 $2,012 $1,037 $1,056 $908 $909
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 June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $284 $289 $151 $158 $133 $131 Retail - commercial 201 196 129 127 72 69 Retail - industrial 245 244 130 136 115 108 Wholesale 49 54 14 16 35 38 Bulk power and other 20 29 7 5 13 24 Total Electric Utility 799 812 431 442 368 370 Gas Utility: Retail - residential 42 51 24 28 18 23 Retail - commercial 22 27 12 14 10 13 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 13 6 8 4 5 Total Gas Utility 77 94 44 52 33 42 Other Utility: Steam 11 11 11 11 — — Other utility 2 2 1 1 1 1 Total Other Utility 13 13 12 12 1 1 Non-Utility and Other: Travero and other 23 24 — — — — Total Non-Utility and Other 23 24 — — — — Total revenues $912 $943 $487 $506 $402 $413 Alliant Energy IPL WPL Six Months Ended June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $569 $581 $294 $308 $275 $273 Retail - commercial 385 386 241 246 144 140 Retail - industrial 460 453 236 246 224 207 Wholesale 95 101 26 31 69 70 Bulk power and other 58 65 22 12 36 53 Total Electric Utility 1,567 1,586 819 843 748 743 Gas Utility: Retail - residential 210 210 117 113 93 97 Retail - commercial 110 109 56 54 54 55 Retail - industrial 9 11 6 7 3 4 Transportation/other 24 26 15 17 9 9 Total Gas Utility 353 356 194 191 159 165 Other Utility: Steam 22 20 22 20 — — Other utility 3 3 2 2 1 1 Total Other Utility 25 23 24 22 1 1 Non-Utility and Other: Travero and other 45 47 — — — — Total Non-Utility and Other 45 47 — — — — Total revenues $1,990 $2,012 $1,037 $1,056 $908 $909
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 June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $284 $289 $151 $158 $133 $131 Retail - commercial 201 196 129 127 72 69 Retail - industrial 245 244 130 136 115 108 Wholesale 49 54 14 16 35 38 Bulk power and other 20 29 7 5 13 24 Total Electric Utility 799 812 431 442 368 370 Gas Utility: Retail - residential 42 51 24 28 18 23 Retail - commercial 22 27 12 14 10 13 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 13 6 8 4 5 Total Gas Utility 77 94 44 52 33 42 Other Utility: Steam 11 11 11 11 — — Other utility 2 2 1 1 1 1 Total Other Utility 13 13 12 12 1 1 Non-Utility and Other: Travero and other 23 24 — — — — Total Non-Utility and Other 23 24 — — — — Total revenues $912 $943 $487 $506 $402 $413 Alliant Energy IPL WPL Six Months Ended June 30 2023 2022 2023 2022 2023 2022 Electric Utility: Retail - residential $569 $581 $294 $308 $275 $273 Retail - commercial 385 386 241 246 144 140 Retail - industrial 460 453 236 246 224 207 Wholesale 95 101 26 31 69 70 Bulk power and other 58 65 22 12 36 53 Total Electric Utility 1,567 1,586 819 843 748 743 Gas Utility: Retail - residential 210 210 117 113 93 97 Retail - commercial 110 109 56 54 54 55 Retail - industrial 9 11 6 7 3 4 Transportation/other 24 26 15 17 9 9 Total Gas Utility 353 356 194 191 159 165 Other Utility: Steam 22 20 22 20 — — Other utility 3 3 2 2 1 1 Total Other Utility 25 23 24 22 1 1 Non-Utility and Other: Travero and other 45 47 — — — — Total Non-Utility and Other 45 47 — — — — Total revenues $1,990 $2,012 $1,037 $1,056 $908 $909

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2023
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate —% 2% (1%) 3% (17%) (16%) (18%) (15%) 16% 18% 14% 18%
Summary Of Tax Credit Carryforwards	At June 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 $503 $8 $1 Federal tax credits 2030-2043 708 485 214
IPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate —% 2% (1%) 3% (17%) (16%) (18%) (15%) 16% 18% 14% 18%
Summary Of Tax Credit Carryforwards	At June 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 $503 $8 $1 Federal tax credits 2030-2043 708 485 214
WPL [Member]
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rates	Overall effective income tax rates, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Overall income tax rate —% 2% (1%) 3% (17%) (16%) (18%) (15%) 16% 18% 14% 18%
Summary Of Tax Credit Carryforwards	At June 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 $503 $8 $1 Federal tax credits 2030-2043 708 485 214

Benefit Plans (Tables)

Benefit Plans (Tables)	6 Months Ended
	Jun. 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 six months ended June 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 Six Months Three Months Six Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $2 $2 $4 $— $1 $1 $2 Interest cost 12 9 23 18 2 2 4 3 Expected return on plan assets (13) (17) (26) (34) (1) (2) (2) (3) Amortization of actuarial loss 7 8 14 16 1 — 1 1 $7 $2 $13 $4 $2 $1 $4 $3 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $2 $3 $— $1 $— $1 Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (13) (16) (1) (1) (2) (2) Amortization of actuarial loss 3 4 6 7 1 — 1 — $3 $1 $5 $2 $1 $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $1 $2 $— $— $— $— Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (11) (16) — — — — Amortization of actuarial loss 4 4 7 8 — 1 — 1 $4 $1 $7 $2 $1 $1 $2 $2
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 six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $3 $3 $6 $7 $2 $1 $3 $4 $1 $1 $2 $3 Income tax benefits 1 1 2 2 — — 1 1 — — 1 1
Schedule Of Equity-based Compensation Plans Activity	For the six months ended June 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 106,927 $55.68 Performance restricted stock units 122,178 52.77 Restricted stock units 104,849 52.81
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 six months ended June 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 Six Months Three Months Six Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $2 $2 $4 $— $1 $1 $2 Interest cost 12 9 23 18 2 2 4 3 Expected return on plan assets (13) (17) (26) (34) (1) (2) (2) (3) Amortization of actuarial loss 7 8 14 16 1 — 1 1 $7 $2 $13 $4 $2 $1 $4 $3 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $2 $3 $— $1 $— $1 Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (13) (16) (1) (1) (2) (2) Amortization of actuarial loss 3 4 6 7 1 — 1 — $3 $1 $5 $2 $1 $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $1 $2 $— $— $— $— Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (11) (16) — — — — Amortization of actuarial loss 4 4 7 8 — 1 — 1 $4 $1 $7 $2 $1 $1 $2 $2
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 six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $3 $3 $6 $7 $2 $1 $3 $4 $1 $1 $2 $3 Income tax benefits 1 1 2 2 — — 1 1 — — 1 1
Schedule Of Equity-based Compensation Plans Activity	For the six months ended June 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 106,927 $55.68 Performance restricted stock units 122,178 52.77 Restricted stock units 104,849 52.81
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 six months ended June 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 Six Months Three Months Six Months Alliant Energy 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $2 $2 $4 $— $1 $1 $2 Interest cost 12 9 23 18 2 2 4 3 Expected return on plan assets (13) (17) (26) (34) (1) (2) (2) (3) Amortization of actuarial loss 7 8 14 16 1 — 1 1 $7 $2 $13 $4 $2 $1 $4 $3 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $2 $3 $— $1 $— $1 Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (13) (16) (1) (1) (2) (2) Amortization of actuarial loss 3 4 6 7 1 — 1 — $3 $1 $5 $2 $1 $— $1 $— Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2023 2022 2023 2022 2023 2022 2023 2022 Service cost $1 $1 $1 $2 $— $— $— $— Interest cost 5 4 10 8 1 — 2 1 Expected return on plan assets (6) (8) (11) (16) — — — — Amortization of actuarial loss 4 4 7 8 — 1 — 1 $4 $1 $7 $2 $1 $1 $2 $2
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 six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 2023 2022 Compensation expense $3 $3 $6 $7 $2 $1 $3 $4 $1 $1 $2 $3 Income tax benefits 1 1 2 2 — — 1 1 — — 1 1
Schedule Of Equity-based Compensation Plans Activity	For the six months ended June 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 106,927 $55.68 Performance restricted stock units 122,178 52.77 Restricted stock units 104,849 52.81

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2023
Derivative Instruments [Line Items]
Notional Amounts Of Derivative Instruments	As of June 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 1,171 2023-2025 24,874 2023-2024 192,421 2023-2032 466 2023 IPL 537 2023-2025 10,163 2023-2024 92,087 2023-2030 224 2023 WPL 634 2023-2025 14,711 2023-2024 100,334 2023-2032 242 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 June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $86 $111 $61 $69 $25 $42 Non-current derivative assets 61 126 34 69 27 57 Current derivative liabilities 54 59 27 40 27 19 Non-current derivative liabilities 43 20 10 6 33 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 June 30, 2023 Derivative assets $147 $114 $95 $73 $52 $41 Derivative liabilities 97 64 37 15 60 49 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 June 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 1,171 2023-2025 24,874 2023-2024 192,421 2023-2032 466 2023 IPL 537 2023-2025 10,163 2023-2024 92,087 2023-2030 224 2023 WPL 634 2023-2025 14,711 2023-2024 100,334 2023-2032 242 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 June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $86 $111 $61 $69 $25 $42 Non-current derivative assets 61 126 34 69 27 57 Current derivative liabilities 54 59 27 40 27 19 Non-current derivative liabilities 43 20 10 6 33 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 June 30, 2023 Derivative assets $147 $114 $95 $73 $52 $41 Derivative liabilities 97 64 37 15 60 49 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 June 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 1,171 2023-2025 24,874 2023-2024 192,421 2023-2032 466 2023 IPL 537 2023-2025 10,163 2023-2024 92,087 2023-2030 224 2023 WPL 634 2023-2025 14,711 2023-2024 100,334 2023-2032 242 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 June 30, December 31, June 30, December 31, June 30, December 31, Current derivative assets $86 $111 $61 $69 $25 $42 Non-current derivative assets 61 126 34 69 27 57 Current derivative liabilities 54 59 27 40 27 19 Non-current derivative liabilities 43 20 10 6 33 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 June 30, 2023 Derivative assets $147 $114 $95 $73 $52 $41 Derivative liabilities 97 64 37 15 60 49 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)	6 Months Ended
	Jun. 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 June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 147 — 80 67 147 237 — 206 31 237 Interest rate derivatives 4 — 4 — 4 — — — — — Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 97 — 84 13 97 79 — 67 12 79 Long-term debt (incl. current maturities) 8,595 — 7,950 1 7,951 8,076 — 7,338 1 7,339 IPL June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 95 — 44 51 95 138 — 111 27 138 Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 37 — 27 10 37 46 — 35 11 46 Long-term debt 3,702 — 3,321 — 3,321 3,646 — 3,228 — 3,228 WPL June 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 $52 $— $36 $16 $52 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 60 — 57 3 60 33 — 32 1 33 Long-term debt 3,068 — 2,875 — 2,875 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 June 30 2023 2022 2023 2022 Beginning balance, April 1 ($5) $10 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (7) (10) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) 5 (7) 22 17 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($7) ($10) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (11) (16) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) (15) (20) (10) 30 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($11) ($16) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2023 2022 2023 2022 Beginning balance, April 1 $— $7 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (13) (3) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) 4 (4) 22 17 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($13) ($3) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (12) (7) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) (13) (11) (10) 30 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($12) ($8) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2023 2022 Beginning balance, April 1 ($5) $3 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (7) Purchases 11 21 Settlements 1 (3) Ending balance, June 30 $13 $14 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 June 30 $6 ($7) WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (9) Purchases 11 21 Settlements (2) (9) Ending balance, June 30 $13 $14 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 June 30 $1 ($8) (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 June 30, 2023 ($8) $62 ($5) $46 ($3) $16 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 June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 147 — 80 67 147 237 — 206 31 237 Interest rate derivatives 4 — 4 — 4 — — — — — Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 97 — 84 13 97 79 — 67 12 79 Long-term debt (incl. current maturities) 8,595 — 7,950 1 7,951 8,076 — 7,338 1 7,339 IPL June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 95 — 44 51 95 138 — 111 27 138 Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 37 — 27 10 37 46 — 35 11 46 Long-term debt 3,702 — 3,321 — 3,321 3,646 — 3,228 — 3,228 WPL June 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 $52 $— $36 $16 $52 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 60 — 57 3 60 33 — 32 1 33 Long-term debt 3,068 — 2,875 — 2,875 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 June 30 2023 2022 2023 2022 Beginning balance, April 1 ($5) $10 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (7) (10) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) 5 (7) 22 17 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($7) ($10) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (11) (16) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) (15) (20) (10) 30 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($11) ($16) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2023 2022 2023 2022 Beginning balance, April 1 $— $7 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (13) (3) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) 4 (4) 22 17 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($13) ($3) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (12) (7) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) (13) (11) (10) 30 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($12) ($8) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2023 2022 Beginning balance, April 1 ($5) $3 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (7) Purchases 11 21 Settlements 1 (3) Ending balance, June 30 $13 $14 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 June 30 $6 ($7) WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (9) Purchases 11 21 Settlements (2) (9) Ending balance, June 30 $13 $14 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 June 30 $1 ($8) (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 June 30, 2023 ($8) $62 ($5) $46 ($3) $16 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 June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 147 — 80 67 147 237 — 206 31 237 Interest rate derivatives 4 — 4 — 4 — — — — — Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 97 — 84 13 97 79 — 67 12 79 Long-term debt (incl. current maturities) 8,595 — 7,950 1 7,951 8,076 — 7,338 1 7,339 IPL June 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 $6 $6 $— $— $6 $10 $10 $— $— $10 Commodity derivatives 95 — 44 51 95 138 — 111 27 138 Deferred proceeds 175 — — 175 175 185 — — 185 185 Liabilities: Commodity derivatives 37 — 27 10 37 46 — 35 11 46 Long-term debt 3,702 — 3,321 — 3,321 3,646 — 3,228 — 3,228 WPL June 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 $52 $— $36 $16 $52 $99 $— $95 $4 $99 Liabilities: Commodity derivatives 60 — 57 3 60 33 — 32 1 33 Long-term debt 3,068 — 2,875 — 2,875 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 June 30 2023 2022 2023 2022 Beginning balance, April 1 ($5) $10 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (7) (10) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) 5 (7) 22 17 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($7) ($10) $— $— Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $19 $29 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (11) (16) — — Purchases 62 79 — — Sales (1) — — — Settlements (a) (15) (20) (10) 30 Ending balance, June 30 $54 $72 $175 $244 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 June 30 ($11) ($16) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2023 2022 2023 2022 Beginning balance, April 1 $— $7 $153 $227 Total net losses included in changes in net assets (realized/unrealized) (13) (3) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) 4 (4) 22 17 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($13) ($3) $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2023 2022 2023 2022 Beginning balance, January 1 $16 $18 $185 $214 Total net losses included in changes in net assets (realized/unrealized) (12) (7) — — Purchases 51 58 — — Sales (1) — — — Settlements (a) (13) (11) (10) 30 Ending balance, June 30 $41 $58 $175 $244 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 June 30 ($12) ($8) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2023 2022 Beginning balance, April 1 ($5) $3 Total net gains (losses) included in changes in net assets (realized/unrealized) 6 (7) Purchases 11 21 Settlements 1 (3) Ending balance, June 30 $13 $14 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 June 30 $6 ($7) WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2023 2022 Beginning balance, January 1 $3 $11 Total net gains (losses) included in changes in net assets (realized/unrealized) 1 (9) Purchases 11 21 Settlements (2) (9) Ending balance, June 30 $13 $14 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 June 30 $1 ($8) (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 June 30, 2023 ($8) $62 ($5) $46 ($3) $16 December 31, 2022 (10) 29 (9) 25 (1) 4

Commitments And Contingencies (

Commitments And Contingencies (Tables)	6 Months Ended
	Jun. 30, 2023
Commitments and Contingencies [Line Items]
Other Purchase Commitments	At June 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,083 $494 $589 Coal 163 79 84 Other (a) 106 51 25 $1,352 $624 $698 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At June 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 June 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,083 $494 $589 Coal 163 79 84 Other (a) 106 51 25 $1,352 $624 $698 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At June 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 June 30, 2023, related minimum future commitments were as follows (in millions): Alliant Energy IPL WPL Natural gas $1,083 $494 $589 Coal 163 79 84 Other (a) 106 51 25 $1,352 $624 $698 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at June 30, 2023.
MGP Site Estimated Future Costs And Recorded Liabilities	At June 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)	6 Months Ended
	Jun. 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 June 30, 2023 Revenues $799 $77 $13 $889 $23 $912 Operating income 200 2 7 209 8 217 Net income (loss) attributable to Alliant Energy common shareowners 161 (1) 160 Three Months Ended June 30, 2022 Revenues $812 $94 $13 $919 $24 $943 Operating income 195 8 1 204 8 212 Net income attributable to Alliant Energy common shareowners 150 9 159 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2023 Revenues $1,567 $353 $25 $1,945 $45 $1,990 Operating income 363 52 11 426 13 439 Net income attributable to Alliant Energy common shareowners 321 2 323 Six Months Ended June 30, 2022 Revenues $1,586 $356 $23 $1,965 $47 $2,012 Operating income 376 65 4 445 15 460 Net income attributable to Alliant Energy common shareowners 329 22 351 IPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $431 $44 $12 $487 Operating income 105 — 5 110 Net income 89 Three Months Ended June 30, 2022 Revenues $442 $52 $12 $506 Operating income 104 4 1 109 Net income 87 Six Months Ended June 30, 2023 Revenues $819 $194 $24 $1,037 Operating income 171 27 8 206 Net income 161 Six Months Ended June 30, 2022 Revenues $843 $191 $22 $1,056 Operating income 179 36 3 218 Net income 173 WPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $368 $33 $1 $402 Operating income 95 2 2 99 Net income 72 Three Months Ended June 30, 2022 Revenues $370 $42 $1 $413 Operating income 91 4 — 95 Net income 63 Six Months Ended June 30, 2023 Revenues $748 $159 $1 $908 Operating income 192 25 3 220 Net income 160 Six Months Ended June 30, 2022 Revenues $743 $165 $1 $909 Operating income 197 29 1 227 Net income 156
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 June 30, 2023 Revenues $799 $77 $13 $889 $23 $912 Operating income 200 2 7 209 8 217 Net income (loss) attributable to Alliant Energy common shareowners 161 (1) 160 Three Months Ended June 30, 2022 Revenues $812 $94 $13 $919 $24 $943 Operating income 195 8 1 204 8 212 Net income attributable to Alliant Energy common shareowners 150 9 159 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2023 Revenues $1,567 $353 $25 $1,945 $45 $1,990 Operating income 363 52 11 426 13 439 Net income attributable to Alliant Energy common shareowners 321 2 323 Six Months Ended June 30, 2022 Revenues $1,586 $356 $23 $1,965 $47 $2,012 Operating income 376 65 4 445 15 460 Net income attributable to Alliant Energy common shareowners 329 22 351 IPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $431 $44 $12 $487 Operating income 105 — 5 110 Net income 89 Three Months Ended June 30, 2022 Revenues $442 $52 $12 $506 Operating income 104 4 1 109 Net income 87 Six Months Ended June 30, 2023 Revenues $819 $194 $24 $1,037 Operating income 171 27 8 206 Net income 161 Six Months Ended June 30, 2022 Revenues $843 $191 $22 $1,056 Operating income 179 36 3 218 Net income 173 WPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $368 $33 $1 $402 Operating income 95 2 2 99 Net income 72 Three Months Ended June 30, 2022 Revenues $370 $42 $1 $413 Operating income 91 4 — 95 Net income 63 Six Months Ended June 30, 2023 Revenues $748 $159 $1 $908 Operating income 192 25 3 220 Net income 160 Six Months Ended June 30, 2022 Revenues $743 $165 $1 $909 Operating income 197 29 1 227 Net income 156
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 June 30, 2023 Revenues $799 $77 $13 $889 $23 $912 Operating income 200 2 7 209 8 217 Net income (loss) attributable to Alliant Energy common shareowners 161 (1) 160 Three Months Ended June 30, 2022 Revenues $812 $94 $13 $919 $24 $943 Operating income 195 8 1 204 8 212 Net income attributable to Alliant Energy common shareowners 150 9 159 Alliant Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Six Months Ended June 30, 2023 Revenues $1,567 $353 $25 $1,945 $45 $1,990 Operating income 363 52 11 426 13 439 Net income attributable to Alliant Energy common shareowners 321 2 323 Six Months Ended June 30, 2022 Revenues $1,586 $356 $23 $1,965 $47 $2,012 Operating income 376 65 4 445 15 460 Net income attributable to Alliant Energy common shareowners 329 22 351 IPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $431 $44 $12 $487 Operating income 105 — 5 110 Net income 89 Three Months Ended June 30, 2022 Revenues $442 $52 $12 $506 Operating income 104 4 1 109 Net income 87 Six Months Ended June 30, 2023 Revenues $819 $194 $24 $1,037 Operating income 171 27 8 206 Net income 161 Six Months Ended June 30, 2022 Revenues $843 $191 $22 $1,056 Operating income 179 36 3 218 Net income 173 WPL Electric Gas Other Total (in millions) Three Months Ended June 30, 2023 Revenues $368 $33 $1 $402 Operating income 95 2 2 99 Net income 72 Three Months Ended June 30, 2022 Revenues $370 $42 $1 $413 Operating income 91 4 — 95 Net income 63 Six Months Ended June 30, 2023 Revenues $748 $159 $1 $908 Operating income 192 25 3 220 Net income 160 Six Months Ended June 30, 2022 Revenues $743 $165 $1 $909 Operating income 197 29 1 227 Net income 156

Related Parties (Tables)

Related Parties (Tables)	6 Months Ended
	Jun. 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 six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $48 $51 $88 $91 $43 $42 $80 $78 Sales credited 1 — 8 — 10 13 22 31 Purchases billed 94 129 187 223 2 39 17 61
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2023 December 31, 2022 June 30, 2023 December 31, 2022 Net payables to Corporate Services $116 $103 $73 $56
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 ATC billings to WPL $44 $35 $78 $69 WPL billings to ATC 5 5 11 8
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 six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $48 $51 $88 $91 $43 $42 $80 $78 Sales credited 1 — 8 — 10 13 22 31 Purchases billed 94 129 187 223 2 39 17 61
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2023 December 31, 2022 June 30, 2023 December 31, 2022 Net payables to Corporate Services $116 $103 $73 $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 six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2023 2022 2023 2022 2023 2022 2023 2022 Corporate Services billings $48 $51 $88 $91 $43 $42 $80 $78 Sales credited 1 — 8 — 10 13 22 31 Purchases billed 94 129 187 223 2 39 17 61
Net Intercompany Payables	Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2023 December 31, 2022 June 30, 2023 December 31, 2022 Net payables to Corporate Services $116 $103 $73 $56
Related Amounts Billed Between Parties	The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2023 2022 2023 2022 ATC billings to WPL $44 $35 $78 $69 WPL billings to ATC 5 5 11 8

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Regulatory Matters [Line Items]
Regulatory assets	$ 2,344	$ 2,046
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	1,648	1,386
WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	696	660
Assets retired early [Member]
Regulatory Matters [Line Items]
Regulatory assets	290	70
Assets retired early [Member] | IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	274	53
Assets retired early [Member] | WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	16	$ 17
Assets retired early [Member] | Lansing Generating Station
Regulatory Matters [Line Items]
Regulatory assets	226
Assets retired early [Member] | Lansing Generating Station | IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets	$ 226

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory assets	$ 2,344	$ 2,046
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	957	929
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	378	392
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	290	70
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	197	151
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	145	160
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	102	84
IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	54	66
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	47	48
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	174	146
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,648	1,386
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	868	848
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	190	197
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	274	53
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	156	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	6	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	41	48
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	54	66
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	59	63
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	696	660
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	89	81
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	188	195
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	16	17
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	41	41
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	139	159
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	61	36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	47	48
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 115	$ 83

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,208	$ 1,324
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	572	579
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	405	398
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	90	210
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	39	40
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	19	20
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	17	32
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	66	45
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	676	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	260	259
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	48	115
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	15	38
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	14	10
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	38	29
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	532	570
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	271	276
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	145	139
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	42	95
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	24	2
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	5	10
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	17	32
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 28	$ 16

Property, Plant and Equipment (

Property, Plant and Equipment (Narrative) (Details)	Jun. 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] $ in Millions	Jun. 30, 2023 USD ($)
Receivables [Line Items]
Available capacity	$ 50
Financial Asset, Past Due [Member]
Receivables [Line Items]
Outstanding receivables past due	$ 20

Receivables (Gross Write-offs F

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

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Maximum [Member]
Receivables [Line Items]
Maximum outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 110	$ 66	$ 110	$ 66
Average [Member]
Receivables [Line Items]
Average outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 101	$ 18	$ 79	$ 11

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Receivables [Line Items]
Fair value of deferred proceeds	$ 175	$ 185
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	175	185
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	148	145
Unbilled utility revenues	100	132
Receivables sold to third party	248	277
Less: cash proceeds	60	80
Deferred proceeds	188	197
Less: allowance for expected credit losses	13	12
Fair value of deferred proceeds	$ 175	$ 185

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Receivables [Line Items]
Collections	$ 514	$ 500	$ 1,104	$ 1,061
Write-offs, net of recoveries	$ 2	$ 1	$ 4	$ 3

Investments (Unconsolidated Equ

Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (14)	$ (16)	$ (31)	$ (32)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(12)	(11)	(25)	(23)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	(2)	(5)	(6)	(9)
Total [Member]
Schedule of Equity Method Investments [Line Items]
Equity (income) loss from unconsolidated investments, net	$ (14)	$ (16)	$ (31)	$ (32)

Common Equity (Narrative) (Deta

Common Equity (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2023
Common Equity [Line Items]
Proceeds from issuance of common stock, net		$ 70	$ 6	$ 76	$ 13
Common stock issued during period, At-the-market offering program (in shares)				134,334
At The Market Offering Program
Common Equity [Line Items]
Proceeds from issuance of common stock, net				$ 64
Fees and commissions from issuance of common stock				$ 1
Common stock issued during period, At-the-market offering program (in shares)				1,221,775
At The Market Offering Program | Subsequent Event [Member]
Common Equity [Line Items]
Proceeds from issuance of common stock, net	$ 9
Common stock issued during period, At-the-market offering program (in shares)	172,701
At The Market Offering Program | 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) - shares	1 Months Ended	6 Months Ended
	Jul. 31, 2023	Jun. 30, 2023
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1, 2023 (in shares)	252,719,092	251,134,966
Shareowner Direct Plan (in shares)		228,017
Equity-based compensation plans (in shares)		134,334
Shares outstanding, June 30, 2023 (in shares)		252,719,092
At The Market Offering Program
Common Stock Oustanding [Roll Forward]
Equity-based compensation plans (in shares)		1,221,775
At The Market Offering Program | Subsequent Event [Member]
Common Stock Oustanding [Roll Forward]
Equity-based compensation plans (in shares)	172,701

Common Equity (Changes in Share

Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			$ 6,276
Beginning balance	$ 6,328	$ 6,077	6,276	$ 5,990
Net income attributable to common shareowners	160	159	323	351
Net income			323	351
Common stock dividends	(113)	(108)	(226)	(215)
At-the-market offering program and Shareowner Direct Plan issuances	70	6	76	13
Equity-based compensation plans and other	3	3	0	(2)
Other comprehensive income, net of tax	4		3
Contributions from noncontrolling interest		29	0	29
Ending balance	6,452		6,452
Ending balance	$ 6,452	$ 6,166	$ 6,452	$ 6,166
Common stock dividends (in dollars per share)	$ 0.4525	$ 0.4275	$ 0.905	$ 0.855
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 3	$ 3	$ 3	$ 3
At-the-market offering program and Shareowner Direct Plan issuances
Ending balance	3	3	3	3
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,780	2,750	2,777	2,749
At-the-market offering program and Shareowner Direct Plan issuances	70	6	76	13
Equity-based compensation plans and other	4	3	1	(3)
Ending balance	2,854	2,759	2,854	2,759
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,559	3,336	3,509	3,250
Net income attributable to common shareowners	160	159	323	351
Common stock dividends	(113)	(108)	(226)	(215)
Equity-based compensation plans and other				1
Ending balance	3,606	3,387	3,606	3,387
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(1)	0	0	0
Other comprehensive income, net of tax	4		3
Ending balance	3	0	3	0
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(13)	(12)	(13)	(12)
Equity-based compensation plans and other	(1)		(1)
Ending balance	(14)	(12)	(14)	(12)
Noncontrolling Interest [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	0	0	0
Contributions from noncontrolling interest		29		29
Ending balance	0	29	0	29
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,808
Beginning balance	3,810	3,775	3,808	3,769
Net income	89	87	161	173
Common stock dividends	(70)	(80)	(140)	(160)
Capital contributions from parent	40		40	0
Ending balance	3,869		3,869
Ending balance	3,869	3,782	3,869	3,782
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	2,807	2,807	2,807	2,807
Capital contributions from parent	40		40
Ending balance	2,847	2,807	2,847	2,807
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	970	935	968	929
Net income	89	87	161	173
Common stock dividends	(70)	(80)	(140)	(160)
Ending balance	989	942	989	942
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,491
Beginning balance	3,713	3,051	3,491	2,823
Net income	72	63	160	156
Common stock dividends	(46)	(44)	(92)	(89)
Equity-based compensation plans and other		(1)		(1)
Capital contributions from parent		85	180	265
Contributions from noncontrolling interest		29	0	29
Ending balance	3,739		3,739
Ending balance	3,739	3,183	3,739	3,183
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	1,884	2,233	1,704
Equity-based compensation plans and other		(1)		(1)
Capital contributions from parent		85	180	265
Ending balance	2,413	1,968	2,413	1,968
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,234	1,101	1,192	1,053
Net income	72	63	160	156
Common stock dividends	(46)	(44)	(92)	(89)
Ending balance	1,260	1,120	1,260	1,120
WPL [Member] | Noncontrolling Interest [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	0	0	0	0
Contributions from noncontrolling interest		29		29
Ending balance	$ 0	$ 29	$ 0	$ 29

Debt (Narrative) (Details)

Debt (Narrative) (Details)	6 Months Ended
	Jun. 30, 2023 USD ($) Integer $ / shares shares	Jun. 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	$ 304,000,000
Long-term commercial paper	$ 55,000,000
Long-term commercial paper, percent	5%
Long-term debt, fair value	$ 7,951,000,000		$ 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 commercial paper	$ 55,000,000
Long-term commercial paper, percent	5%
Long-term debt, fair value	$ 3,321,000,000		3,228,000,000
WPL [Member]
Debt [Line Items]
Line of credit facility, current borrowing capacity	300,000,000
Long-term debt, fair value	2,875,000,000		$ 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 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	$ 566,000,000
Unamortized debt issuance costs	9,000,000
Long-term debt, fair value	$ 573,000,000
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	Jun. 30, 2023 USD ($)
Debt [Line Items]
Amount outstanding	$ 391
Weighted average interest rates	5.30%
Available credit facility capacity	$ 554
IPL [Member]
Debt [Line Items]
Amount outstanding	$ 0
Weighted average interest rates	0%
Available credit facility capacity	$ 195
WPL [Member]
Debt [Line Items]
Amount outstanding	$ 44
Weighted average interest rates	5.20%
Available credit facility capacity	$ 256

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 391	$ 441	$ 793	$ 577
Average amount outstanding (based on daily outstanding balances)	$ 88	$ 337	$ 330	$ 390
Weighted average interest rates	5.30%	1%	4.80%	0.60%
IPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 70	$ 0	$ 70	$ 0
Average amount outstanding (based on daily outstanding balances)	$ 6	$ 0	$ 3	$ 0
Weighted average interest rates	5.30%	0%	5.30%	0%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 91	$ 222	$ 349	$ 252
Average amount outstanding (based on daily outstanding balances)	$ 18	$ 166	$ 160	$ 185
Weighted average interest rates	5.20%	0.90%	4.80%	0.50%

Revenue (Disaggregation of Reve

Revenue (Disaggregation of Revenues) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 912	$ 943	$ 1,990	$ 2,012
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	799	812	1,567	1,586
Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	284	289	569	581
Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	201	196	385	386
Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	245	244	460	453
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	49	54	95	101
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20	29	58	65
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	77	94	353	356
Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	42	51	210	210
Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	27	110	109
Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	3	9	11
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	13	24	26
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	13	25	23
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	11	22	20
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	3	3
Non-utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	24	45	47
Non-utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	24	45	47
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	487	506	1,037	1,056
IPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	431	442	819	843
IPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	151	158	294	308
IPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	129	127	241	246
IPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	130	136	236	246
IPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	16	26	31
IPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7	5	22	12
IPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44	52	194	191
IPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24	28	117	113
IPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	14	56	54
IPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	6	7
IPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	8	15	17
IPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	12	24	22
IPL [Member] | Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	11	22	20
IPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	2	2
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	402	413	908	909
WPL [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	368	370	748	743
WPL [Member] | Electric [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	133	131	275	273
WPL [Member] | Electric [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	72	69	144	140
WPL [Member] | Electric [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	115	108	224	207
WPL [Member] | Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	35	38	69	70
WPL [Member] | Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	24	36	53
WPL [Member] | Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	42	159	165
WPL [Member] | Gas [Member] | Retail - residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18	23	93	97
WPL [Member] | Gas [Member] | Retail - commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	13	54	55
WPL [Member] | Gas [Member] | Retail - industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	3	4
WPL [Member] | Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	5	9	9
WPL [Member] | Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	1	1
WPL [Member] | Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1	$ 1	$ 1	$ 1

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Effective Tax Rate [Line Items]
Overall income tax rate	0%	2%	(1.00%)	3%
IPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	(17.00%)	(16.00%)	(18.00%)	(15.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Overall income tax rate	16%	18%	14%	18%

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Jun. 30, 2023 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 503
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	708
IPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	8
IPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	485
WPL [Member] | State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] | Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 214

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($) shares
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 15
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	1 year
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost recognized over a weighted average period	2 years
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 8
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized compensation cost	$ 6
Omnibus Incentive Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Shares included in diluted earnings per share (in shares) | shares	206,177

Benefit Plans (Defined Benefit

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2	$ 2	$ 4
Interest cost	12	9	23	18
Expected return on plan assets	(13)	(17)	(26)	(34)
Amortization of actuarial loss	7	8	14	16
Total	7	2	13	4
OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1	2
Interest cost	2	2	4	3
Expected return on plan assets	(1)	(2)	(2)	(3)
Amortization of actuarial loss	1	0	1	1
Total	2	1	4	3
IPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2	3
Interest cost	5	4	10	8
Expected return on plan assets	(6)	(8)	(13)	(16)
Amortization of actuarial loss	3	4	6	7
Total	3	1	5	2
IPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	0	1
Interest cost	1	0	2	1
Expected return on plan assets	(1)	(1)	(2)	(2)
Amortization of actuarial loss	1	0	1	0
Total	1	0	1	0
WPL [Member] | Defined benefit pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1	2
Interest cost	5	4	10	8
Expected return on plan assets	(6)	(8)	(11)	(16)
Amortization of actuarial loss	4	4	7	8
Total	4	1	7	2
WPL [Member] | OPEB Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	1	0	2	1
Expected return on plan assets	0	0	0	0
Amortization of actuarial loss	0	1	0	1
Total	$ 1	$ 1	$ 2	$ 2

Benefit Plans (Recognized Compe

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Compensation expense	$ 3	$ 3	$ 6	$ 7
Income tax benefits	1	1	2	2
IPL [Member]
Compensation expense	2	1	3	4
Income tax benefits	0	0	1	1
WPL [Member]
Compensation expense	1	1	2	3
Income tax benefits	$ 0	$ 0	$ 1	$ 1

Benefit Plans (Summary Of Equit

Benefit Plans (Summary Of Equity-based Compensation Plans Grants) (Details)	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	106,927
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	122,178
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 52.77
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (in shares/units) | shares	104,849
Weighted average grant date fair value (in dollars per share/unit) | $ / shares	$ 52.81

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Derivative Instruments [Line Items]
Non-current interest rate swap liabilities	$ 534		$ 534		$ 518
Accumulated other comprehensive loss, interest rate swap	3		3		$ 0
Interest expense, interest rate swap	96	$ 78	190	$ 152
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	$ 4		$ 4
Accumulated other comprehensive loss, interest rate swap	3		3
Interest expense, interest rate swap	$ 1		$ 1

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] T in Thousands, MWh in Thousands, Dekatherms in Thousands	6 Months Ended
	Jun. 30, 2023 Dekatherms MWh T
Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	1,171
Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	537
Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	634
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	24,874
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	10,163
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	14,711
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	192,421
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	92,087
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	100,334
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	466
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	224
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	242

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 86	$ 111
Non-current derivative assets	61	126
Current derivative liabilities	54	59
Non-current derivative liabilities	43	20
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	61	69
Non-current derivative assets	34	69
Current derivative liabilities	27	40
Non-current derivative liabilities	10	6
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	25	42
Non-current derivative assets	27	57
Current derivative liabilities	27	19
Non-current derivative liabilities	$ 33	$ 14

Derivative Instruments (Balance

Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	$ 147	$ 237
Derivative assets, Net	114	193
Derivative liabilities, Gross (as reported)	97	79
Derivative liabilities, Net	64	35
IPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	95	138
Derivative assets, Net	73	108
Derivative liabilities, Gross (as reported)	37	46
Derivative liabilities, Net	15	16
WPL [Member]
Derivative Instruments [Line Items]
Derivative assets, Gross (as reported)	52	99
Derivative assets, Net	41	85
Derivative liabilities, Gross (as reported)	60	33
Derivative liabilities, Net	$ 49	$ 19

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Assets:
Money market fund investments	$ 6	$ 10
Deferred proceeds	175	185
Liabilities:
Long-term debt (incl. current maturities)	7,951	7,339
IPL [Member]
Assets:
Money market fund investments	6	10
Deferred proceeds	175	185
Liabilities:
Long-term debt (incl. current maturities)	3,321	3,228
WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,875	2,542
Commodity Contracts [Member]
Assets:
Derivatives	147	237
Liabilities:
Derivatives	97	79
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	95	138
Liabilities:
Derivatives	37	46
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	52	99
Liabilities:
Derivatives	60	33
Interest Rate Swap [Member]
Assets:
Derivatives	4	0
Level 1 [Member]
Assets:
Money market fund investments	6	10
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	6	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)	7,950	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)	3,321	3,228
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,875	2,542
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	80	206
Liabilities:
Derivatives	84	67
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	44	111
Liabilities:
Derivatives	27	35
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	36	95
Liabilities:
Derivatives	57	32
Level 2 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	4	0
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	175	185
Liabilities:
Long-term debt (incl. current maturities)	1	1
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	175	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	67	31
Liabilities:
Derivatives	13	12
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	51	27
Liabilities:
Derivatives	10	11
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	16	4
Liabilities:
Derivatives	3	1
Level 3 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	0
Carrying Amount [Member]
Assets:
Money market fund investments	6	10
Deferred proceeds	175	185
Liabilities:
Long-term debt (incl. current maturities)	8,595	8,076
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	6	10
Deferred proceeds	175	185
Liabilities:
Long-term debt (incl. current maturities)	3,702	3,646
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	3,068	2,770
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	147	237
Liabilities:
Derivatives	97	79
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	95	138
Liabilities:
Derivatives	37	46
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	52	99
Liabilities:
Derivatives	60	33
Carrying Amount [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	$ 4	$ 0

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (5)	$ 10	$ 19	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	(7)	(10)	(11)	(16)
Purchases	62	79	62	79
Sales	(1)	0	(1)	0
Settlements	5	(7)	(15)	(20)
Ending balance	54	72	54	72
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 June 30	(7)	(10)	(11)	(16)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	7	16	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	(13)	(3)	(12)	(7)
Purchases	51	58	51	58
Sales	(1)	0	(1)	0
Settlements	4	(4)	(13)	(11)
Ending balance	41	58	41	58
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 June 30	(13)	(3)	(12)	(8)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(5)	3	3	11
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	(7)	1	(9)
Purchases	11	21	11	21
Settlements	1	(3)	(2)	(9)
Ending balance	13	14	13	14
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 June 30	6	(7)	1	(8)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	153	227	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	22	17	(10)	30
Ending balance	175	244	175	244
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 June 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	153	227	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	22	17	(10)	30
Ending balance	175	244	175	244
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 June 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	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 54	$ (5)	$ 19	$ 72	$ 10	$ 29
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative liabilities	(8)		(10)
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	62		29
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	41	0	16	58	7	18
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative liabilities	(5)		(9)
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	46		25
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	13	$ (5)	3	$ 14	$ 3	$ 11
WPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative liabilities	(3)		(1)
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 16		$ 4

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended
	Jun. 30, 2023	Sep. 30, 2021	Sep. 30, 2020
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,352
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	624
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	698
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	188
Capital Purchase Commitment [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	87
Capital Purchase Commitment [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	101
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	59
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum	$ 17
Whiting Petroleum Affiliate [Member]
Commitments and Contingencies [Line Items]
Partnership share, percent	6%
Obligations, maximum	$ 58
Credit loss liability	$ 5
Federal Energy Regulatory Commission [Member]
Commitments and Contingencies [Line Items]
MISO base return on equity, percentage		10.02%	9.88%

Commitments And Contingencies_3

Commitments And Contingencies (Other Purchase Commitments) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,352
Individual commitments incurred	1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	624
Individual commitments incurred	1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	698
Individual commitments incurred	1
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,083
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	494
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	589
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	163
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	79
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	84
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	106
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	51
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	6 Months Ended
	Jun. 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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 912	$ 943	$ 1,990	$ 2,012
Operating income	217	212	439	460
Net income (loss) attributable to common shareowners	160	159	323	351
Net income			323	351
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	487	506	1,037	1,056
Operating income	110	109	206	218
Net income	89	87	161	173
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	402	413	908	909
Operating income	99	95	220	227
Net income	72	63	160	156
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	799	812	1,567	1,586
Operating income	200	195	363	376
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	431	442	819	843
Operating income	105	104	171	179
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	368	370	748	743
Operating income	95	91	192	197
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	77	94	353	356
Operating income	2	8	52	65
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	44	52	194	191
Operating income	0	4	27	36
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	33	42	159	165
Operating income	2	4	25	29
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	13	13	25	23
Operating income	7	1	11	4
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	12	12	24	22
Operating income	5	1	8	3
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1	1	1	1
Operating income	2	0	3	1
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	889	919	1,945	1,965
Operating income	209	204	426	445
Net income (loss) attributable to common shareowners	161	150	321	329
ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	23	24	45	47
Operating income	8	8	13	15
Net income (loss) attributable to common shareowners	$ (1)	$ 9	$ 2	$ 22

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
WPL [Member] | WPL Owed ATC LLC [Member] | Related Party [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 10	$ 10

Related Parties (Service Agreem

Related Parties (Service Agreements) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Corporate Services Billings [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 48	$ 51	$ 88	$ 91
Corporate Services Billings [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	43	42	80	78
Sales Credited [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	1	0	8	0
Sales Credited [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	10	13	22	31
Purchases Billed [Member] | IPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	94	129	187	223
Purchases Billed [Member] | WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 2	$ 39	$ 17	$ 61

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Subsidiary of Common Parent [Member] - Corporate Services [Member] - Related Party [Member] - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
IPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 116	$ 103
WPL [Member]
Related Party Transactions [Line Items]
Net amounts owed	$ 73	$ 56

Related Parties (Amounts Billed

Related Parties (Amounts Billed Between Parties) (Details) - ATC LLC [Member] - WPL [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
ATC Billings To WPL [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 44	$ 35	$ 78	$ 69
WPL Billings To ATC [Member]
Related Party Transactions [Line Items]
Amounts billed between related parties	$ 5	$ 5	$ 11	$ 8