Alliant Energy (LNT) 10-K 24 Feb 23 2022 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Jan. 31, 2023	Jun. 30, 2022
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity Registrant Name	ALLIANT ENERGY CORP
Entity Central Index Key	0000352541
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	4902 N. Biltmore Lane
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53718
City Area Code	608
Local Phone Number	458-3311
Entity File Number	1-9894
Entity Tax Identification Number	39-1380265
Title of 12(b) Security	Common Stock, $0.01 Par Value
Trading Symbol	LNT
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 14,700
Entity Common Stock, Shares Outstanding		251,137,522
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference	Portions of the Proxy Statement relating to Alliant Energy Corporation’s 2023 Annual Meeting of Shareowners are, or will be upon filing with the Securities and Exchange Commission, incorporated by reference into Part III hereof.
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Location	Milwaukee, Wisconsin
Auditor Firm ID	34
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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 Public Float			0
Entity Common Stock, Shares Outstanding		13,370,788
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Location	Milwaukee, Wisconsin
Auditor Firm ID	34
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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 Public Float			$ 0
Entity Common Stock, Shares Outstanding		13,236,601
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Location	Milwaukee, Wisconsin
Auditor Firm ID	34

Consolidated Statements Of Inco

Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Electric utility	$ 3,421	$ 3,081	$ 2,920
Gas utility	642	456	373
Other utility	49	49	49
Non-utility	93	83	74
Total revenues	4,205	3,669	3,416
Operating expenses:
Electric production fuel and purchased power	830	642	652
Electric transmission service	573	537	449
Cost of gas sold	389	258	182
Other operation and maintenance	704	676	670
Depreciation and amortization	671	657	615
Taxes other than income taxes	110	104	108
Total operating expenses	3,277	2,874	2,676
Operating income (loss)	928	795	740
Other (income) and deductions:
Interest expense	325	277	275
Equity income from unconsolidated investments, net	(51)	(62)	(61)
Allowance for funds used during construction	(60)	(25)	(55)
Other	6	5	14
Total other (income) and deductions	220	195	173
Income before income taxes	708	600	567
Income tax expense (benefit)	22	(74)	(57)
Net income	686	674	624
Preferred dividend requirements of Interstate Power and Light Company	0	15	10
Net income attributable to common shareowners	$ 686	$ 659	$ 614
Weighted average number of common shares outstanding:
Basic (in shares)	250.9	250.2	248.4
Diluted (in shares)	251.2	250.7	248.7
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 2.73	$ 2.63	$ 2.47
Diluted (in dollars per share)	$ 2.73	$ 2.63	$ 2.47
IPL [Member]
Revenues:
Electric utility	$ 1,859	$ 1,752	$ 1,695
Gas utility	351	265	208
Other utility	46	46	44
Total revenues	2,256	2,063	1,947
Operating expenses:
Electric production fuel and purchased power	383	295	352
Electric transmission service	407	367	298
Cost of gas sold	206	149	99
Other operation and maintenance	369	362	375
Depreciation and amortization	381	375	356
Taxes other than income taxes	57	55	57
Total operating expenses	1,803	1,603	1,537
Operating income (loss)	453	460	410
Other (income) and deductions:
Interest expense	148	139	139
Allowance for funds used during construction	(11)	(9)	(24)
Other	6	1	8
Total other (income) and deductions	143	131	123
Income before income taxes	310	329	287
Income tax expense (benefit)	(50)	(36)	(47)
Net income	360	365	334
Preferred dividend requirements of Interstate Power and Light Company	0	15	10
Net income attributable to common shareowners	360	350	324
WPL [Member]
Revenues:
Electric utility	1,562	1,329	1,225
Gas utility	291	191	165
Other utility	3	3	5
Total revenues	1,856	1,523	1,395
Operating expenses:
Electric production fuel and purchased power	447	347	300
Electric transmission service	166	170	151
Cost of gas sold	183	109	83
Other operation and maintenance	278	268	254
Depreciation and amortization	283	276	254
Taxes other than income taxes	47	45	47
Total operating expenses	1,404	1,215	1,089
Operating income (loss)	452	308	306
Other (income) and deductions:
Interest expense	121	105	104
Allowance for funds used during construction	(49)	(16)	(31)
Other	(1)	2	3
Total other (income) and deductions	71	91	76
Income before income taxes	381	217	230
Income tax expense (benefit)	66	(51)	(19)
Net income	$ 315	$ 268	$ 249

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 20	$ 39
Accounts receivable, less allowance for expected credit losses	516	440
Production fuel, at weighted average cost	53	51
Gas stored underground, at weighted average cost	132	82
Materials and supplies, at weighted average cost	140	113
Regulatory assets	166	104
Other	223	240
Total current assets	1,250	1,069
Property, plant and equipment, net	16,247	14,987
Investments:
ATC Holdings	358	338
Other	201	179
Total investments	559	517
Other assets:
Regulatory assets	1,880	1,836
Deferred charges and other	227	144
Total other assets	2,107	1,980
Total assets	20,163	18,553
Current liabilities:
Current maturities of long-term debt	408	633
Commercial paper	642	515
Accounts payable	756	436
Regulatory liabilities	206	186
Other	351	284
Total current liabilities	2,363	2,054
Long-term debt, net (excluding current portion)	7,668	6,735
Other liabilities:
Deferred tax liabilities	1,943	1,927
Regulatory liabilities	1,118	1,085
Pension and other benefit obligations	277	374
Other	518	388
Total other liabilities	3,856	3,774
Commitments and contingencies (Note 17)
Common equity:
Common stock	3	3
Additional paid-in capital	2,777	2,749
Retained earnings	3,509	3,250
Shares in deferred compensation trust - 402,134 and 383,532 shares at a weighted average cost of $32.63 and $30.59 per share	(13)	(12)
Total common equity	6,276	5,990
Total liabilities and equity	20,163	18,553
IPL [Member]
Current assets:
Cash and cash equivalents	15	34
Accounts receivable, less allowance for expected credit losses	259	241
Production fuel, at weighted average cost	23	29
Gas stored underground, at weighted average cost	60	40
Materials and supplies, at weighted average cost	83	70
Regulatory assets	85	73
Other	93	77
Total current assets	618	564
Property, plant and equipment, net	8,046	7,983
Other assets:
Regulatory assets	1,301	1,370
Deferred charges and other	110	79
Total other assets	1,411	1,449
Total assets	10,075	9,996
Current liabilities:
Current maturities of long-term debt	0	0
Commercial paper	0	0
Accounts payable	239	173
Accounts payable to associated companies	28	39
Accrued taxes	52	56
Accrued interest	35	36
Regulatory liabilities	114	84
Other	113	67
Total current liabilities	581	455
Long-term debt, net (excluding current portion)	3,646	3,643
Other liabilities:
Deferred tax liabilities	1,047	1,083
Regulatory liabilities	640	607
Pension and other benefit obligations	62	127
Other	291	312
Total other liabilities	2,040	2,129
Commitments and contingencies (Note 17)
Common equity:
Common stock	33	33
Additional paid-in capital	2,807	2,807
Retained earnings	968	929
Total common equity	3,808	3,769
Total liabilities and equity	10,075	9,996
WPL [Member]
Current assets:
Cash and cash equivalents	5	2
Accounts receivable, less allowance for expected credit losses	244	188
Production fuel, at weighted average cost	29	23
Gas stored underground, at weighted average cost	73	42
Materials and supplies, at weighted average cost	54	41
Regulatory assets	81	31
Prepaid gross receipts tax	42	40
Other	60	86
Total current assets	588	453
Property, plant and equipment, net	7,722	6,538
Other assets:
Regulatory assets	579	466
Deferred charges and other	98	61
Total other assets	677	527
Total assets	8,987	7,518
Current liabilities:
Current maturities of long-term debt	0	250
Commercial paper	290	236
Accounts payable	456	190
Regulatory liabilities	92	102
Other	111	112
Total current liabilities	949	890
Long-term debt, net (excluding current portion)	2,770	2,179
Other liabilities:
Deferred tax liabilities	789	753
Regulatory liabilities	478	478
Pension and other benefit obligations	140	159
Other	370	236
Total other liabilities	1,777	1,626
Commitments and contingencies (Note 17)
Common equity:
Common stock	66	66
Additional paid-in capital	2,233	1,704
Retained earnings	1,192	1,053
Total common equity	3,491	2,823
Total liabilities and equity	$ 8,987	$ 7,518

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	251,134,966	250,474,529
Shares in deferred compensation trust (in shares)	402,134	383,532
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 32.63	$ 30.59

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from (used for) operating activities:
Net income	$ 686	$ 674	$ 624
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	671	657	615
Deferred tax expense (benefit) and tax credits	13	(78)	(66)
Other	(18)	17	(2)
Other changes in assets and liabilities:
Accounts receivable	(672)	(530)	(468)
Regulatory assets	(108)	51	(130)
Derivative assets	(61)	(142)	(7)
Accounts payable	78	37	(3)
Regulatory liabilities	22	(66)	(113)
Derivative liabilities	70	(17)	(12)
Deferred income taxes	4	193	171
Pension and other benefit obligations	(97)	(137)	27
DAEC PPA amendment buyout payment	0	0	(110)
Other	(102)	(77)	(25)
Net cash flows from (used for) operating activities	486	582	501
Cash flows from (used for) investing activities:
Utility construction and acquisition expenditures	(1,392)	(1,070)	(1,293)
Other construction and acquisition expenditures	(92)	(99)	(73)
Cash receipts on sold receivables	598	502	458
Other	(47)	(61)	(43)
Net cash flows from (used for) investing activities	(933)	(728)	(951)
Cash flows from (used for) financing activities:
Common stock dividends	(428)	(403)	(377)
Proceeds from issuance of common stock, net	25	28	247
Payments to redeem cumulative preferred stock of IPL	0	(200)	0
Proceeds from issuance of long-term debt	1,338	600	1,250
Payments to retire long-term debt	(633)	(8)	(657)
Net change in commercial paper	127	126	52
Contributions from noncontrolling interest	29	0	0
Distributions to noncontrolling interest	(29)	0	0
Other	2	(13)	(27)
Net cash flows from (used for) financing activities	431	130	488
Net increase (decrease) in cash, cash equivalents and restricted cash	(16)	(16)	38
Cash, cash equivalents and restricted cash at beginning of period	40	56	18
Cash, cash equivalents and restricted cash at end of period	24	40	56
Supplemental cash flows information:
Interest	(311)	(272)	(274)
Income taxes, net	(6)	(3)	5
Significant non-cash investing and financing activities:
Accrued capital expenditures	382	141	131
Beneficial interest obtained in exchange for securitized accounts receivable	185	214	188
IPL [Member]
Cash flows from (used for) operating activities:
Net income	360	365	334
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	381	375	356
Deferred tax expense (benefit) and tax credits	(13)	(14)	(52)
Equity component of allowance for funds used during construction	(8)	(7)	(17)
Other	0	11	12
Other changes in assets and liabilities:
Accounts receivable	(611)	(539)	(466)
Regulatory assets	56	30	(93)
Derivative assets	(54)	(55)	(7)
Gas stored underground	(20)	(20)	2
Accounts payable	65	15	6
Regulatory liabilities	53	1	(20)
Derivative liabilities	42	(8)	(5)
Deferred income taxes	(24)	62	79
Pension and other benefit obligations	(65)	(59)	18
DAEC PPA amendment buyout payment	0	0	(110)
Other	(79)	(4)	(43)
Net cash flows from (used for) operating activities	83	153	(6)
Cash flows from (used for) investing activities:
Utility construction and acquisition expenditures	(372)	(384)	(687)
Cash receipts on sold receivables	598	502	458
Other	(11)	(27)	(72)
Net cash flows from (used for) investing activities	215	91	(301)
Cash flows from (used for) financing activities:
Common stock dividends	(321)	(400)	(236)
Capital contributions from parent	0	50	404
Payments to redeem cumulative preferred stock of IPL	0	(200)	0
Proceeds from issuance of long-term debt	0	300	400
Payments to retire long-term debt	0	0	(200)
Other	4	(10)	(20)
Net cash flows from (used for) financing activities	(317)	(260)	348
Net increase (decrease) in cash, cash equivalents and restricted cash	(19)	(16)	41
Cash, cash equivalents and restricted cash at beginning of period	34	50	9
Cash, cash equivalents and restricted cash at end of period	15	34	50
Supplemental cash flows information:
Interest	(148)	(138)	(141)
Income taxes, net	36	47	(18)
Significant non-cash investing and financing activities:
Accrued capital expenditures	56	57	73
Beneficial interest obtained in exchange for securitized accounts receivable	185	214	188
WPL [Member]
Cash flows from (used for) operating activities:
Net income	315	268	249
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	283	276	254
Deferred tax expense (benefit) and tax credits	4	(79)	(15)
Other	(15)	11	2
Other changes in assets and liabilities:
Accounts receivable	(53)	3	(1)
Regulatory assets	(163)	21	(37)
Derivative assets	(7)	(87)	0
Regulatory liabilities	(31)	(67)	(93)
Deferred income taxes	32	132	90
Pension and other benefit obligations	(19)	(63)	11
Other	(47)	(44)	6
Net cash flows from (used for) operating activities	299	371	466
Cash flows from (used for) investing activities:
Utility construction and acquisition expenditures	(1,020)	(686)	(606)
Other	(13)	(30)	(7)
Net cash flows from (used for) investing activities	(1,033)	(716)	(613)
Cash flows from (used for) financing activities:
Common stock dividends	(176)	(168)	(160)
Capital contributions from parent	530	245	25
Proceeds from issuance of long-term debt	588	300	350
Payments to retire long-term debt	(250)	0	(150)
Net change in commercial paper	54	(21)	89
Contributions from noncontrolling interest	29	0	0
Distributions to noncontrolling interest	(29)	0	0
Other	(9)	(12)	(8)
Net cash flows from (used for) financing activities	737	344	146
Net increase (decrease) in cash, cash equivalents and restricted cash	3	(1)	(1)
Cash, cash equivalents and restricted cash at beginning of period	2	3	4
Cash, cash equivalents and restricted cash at end of period	5	2	3
Supplemental cash flows information:
Interest	(111)	(101)	(102)
Income taxes, net	(56)	(38)	13
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 319	$ 81	$ 55

Consolidated Statements of Comm

Consolidated Statements of Common Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	IPL [Member]	WPL [Member]	Common Stock [Member]	Common Stock [Member] IPL [Member]	Common Stock [Member] WPL [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] IPL [Member]	Additional Paid-in Capital [Member] WPL [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings [Member] IPL [Member]	Retained Earnings [Member] WPL [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Shares in Deferred Compensation Trust [Member]	Cumulative Preferred Stock [Member]	Cumulative Preferred Stock [Member] IPL [Member]	Noncontrolling Interest [Member]	Noncontrolling Interest [Member] WPL [Member]
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Retained earnings		$ (9)										$ (9)
Beginning balance at Dec. 31, 2019					$ 2	$ 33	$ 66	$ 2,446	$ 2,348	$ 1,434	$ 2,766		$ 891	$ 864	$ 1	$ (10)	$ 200	$ 200	$ 0	$ 0
Beginning balance at Dec. 31, 2019	$ 5,405		$ 3,472	$ 2,364
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Net income attributable to common shareowners	614		324								614		324
Net income	624		334	249										249
Common stock dividends	(377)		(236)	(160)							(377)		(236)	(160)
Equity forward settlements and Shareowner Direct Plan issuances	247							247
Capital contributions from parent			404	25					404	25
Equity-based compensation plans and other	10							11								(1)
Contributions from noncontrolling interest	0			0
Distributions to noncontrolling interest	0			0
Payments to redeem cumulative preferred stock of IPL	0		0
Other comprehensive income (loss), net of tax	(2)														(2)
Ending balance at Dec. 31, 2020					2	33	66	2,704	2,752	1,459	2,994		979	953	(1)	(11)	200	200	0	0
Ending balance at Dec. 31, 2020	5,888		3,964	2,478
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Retained earnings		$ (9)
Net income attributable to common shareowners	659		350								659		350
Net income	674		365	268										268
Common stock dividends	(403)		(400)	(168)							(403)		(400)	(168)
Equity forward settlements and Shareowner Direct Plan issuances	28				1			27
Capital contributions from parent			50	245					50	245
Equity-based compensation plans and other	17		5					18	5							(1)
Contributions from noncontrolling interest	0			0
Distributions to noncontrolling interest	0			0
Payments to redeem cumulative preferred stock of IPL	(200)		(200)														(200)	(200)
Other comprehensive income (loss), net of tax	1														1
Ending balance at Dec. 31, 2021	5,990		3,769	2,823	3	33	66	2,749	2,807	1,704	3,250		929	1,053	0	(12)	0	0	0	0
Ending balance at Dec. 31, 2021	5,990		3,769	2,823
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Retained earnings	3,250		929	1,053
Net income attributable to common shareowners	686		360								686		360
Net income	686		360	315										315
Common stock dividends	(428)		(321)	(176)							(428)		(321)	(176)
Equity forward settlements and Shareowner Direct Plan issuances	25							25
Capital contributions from parent			0	530						530
Equity-based compensation plans and other	3			(1)				3		(1)	1					(1)
Contributions from noncontrolling interest	29			29															29	29
Distributions to noncontrolling interest	(29)			(29)															(29)	(29)
Payments to redeem cumulative preferred stock of IPL	0		0
Ending balance at Dec. 31, 2022	6,276		3,808	3,491	$ 3	$ 33	$ 66	$ 2,777	$ 2,807	$ 2,233	$ 3,509		$ 968	$ 1,192	$ 0	$ (13)	$ 0	$ 0	$ 0	$ 0
Ending balance at Dec. 31, 2022	6,276		3,808	3,491
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Retained earnings	$ 3,509		$ 968	$ 1,192

Consolidated Statements of Co_2

Consolidated Statements of Common Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Stockholders' Equity [Abstract]
Common stock dividends (in dollars per share)	$ 1.71	$ 1.61	$ 1.52

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES(a) General - Description of Business - Alliant Energy’s financial statements include the accounts of Alliant Energy and its consolidated subsidiaries. Alliant Energy is a Midwest U.S. energy holding company, whose primary wholly-owned subsidiaries are IPL, WPL, AEF and Corporate Services. IPL’s financial statements include the accounts of IPL and its consolidated subsidiaries, including IPL SPE LLC, which is used for IPL’s sales of accounts receivable program. IPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa. IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa, and is engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa. WPL’s financial statements include the accounts of WPL and its consolidated subsidiaries. WPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin. WPL also sells electricity to wholesale customers in Wisconsin. AEF is comprised of Travero, ATI, corporate venture investments, a non-utility wind farm, the Sheboygan Falls Energy Facility and other non-utility holdings. Travero includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. ATI, a wholly-owned subsidiary of AEF, holds all of Alliant Energy’s interest in ATC Holdings. Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy. The non-utility wind farm includes a 50% cash equity ownership interest in a 225 MW wind farm located in Oklahoma. The Sheboygan Falls Energy Facility is a 347 MW, simple-cycle, natural gas-fired EGU near Sheboygan Falls, Wisconsin, which is leased to WPL for an initial period of 20 years ending in 2025. Corporate Services is the subsidiary formed to provide administrative services to Alliant Energy and its subsidiaries. Basis of Presentation - The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method. All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes. The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Use of Estimates - The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Federal Tax Reform repealed corporate federal alternative minimum tax and allowed unutilized alternative minimum tax credits to be refunded over four tax years beginning with the U.S. federal tax return for calendar year 2018. Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, Alliant Energy received the remaining alternative minimum tax credits refunds in 2020. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the modified separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). The difference in the income taxes recorded for IPL and WPL under the modified separate return method compared to the income taxes recorded on a separate return basis was not material in 2022, 2021 and 2020. Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023. AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3% In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements. Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the end of each customer’s last billing period. The unbilled component is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2022, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed. Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement. Refer to Note 2 for discussion of the recognition of regulatory assets and regulatory liabilities related to the unrealized losses and gains on derivative instruments. Refer to Notes 15 , 16 and 17(f) for further discussion of derivatives and related credit risk. Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value. In 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables, certain other assets and off-balance sheet credit exposures. Alliant Energy, IPL and WPL adopted this standard on January 1, 2020 using a modified retrospective method of adoption, which required cumulative effect adjustments to retained earnings on January 1, 2020. IPL and WPL did not record a cumulative effect adjustment to retained earnings and Alliant Energy recorded a pre-tax $12 million (after-tax $9 million) cumulative effect adjustment to decrease retained earnings related to Alliant Energy’s guarantees in the partnership obligations of an affiliate of Whiting Petroleum (refer to Note 17(d) for further discussion). This adjustment is included in “Adoption of new accounting standard” in Alliant Energy’s equity statement for 2020.
IPL [Member]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES(a) General - Description of Business - Alliant Energy’s financial statements include the accounts of Alliant Energy and its consolidated subsidiaries. Alliant Energy is a Midwest U.S. energy holding company, whose primary wholly-owned subsidiaries are IPL, WPL, AEF and Corporate Services. IPL’s financial statements include the accounts of IPL and its consolidated subsidiaries, including IPL SPE LLC, which is used for IPL’s sales of accounts receivable program. IPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa. IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa, and is engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa. WPL’s financial statements include the accounts of WPL and its consolidated subsidiaries. WPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin. WPL also sells electricity to wholesale customers in Wisconsin. AEF is comprised of Travero, ATI, corporate venture investments, a non-utility wind farm, the Sheboygan Falls Energy Facility and other non-utility holdings. Travero includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. ATI, a wholly-owned subsidiary of AEF, holds all of Alliant Energy’s interest in ATC Holdings. Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy. The non-utility wind farm includes a 50% cash equity ownership interest in a 225 MW wind farm located in Oklahoma. The Sheboygan Falls Energy Facility is a 347 MW, simple-cycle, natural gas-fired EGU near Sheboygan Falls, Wisconsin, which is leased to WPL for an initial period of 20 years ending in 2025. Corporate Services is the subsidiary formed to provide administrative services to Alliant Energy and its subsidiaries. Basis of Presentation - The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method. All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes. The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Use of Estimates - The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Federal Tax Reform repealed corporate federal alternative minimum tax and allowed unutilized alternative minimum tax credits to be refunded over four tax years beginning with the U.S. federal tax return for calendar year 2018. Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, Alliant Energy received the remaining alternative minimum tax credits refunds in 2020. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the modified separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). The difference in the income taxes recorded for IPL and WPL under the modified separate return method compared to the income taxes recorded on a separate return basis was not material in 2022, 2021 and 2020. Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023. AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3% In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements. Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the end of each customer’s last billing period. The unbilled component is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2022, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed. Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement. Refer to Note 2 for discussion of the recognition of regulatory assets and regulatory liabilities related to the unrealized losses and gains on derivative instruments. Refer to Notes 15 , 16 and 17(f) for further discussion of derivatives and related credit risk. Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value. In 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables, certain other assets and off-balance sheet credit exposures. Alliant Energy, IPL and WPL adopted this standard on January 1, 2020 using a modified retrospective method of adoption, which required cumulative effect adjustments to retained earnings on January 1, 2020. IPL and WPL did not record a cumulative effect adjustment to retained earnings and Alliant Energy recorded a pre-tax $12 million (after-tax $9 million) cumulative effect adjustment to decrease retained earnings related to Alliant Energy’s guarantees in the partnership obligations of an affiliate of Whiting Petroleum (refer to Note 17(d) for further discussion). This adjustment is included in “Adoption of new accounting standard” in Alliant Energy’s equity statement for 2020.
WPL [Member]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES(a) General - Description of Business - Alliant Energy’s financial statements include the accounts of Alliant Energy and its consolidated subsidiaries. Alliant Energy is a Midwest U.S. energy holding company, whose primary wholly-owned subsidiaries are IPL, WPL, AEF and Corporate Services. IPL’s financial statements include the accounts of IPL and its consolidated subsidiaries, including IPL SPE LLC, which is used for IPL’s sales of accounts receivable program. IPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa. IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa, and is engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa. WPL’s financial statements include the accounts of WPL and its consolidated subsidiaries. WPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin. WPL also sells electricity to wholesale customers in Wisconsin. AEF is comprised of Travero, ATI, corporate venture investments, a non-utility wind farm, the Sheboygan Falls Energy Facility and other non-utility holdings. Travero includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. ATI, a wholly-owned subsidiary of AEF, holds all of Alliant Energy’s interest in ATC Holdings. Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy. The non-utility wind farm includes a 50% cash equity ownership interest in a 225 MW wind farm located in Oklahoma. The Sheboygan Falls Energy Facility is a 347 MW, simple-cycle, natural gas-fired EGU near Sheboygan Falls, Wisconsin, which is leased to WPL for an initial period of 20 years ending in 2025. Corporate Services is the subsidiary formed to provide administrative services to Alliant Energy and its subsidiaries. Basis of Presentation - The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method. All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes. The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes. Use of Estimates - The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Federal Tax Reform repealed corporate federal alternative minimum tax and allowed unutilized alternative minimum tax credits to be refunded over four tax years beginning with the U.S. federal tax return for calendar year 2018. Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, Alliant Energy received the remaining alternative minimum tax credits refunds in 2020. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the modified separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). The difference in the income taxes recorded for IPL and WPL under the modified separate return method compared to the income taxes recorded on a separate return basis was not material in 2022, 2021 and 2020. Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023. AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3% In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements. Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the end of each customer’s last billing period. The unbilled component is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2022, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed. Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement. Refer to Note 2 for discussion of the recognition of regulatory assets and regulatory liabilities related to the unrealized losses and gains on derivative instruments. Refer to Notes 15 , 16 and 17(f) for further discussion of derivatives and related credit risk. Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value. In 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables, certain other assets and off-balance sheet credit exposures. Alliant Energy, IPL and WPL adopted this standard on January 1, 2020 using a modified retrospective method of adoption, which required cumulative effect adjustments to retained earnings on January 1, 2020. IPL and WPL did not record a cumulative effect adjustment to retained earnings and Alliant Energy recorded a pre-tax $12 million (after-tax $9 million) cumulative effect adjustment to decrease retained earnings related to Alliant Energy’s guarantees in the partnership obligations of an affiliate of Whiting Petroleum (refer to Note 17(d) for further discussion). This adjustment is included in “Adoption of new accounting standard” in Alliant Energy’s equity statement for 2020.

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2022
Regulatory Matters [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets - Alliant Energy, IPL and WPL assess whether IPL’s and WPL’s regulatory assets are probable of future recovery by considering factors such as applicable regulations, recent orders by the applicable regulatory agencies, historical treatment of similar costs by the applicable regulatory agencies and regulatory environment changes. Based on these assessments, Alliant Energy, IPL and WPL believe the regulatory assets recognized as of December 31, 2022 are probable of future recovery. However, no assurance can be made that IPL and WPL will recover all of these regulatory assets in future rates. If future recovery of a regulatory asset ceases to be probable, the regulatory asset will be charged to expense. At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $929 $934 $848 $884 $81 $50 Pension and OPEB costs 392 462 197 228 195 234 Commodity cost recovery 160 42 1 2 159 40 AROs 151 128 110 89 41 39 Derivatives 84 8 48 4 36 4 Assets retired early 70 92 53 66 17 26 IPL’s DAEC PPA amendment 66 90 66 90 — — WPL’s Western Wisconsin gas distribution expansion investments 48 52 — — 48 52 Other 146 132 63 80 83 52 $2,046 $1,940 $1,386 $1,443 $660 $497 At December 31, 2022, IPL and WPL had $66 million and $28 million, respectively, of regulatory assets that were not earning a return on investment. IPL’s regulatory assets that were not earning a return consisted primarily of retired analog electric meters, emission allowances and costs for certain construction projects. WPL’s regulatory assets that were not earning a return consisted primarily of amounts related to the wholesale portion of under-collected costs, and costs for future expansion projects. The other regulatory assets reported in the above table either earn a return or the cash has not yet been expended, in which case the assets are offset by liabilities that also do not incur a carrying cost. Tax-related - IPL and WPL record regulatory assets for certain temporary differences (primarily related to utility property, plant and equipment at IPL) that result in a decrease in current rates charged to customers and an increase in future rates charged to customers based on the timing of income tax expense that is used to determine such rates. These temporary differences for IPL include the impacts of qualifying deductions for repairs expenditures, allocation of mixed service costs, and Iowa accelerated tax depreciation, which all contribute to lower current income tax expense during the first part of an asset’s useful life and higher current income tax expense during the latter part of an asset’s useful life. These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates. Refer to Note 12 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in 2022. Pension and other postretirement benefits costs - The IUB, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates. These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs. Regulatory assets are also increased or decreased as a result of the annual defined benefit plan measurement process. Pension and OPEB costs are included within the recoverable cost of service component of rates charged to IPL’s and WPL’s retail and wholesale customers, which are based upon pension and OPEB costs determined in accordance with GAAP and are calculated in accordance with IPL’s and WPL’s respective regulatory jurisdictions. Commodity cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s commodity cost recovery mechanisms. The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. In 2021, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $37 million deferral as of December 31, 2022, which will be collected in 2023 from its retail electric customers, plus interest. In 2022, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $117 million deferral as of December 31, 2022, which is currently expected to be addressed in WPL’s next retail electric rate review. AROs - Alliant Energy, IPL and WPL believe it is probable that certain differences between expenses accrued for AROs related to their utility operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets. Derivatives - In accordance with IPL’s and WPL’s fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recoverable from customers in the future after any losses are realized, and gains from derivative instruments are refundable to customers in the future after any gains are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Refer to Note 15 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during 2022, which result in comparable changes to regulatory assets/liabilities on the balance sheets. Assets retired early - IPL and WPL have retired various natural gas- and coal-fired EGUs, and IPL has retired certain analog electric meters. As a result, the remaining net book value of these assets was reclassified from property, plant and equipment to a regulatory asset on their respective balance sheets. Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2022 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $16 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 13 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 24 Return of remaining net book value through 2028 IUB and FERC WPL Edgewater Unit 4 2018 17 Return of and return on remaining net book value through 2028 PSCW and FERC IPL’s DAEC PPA Amendment - In 2020, IPL made a buyout payment of $110 million in exchange for shortening the term of its DAEC PPA by 5 years. The payment was included in “DAEC PPA amendment buyout payment” in Alliant Energy’s and IPL’s cash flows used for operating activities in 2020. The buyout payment, including a return on, will be recovered from IPL’s retail and wholesale customers from 2021 through the end of 2025, and is currently being amortized to “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. WPL’s Western Wisconsin gas distribution expansion investments - WPL made contributions in aid of construction to a third party for investments as part of its Western Wisconsin gas distribution expansion project. Pursuant to authorization by the PSCW, Alliant Energy and WPL have recorded a regulatory asset for these costs, and are authorized by the PSCW to recover these amounts from WPL’s retail gas customers in base rates from 2021 through the end of 2040. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $579 $585 $303 $312 $276 $273 Cost of removal obligations 398 384 259 252 139 132 Derivatives 210 166 115 77 95 89 Commodity cost recovery 40 17 38 15 2 2 WPL’s West Riverside liquidated damages 32 36 — — 32 36 Electric transmission cost recovery 20 51 10 27 10 24 Other 45 32 29 8 16 24 $1,324 $1,271 $754 $691 $570 $580 Tax-related regulatory liabilities reduce revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings. Cost of removal obligations, to the extent expensed through depreciation rates, reduce rate base. A significant portion of the remaining regulatory liabilities is not used to adjust revenue requirement calculations. Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform. The majority of these benefits related to accelerated depreciation are subject to tax normalization rules. These rules limit the rate at which these tax benefits are allowed to be passed on to customers. Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated AROs or that have removal costs in addition to AROs. Alliant Energy, IPL and WPL record a regulatory liability for the amounts collected in rates for these future removal costs and reduce the regulatory liability for amounts spent on removal activities. Cash payments related to cost of removal obligations are included in “Other” in cash flows used for investing activities. WPL’s West Riverside liquidated damages - Pursuant to terms included in the related West Riverside construction procurement contracts, WPL reached agreement with the contractor on liquidated damages in 2020. A significant portion of the liquidated damages was settled by WPL offsetting amounts owed to the contractor that were previously withheld for payment, which were non-cash investing activities. In 2020, the PSCW authorized WPL to record the liquidated damages as a regulatory liability, which the PSCW authorized to be returned to WPL’s retail customers in 2022 and 2023, resulting 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 in 2022. Electric transmission cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s electric transmission cost recovery mechanisms. In 2020, pursuant to an IUB order, IPL issued $42 million of credits to its retail electric customers through its transmission cost rider for amounts previously collected in rates, which resulted in a reduction to “Electric transmission service” expense in Alliant Energy’s and IPL’s income statements in 2020. Derecho Windstorm - In August 2020, a derecho windstorm caused considerable damage to IPL’s electric distribution system in its service territory, and over 250,000 of its customers lost power. IPL completed its initial restoration and rebuilding efforts in August 2020. As of December 31, 2022, approximately $140 million of costs from the windstorm were recorded substantially to “Property, plant and equipment, net” on Alliant Energy’s and IPL’s balance sheets. In December 2020, IPL received approval from the IUB for utilization of a regulatory account to track certain incremental costs and benefits incurred resulting from the windstorm. These incremental costs and benefits were not addressed in the IUB’s order for IPL’s 2020 forward-looking Test Period electric subsequent proceeding, and are expected to be addressed in future regulatory proceedings. Tax benefits and the incremental operation and maintenance expenses resulting from the windstorm were deferred and recorded as a net regulatory liability of $8 million as of December 31, 2022, which is included in “Other” regulatory liabilities in the above table. Rate Reviews - IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million, on an annual basis, was implemented effective April 1, 2019. In October 2019, IPL reached a settlement agreement with certain stakeholders for an annual retail electric base rate increase of $127 million. In January 2020, the IUB issued an order approving the settlement with final rates, which were effective February 26, 2020. The agreement includes both the recovery of and a return on IPL’s early retired EGUs, and the recovery of IPL’s retired analog electric meters. In addition, as discussed in Note 1(g) , the net impact of certain costs and benefits resulting from IPL’s 1,000 MW expansion of wind generation in 2019 and 2020 is being recovered from its retail electric customers through the renewable energy rider. The agreement also includes IPL providing retail electric billing credits, which began in the third quarter of 2020 through June 2021, and in aggregate include $27 million of excess deferred tax benefits and $8 million from a partial refund of interim rates implemented in 2019. In 2021, the IUB issued an order for IPL’s 2020 forward-looking Test Period electric subsequent proceeding, which compared actual revenues and costs to those initially forecasted by IPL, and authorized IPL to maintain its current retail electric rates. IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers based on a 2020 forward-looking Test Period. In October 2019, IPL reached a settlement agreement with certain stakeholders for an annual retail gas base rate increase of $12 million. In December 2019, the IUB issued an order approving the settlement with final rates, which were effective January 10, 2020. In 2021, the IUB issued an order for IPL’s 2020 forward-looking Test Period gas subsequent proceeding, which compared actual revenues and costs to those initially forecasted by IPL, and authorized IPL to maintain its current retail gas rates. WPL’s Retail Electric and Gas Rate Review (2019/2020 Forward-looking Test Period) - In December 2018, the PSCW issued an order approving WPL’s proposed settlement for its retail electric and gas rate review covering the 2019/2020 Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. Under the settlement, WPL retail electric and gas base rates did not change from then current levels through the end of 2020. In September 2020, pursuant to an August 2020 PSCW order, WPL refunded $12 million of 2019 fuel-related cost over-collections to its retail electric customers. In addition, WPL’s amortization of excess deferred taxes resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform was used to offset increases in WPL’s 2020 increased revenue requirements. WPL’s Retail Electric and Gas Rate Review (2021 Forward-looking Test Period) - In December 2020, the PSCW issued an order authorizing WPL to maintain its then current retail electric and gas base rates, authorized return on common equity, regulatory capital structure and earnings sharing mechanism through the end of 2021. WPL utilized anticipated fuel-related cost savings and excess deferred income tax benefits in 2021 to offset the revenue requirement impacts of increasing electric and gas rate base, including the Kossuth wind farm, which was placed in service in October 2020, and the expansion of its gas distribution system in Western Wisconsin, which was placed in service in November 2020. WPL’s Retail Electric and Gas Rate Reviews (2022/2023 Forward-looking Test Period) - In December 2021, the PSCW issued an order authorizing annual base rate increases of $114 million and $15 million for WPL’s retail electric and gas customers, respectively, covering the 2022/2023 forward-looking Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. The key drivers for the annual base rate increases include higher retail fuel-related costs in 2022, lower excess deferred income tax benefits in 2022 and 2023 and revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation. In addition, the PSCW authorized WPL to receive a recovery of and a return on the remaining net book value of Edgewater Unit 5 through 2023. Retail electric rate changes were effective on January 1, 2022 and extend through the end of 2023. Retail gas rate changes were effective on January 1, 2022 and extended through the end of 2022.
IPL [Member]
Regulatory Matters [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets - Alliant Energy, IPL and WPL assess whether IPL’s and WPL’s regulatory assets are probable of future recovery by considering factors such as applicable regulations, recent orders by the applicable regulatory agencies, historical treatment of similar costs by the applicable regulatory agencies and regulatory environment changes. Based on these assessments, Alliant Energy, IPL and WPL believe the regulatory assets recognized as of December 31, 2022 are probable of future recovery. However, no assurance can be made that IPL and WPL will recover all of these regulatory assets in future rates. If future recovery of a regulatory asset ceases to be probable, the regulatory asset will be charged to expense. At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $929 $934 $848 $884 $81 $50 Pension and OPEB costs 392 462 197 228 195 234 Commodity cost recovery 160 42 1 2 159 40 AROs 151 128 110 89 41 39 Derivatives 84 8 48 4 36 4 Assets retired early 70 92 53 66 17 26 IPL’s DAEC PPA amendment 66 90 66 90 — — WPL’s Western Wisconsin gas distribution expansion investments 48 52 — — 48 52 Other 146 132 63 80 83 52 $2,046 $1,940 $1,386 $1,443 $660 $497 At December 31, 2022, IPL and WPL had $66 million and $28 million, respectively, of regulatory assets that were not earning a return on investment. IPL’s regulatory assets that were not earning a return consisted primarily of retired analog electric meters, emission allowances and costs for certain construction projects. WPL’s regulatory assets that were not earning a return consisted primarily of amounts related to the wholesale portion of under-collected costs, and costs for future expansion projects. The other regulatory assets reported in the above table either earn a return or the cash has not yet been expended, in which case the assets are offset by liabilities that also do not incur a carrying cost. Tax-related - IPL and WPL record regulatory assets for certain temporary differences (primarily related to utility property, plant and equipment at IPL) that result in a decrease in current rates charged to customers and an increase in future rates charged to customers based on the timing of income tax expense that is used to determine such rates. These temporary differences for IPL include the impacts of qualifying deductions for repairs expenditures, allocation of mixed service costs, and Iowa accelerated tax depreciation, which all contribute to lower current income tax expense during the first part of an asset’s useful life and higher current income tax expense during the latter part of an asset’s useful life. These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates. Refer to Note 12 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in 2022. Pension and other postretirement benefits costs - The IUB, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates. These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs. Regulatory assets are also increased or decreased as a result of the annual defined benefit plan measurement process. Pension and OPEB costs are included within the recoverable cost of service component of rates charged to IPL’s and WPL’s retail and wholesale customers, which are based upon pension and OPEB costs determined in accordance with GAAP and are calculated in accordance with IPL’s and WPL’s respective regulatory jurisdictions. Commodity cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s commodity cost recovery mechanisms. The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. In 2021, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $37 million deferral as of December 31, 2022, which will be collected in 2023 from its retail electric customers, plus interest. In 2022, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $117 million deferral as of December 31, 2022, which is currently expected to be addressed in WPL’s next retail electric rate review. AROs - Alliant Energy, IPL and WPL believe it is probable that certain differences between expenses accrued for AROs related to their utility operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets. Derivatives - In accordance with IPL’s and WPL’s fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recoverable from customers in the future after any losses are realized, and gains from derivative instruments are refundable to customers in the future after any gains are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Refer to Note 15 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during 2022, which result in comparable changes to regulatory assets/liabilities on the balance sheets. Assets retired early - IPL and WPL have retired various natural gas- and coal-fired EGUs, and IPL has retired certain analog electric meters. As a result, the remaining net book value of these assets was reclassified from property, plant and equipment to a regulatory asset on their respective balance sheets. Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2022 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $16 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 13 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 24 Return of remaining net book value through 2028 IUB and FERC WPL Edgewater Unit 4 2018 17 Return of and return on remaining net book value through 2028 PSCW and FERC IPL’s DAEC PPA Amendment - In 2020, IPL made a buyout payment of $110 million in exchange for shortening the term of its DAEC PPA by 5 years. The payment was included in “DAEC PPA amendment buyout payment” in Alliant Energy’s and IPL’s cash flows used for operating activities in 2020. The buyout payment, including a return on, will be recovered from IPL’s retail and wholesale customers from 2021 through the end of 2025, and is currently being amortized to “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. WPL’s Western Wisconsin gas distribution expansion investments - WPL made contributions in aid of construction to a third party for investments as part of its Western Wisconsin gas distribution expansion project. Pursuant to authorization by the PSCW, Alliant Energy and WPL have recorded a regulatory asset for these costs, and are authorized by the PSCW to recover these amounts from WPL’s retail gas customers in base rates from 2021 through the end of 2040. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $579 $585 $303 $312 $276 $273 Cost of removal obligations 398 384 259 252 139 132 Derivatives 210 166 115 77 95 89 Commodity cost recovery 40 17 38 15 2 2 WPL’s West Riverside liquidated damages 32 36 — — 32 36 Electric transmission cost recovery 20 51 10 27 10 24 Other 45 32 29 8 16 24 $1,324 $1,271 $754 $691 $570 $580 Tax-related regulatory liabilities reduce revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings. Cost of removal obligations, to the extent expensed through depreciation rates, reduce rate base. A significant portion of the remaining regulatory liabilities is not used to adjust revenue requirement calculations. Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform. The majority of these benefits related to accelerated depreciation are subject to tax normalization rules. These rules limit the rate at which these tax benefits are allowed to be passed on to customers. Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated AROs or that have removal costs in addition to AROs. Alliant Energy, IPL and WPL record a regulatory liability for the amounts collected in rates for these future removal costs and reduce the regulatory liability for amounts spent on removal activities. Cash payments related to cost of removal obligations are included in “Other” in cash flows used for investing activities. WPL’s West Riverside liquidated damages - Pursuant to terms included in the related West Riverside construction procurement contracts, WPL reached agreement with the contractor on liquidated damages in 2020. A significant portion of the liquidated damages was settled by WPL offsetting amounts owed to the contractor that were previously withheld for payment, which were non-cash investing activities. In 2020, the PSCW authorized WPL to record the liquidated damages as a regulatory liability, which the PSCW authorized to be returned to WPL’s retail customers in 2022 and 2023, resulting 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 in 2022. Electric transmission cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s electric transmission cost recovery mechanisms. In 2020, pursuant to an IUB order, IPL issued $42 million of credits to its retail electric customers through its transmission cost rider for amounts previously collected in rates, which resulted in a reduction to “Electric transmission service” expense in Alliant Energy’s and IPL’s income statements in 2020. Derecho Windstorm - In August 2020, a derecho windstorm caused considerable damage to IPL’s electric distribution system in its service territory, and over 250,000 of its customers lost power. IPL completed its initial restoration and rebuilding efforts in August 2020. As of December 31, 2022, approximately $140 million of costs from the windstorm were recorded substantially to “Property, plant and equipment, net” on Alliant Energy’s and IPL’s balance sheets. In December 2020, IPL received approval from the IUB for utilization of a regulatory account to track certain incremental costs and benefits incurred resulting from the windstorm. These incremental costs and benefits were not addressed in the IUB’s order for IPL’s 2020 forward-looking Test Period electric subsequent proceeding, and are expected to be addressed in future regulatory proceedings. Tax benefits and the incremental operation and maintenance expenses resulting from the windstorm were deferred and recorded as a net regulatory liability of $8 million as of December 31, 2022, which is included in “Other” regulatory liabilities in the above table. Rate Reviews - IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million, on an annual basis, was implemented effective April 1, 2019. In October 2019, IPL reached a settlement agreement with certain stakeholders for an annual retail electric base rate increase of $127 million. In January 2020, the IUB issued an order approving the settlement with final rates, which were effective February 26, 2020. The agreement includes both the recovery of and a return on IPL’s early retired EGUs, and the recovery of IPL’s retired analog electric meters. In addition, as discussed in Note 1(g) , the net impact of certain costs and benefits resulting from IPL’s 1,000 MW expansion of wind generation in 2019 and 2020 is being recovered from its retail electric customers through the renewable energy rider. The agreement also includes IPL providing retail electric billing credits, which began in the third quarter of 2020 through June 2021, and in aggregate include $27 million of excess deferred tax benefits and $8 million from a partial refund of interim rates implemented in 2019. In 2021, the IUB issued an order for IPL’s 2020 forward-looking Test Period electric subsequent proceeding, which compared actual revenues and costs to those initially forecasted by IPL, and authorized IPL to maintain its current retail electric rates. IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers based on a 2020 forward-looking Test Period. In October 2019, IPL reached a settlement agreement with certain stakeholders for an annual retail gas base rate increase of $12 million. In December 2019, the IUB issued an order approving the settlement with final rates, which were effective January 10, 2020. In 2021, the IUB issued an order for IPL’s 2020 forward-looking Test Period gas subsequent proceeding, which compared actual revenues and costs to those initially forecasted by IPL, and authorized IPL to maintain its current retail gas rates. WPL’s Retail Electric and Gas Rate Review (2019/2020 Forward-looking Test Period) - In December 2018, the PSCW issued an order approving WPL’s proposed settlement for its retail electric and gas rate review covering the 2019/2020 Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. Under the settlement, WPL retail electric and gas base rates did not change from then current levels through the end of 2020. In September 2020, pursuant to an August 2020 PSCW order, WPL refunded $12 million of 2019 fuel-related cost over-collections to its retail electric customers. In addition, WPL’s amortization of excess deferred taxes resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform was used to offset increases in WPL’s 2020 increased revenue requirements. WPL’s Retail Electric and Gas Rate Review (2021 Forward-looking Test Period) - In December 2020, the PSCW issued an order authorizing WPL to maintain its then current retail electric and gas base rates, authorized return on common equity, regulatory capital structure and earnings sharing mechanism through the end of 2021. WPL utilized anticipated fuel-related cost savings and excess deferred income tax benefits in 2021 to offset the revenue requirement impacts of increasing electric and gas rate base, including the Kossuth wind farm, which was placed in service in October 2020, and the expansion of its gas distribution system in Western Wisconsin, which was placed in service in November 2020. WPL’s Retail Electric and Gas Rate Reviews (2022/2023 Forward-looking Test Period) - In December 2021, the PSCW issued an order authorizing annual base rate increases of $114 million and $15 million for WPL’s retail electric and gas customers, respectively, covering the 2022/2023 forward-looking Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. The key drivers for the annual base rate increases include higher retail fuel-related costs in 2022, lower excess deferred income tax benefits in 2022 and 2023 and revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation. In addition, the PSCW authorized WPL to receive a recovery of and a return on the remaining net book value of Edgewater Unit 5 through 2023. Retail electric rate changes were effective on January 1, 2022 and extend through the end of 2023. Retail gas rate changes were effective on January 1, 2022 and extended through the end of 2022.
WPL [Member]
Regulatory Matters [Line Items]
Regulatory Matters	REGULATORY MATTERS Regulatory Assets - Alliant Energy, IPL and WPL assess whether IPL’s and WPL’s regulatory assets are probable of future recovery by considering factors such as applicable regulations, recent orders by the applicable regulatory agencies, historical treatment of similar costs by the applicable regulatory agencies and regulatory environment changes. Based on these assessments, Alliant Energy, IPL and WPL believe the regulatory assets recognized as of December 31, 2022 are probable of future recovery. However, no assurance can be made that IPL and WPL will recover all of these regulatory assets in future rates. If future recovery of a regulatory asset ceases to be probable, the regulatory asset will be charged to expense. At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $929 $934 $848 $884 $81 $50 Pension and OPEB costs 392 462 197 228 195 234 Commodity cost recovery 160 42 1 2 159 40 AROs 151 128 110 89 41 39 Derivatives 84 8 48 4 36 4 Assets retired early 70 92 53 66 17 26 IPL’s DAEC PPA amendment 66 90 66 90 — — WPL’s Western Wisconsin gas distribution expansion investments 48 52 — — 48 52 Other 146 132 63 80 83 52 $2,046 $1,940 $1,386 $1,443 $660 $497 At December 31, 2022, IPL and WPL had $66 million and $28 million, respectively, of regulatory assets that were not earning a return on investment. IPL’s regulatory assets that were not earning a return consisted primarily of retired analog electric meters, emission allowances and costs for certain construction projects. WPL’s regulatory assets that were not earning a return consisted primarily of amounts related to the wholesale portion of under-collected costs, and costs for future expansion projects. The other regulatory assets reported in the above table either earn a return or the cash has not yet been expended, in which case the assets are offset by liabilities that also do not incur a carrying cost. Tax-related - IPL and WPL record regulatory assets for certain temporary differences (primarily related to utility property, plant and equipment at IPL) that result in a decrease in current rates charged to customers and an increase in future rates charged to customers based on the timing of income tax expense that is used to determine such rates. These temporary differences for IPL include the impacts of qualifying deductions for repairs expenditures, allocation of mixed service costs, and Iowa accelerated tax depreciation, which all contribute to lower current income tax expense during the first part of an asset’s useful life and higher current income tax expense during the latter part of an asset’s useful life. These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates. Refer to Note 12 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in 2022. Pension and other postretirement benefits costs - The IUB, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates. These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs. Regulatory assets are also increased or decreased as a result of the annual defined benefit plan measurement process. Pension and OPEB costs are included within the recoverable cost of service component of rates charged to IPL’s and WPL’s retail and wholesale customers, which are based upon pension and OPEB costs determined in accordance with GAAP and are calculated in accordance with IPL’s and WPL’s respective regulatory jurisdictions. Commodity cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s commodity cost recovery mechanisms. The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. In 2021, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $37 million deferral as of December 31, 2022, which will be collected in 2023 from its retail electric customers, plus interest. In 2022, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $117 million deferral as of December 31, 2022, which is currently expected to be addressed in WPL’s next retail electric rate review. AROs - Alliant Energy, IPL and WPL believe it is probable that certain differences between expenses accrued for AROs related to their utility operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets. Derivatives - In accordance with IPL’s and WPL’s fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recoverable from customers in the future after any losses are realized, and gains from derivative instruments are refundable to customers in the future after any gains are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Refer to Note 15 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during 2022, which result in comparable changes to regulatory assets/liabilities on the balance sheets. Assets retired early - IPL and WPL have retired various natural gas- and coal-fired EGUs, and IPL has retired certain analog electric meters. As a result, the remaining net book value of these assets was reclassified from property, plant and equipment to a regulatory asset on their respective balance sheets. Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2022 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $16 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 13 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 24 Return of remaining net book value through 2028 IUB and FERC WPL Edgewater Unit 4 2018 17 Return of and return on remaining net book value through 2028 PSCW and FERC IPL’s DAEC PPA Amendment - In 2020, IPL made a buyout payment of $110 million in exchange for shortening the term of its DAEC PPA by 5 years. The payment was included in “DAEC PPA amendment buyout payment” in Alliant Energy’s and IPL’s cash flows used for operating activities in 2020. The buyout payment, including a return on, will be recovered from IPL’s retail and wholesale customers from 2021 through the end of 2025, and is currently being amortized to “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. WPL’s Western Wisconsin gas distribution expansion investments - WPL made contributions in aid of construction to a third party for investments as part of its Western Wisconsin gas distribution expansion project. Pursuant to authorization by the PSCW, Alliant Energy and WPL have recorded a regulatory asset for these costs, and are authorized by the PSCW to recover these amounts from WPL’s retail gas customers in base rates from 2021 through the end of 2040. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $579 $585 $303 $312 $276 $273 Cost of removal obligations 398 384 259 252 139 132 Derivatives 210 166 115 77 95 89 Commodity cost recovery 40 17 38 15 2 2 WPL’s West Riverside liquidated damages 32 36 — — 32 36 Electric transmission cost recovery 20 51 10 27 10 24 Other 45 32 29 8 16 24 $1,324 $1,271 $754 $691 $570 $580 Tax-related regulatory liabilities reduce revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings. Cost of removal obligations, to the extent expensed through depreciation rates, reduce rate base. A significant portion of the remaining regulatory liabilities is not used to adjust revenue requirement calculations. Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform. The majority of these benefits related to accelerated depreciation are subject to tax normalization rules. These rules limit the rate at which these tax benefits are allowed to be passed on to customers. Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated AROs or that have removal costs in addition to AROs. Alliant Energy, IPL and WPL record a regulatory liability for the amounts collected in rates for these future removal costs and reduce the regulatory liability for amounts spent on removal activities. Cash payments related to cost of removal obligations are included in “Other” in cash flows used for investing activities. WPL’s West Riverside liquidated damages - Pursuant to terms included in the related West Riverside construction procurement contracts, WPL reached agreement with the contractor on liquidated damages in 2020. A significant portion of the liquidated damages was settled by WPL offsetting amounts owed to the contractor that were previously withheld for payment, which were non-cash investing activities. In 2020, the PSCW authorized WPL to record the liquidated damages as a regulatory liability, which the PSCW authorized to be returned to WPL’s retail customers in 2022 and 2023, resulting 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 in 2022. Electric transmission cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s electric transmission cost recovery mechanisms. In 2020, pursuant to an IUB order, IPL issued $42 million of credits to its retail electric customers through its transmission cost rider for amounts previously collected in rates, which resulted in a reduction to “Electric transmission service” expense in Alliant Energy’s and IPL’s income statements in 2020. Derecho Windstorm - In August 2020, a derecho windstorm caused considerable damage to IPL’s electric distribution system in its service territory, and over 250,000 of its customers lost power. IPL completed its initial restoration and rebuilding efforts in August 2020. As of December 31, 2022, approximately $140 million of costs from the windstorm were recorded substantially to “Property, plant and equipment, net” on Alliant Energy’s and IPL’s balance sheets. In December 2020, IPL received approval from the IUB for utilization of a regulatory account to track certain incremental costs and benefits incurred resulting from the windstorm. These incremental costs and benefits were not addressed in the IUB’s order for IPL’s 2020 forward-looking Test Period electric subsequent proceeding, and are expected to be addressed in future regulatory proceedings. Tax benefits and the incremental operation and maintenance expenses resulting from the windstorm were deferred and recorded as a net regulatory liability of $8 million as of December 31, 2022, which is included in “Other” regulatory liabilities in the above table. Rate Reviews - IPL’s Retail Electric Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers based on a 2020 forward-looking Test Period. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric base rate increase of $90 million, on an annual basis, was implemented effective April 1, 2019. In October 2019, IPL reached a settlement agreement with certain stakeholders for an annual retail electric base rate increase of $127 million. In January 2020, the IUB issued an order approving the settlement with final rates, which were effective February 26, 2020. The agreement includes both the recovery of and a return on IPL’s early retired EGUs, and the recovery of IPL’s retired analog electric meters. In addition, as discussed in Note 1(g) , the net impact of certain costs and benefits resulting from IPL’s 1,000 MW expansion of wind generation in 2019 and 2020 is being recovered from its retail electric customers through the renewable energy rider. The agreement also includes IPL providing retail electric billing credits, which began in the third quarter of 2020 through June 2021, and in aggregate include $27 million of excess deferred tax benefits and $8 million from a partial refund of interim rates implemented in 2019. In 2021, the IUB issued an order for IPL’s 2020 forward-looking Test Period electric subsequent proceeding, which compared actual revenues and costs to those initially forecasted by IPL, and authorized IPL to maintain its current retail electric rates. IPL’s Retail Gas Rate Review (2020 Forward-looking Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers based on a 2020 forward-looking Test Period. In October 2019, IPL reached a settlement agreement with certain stakeholders for an annual retail gas base rate increase of $12 million. In December 2019, the IUB issued an order approving the settlement with final rates, which were effective January 10, 2020. In 2021, the IUB issued an order for IPL’s 2020 forward-looking Test Period gas subsequent proceeding, which compared actual revenues and costs to those initially forecasted by IPL, and authorized IPL to maintain its current retail gas rates. WPL’s Retail Electric and Gas Rate Review (2019/2020 Forward-looking Test Period) - In December 2018, the PSCW issued an order approving WPL’s proposed settlement for its retail electric and gas rate review covering the 2019/2020 Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. Under the settlement, WPL retail electric and gas base rates did not change from then current levels through the end of 2020. In September 2020, pursuant to an August 2020 PSCW order, WPL refunded $12 million of 2019 fuel-related cost over-collections to its retail electric customers. In addition, WPL’s amortization of excess deferred taxes resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform was used to offset increases in WPL’s 2020 increased revenue requirements. WPL’s Retail Electric and Gas Rate Review (2021 Forward-looking Test Period) - In December 2020, the PSCW issued an order authorizing WPL to maintain its then current retail electric and gas base rates, authorized return on common equity, regulatory capital structure and earnings sharing mechanism through the end of 2021. WPL utilized anticipated fuel-related cost savings and excess deferred income tax benefits in 2021 to offset the revenue requirement impacts of increasing electric and gas rate base, including the Kossuth wind farm, which was placed in service in October 2020, and the expansion of its gas distribution system in Western Wisconsin, which was placed in service in November 2020. WPL’s Retail Electric and Gas Rate Reviews (2022/2023 Forward-looking Test Period) - In December 2021, the PSCW issued an order authorizing annual base rate increases of $114 million and $15 million for WPL’s retail electric and gas customers, respectively, covering the 2022/2023 forward-looking Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. The key drivers for the annual base rate increases include higher retail fuel-related costs in 2022, lower excess deferred income tax benefits in 2022 and 2023 and revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation. In addition, the PSCW authorized WPL to receive a recovery of and a return on the remaining net book value of Edgewater Unit 5 through 2023. Retail electric rate changes were effective on January 1, 2022 and extend through the end of 2023. Retail gas rate changes were effective on January 1, 2022 and extended through the end of 2022.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Utility: Electric plant: Generation in service $8,060 $7,539 $4,962 $4,922 $3,098 $2,617 Distribution in service 6,912 6,537 3,876 3,652 3,036 2,885 Other in service 543 540 354 363 189 177 Anticipated to be retired early (a) 2,103 2,094 491 487 1,612 1,607 Total electric plant 17,618 16,710 9,683 9,424 7,935 7,286 Gas plant in service 1,705 1,636 910 878 795 758 Other plant in service 624 621 402 398 222 223 Accumulated depreciation (5,690) (5,263) (3,149) (2,897) (2,541) (2,366) Net plant 14,257 13,704 7,846 7,803 6,411 5,901 Leased Sheboygan Falls Energy Facility, net (b) — — — — 15 21 Leased land for solar generation, net 133 11 — — 133 11 Construction work in progress 1,357 778 194 174 1,163 604 Other, net 6 7 6 6 — 1 Total utility 15,753 14,500 8,046 7,983 7,722 6,538 Non-utility and other: Non-utility Generation, net (c) 71 75 — — — — Corporate Services and other, net (d) 423 412 — — — — Total non-utility and other 494 487 — — — — Total property, plant and equipment $16,247 $14,987 $8,046 $7,983 $7,722 $6,538 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing in the first half of 2023 and Edgewater Unit 5 by June 1, 2025. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and IPL concluded that Lansing, and Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2, met the criteria to be considered probable of abandonment as of December 31, 2022. IPL and WPL are currently allowed a full recovery of and a full return on its respective EGUs from both its retail and wholesale customers, and as a result, Alliant Energy, IPL and WPL concluded that no disallowance was required as of December 31, 2022. As of December 31, 2022, net book values were $233 million for Lansing, $511 million for Edgewater Unit 5, and $440 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $106 million and $100 million for WPL as of December 31, 2022 and 2021, respectively. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (c) Less accumulated depreciation of $71 million and $67 million for Alliant Energy as of December 31, 2022 and 2021, respectively. (d) Less accumulated depreciation of $269 million and $245 million for Alliant Energy as of December 31, 2022 and 2021, respectively. AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Equity $44 $18 $39 $8 $7 $17 $36 $11 $22 Debt 16 7 16 3 2 7 13 5 9 $60 $25 $55 $11 $9 $24 $49 $16 $31 Non-utility and Other - The non-utility and other property, plant and equipment recorded on Alliant Energy’s balance sheets include the following: Non-utility Generation - The Sheboygan Falls Energy Facility was placed in service in 2005 and is depreciated using the straight-line method over a 35-year period. Corporate Services and Other - Property, plant and equipment related to Corporate Services include a customer billing and information system for IPL and WPL and other computer software, and the corporate headquarters building located in Madison, Wisconsin. The customer billing and information system is amortized using the straight-line method over a 12-year period. The majority of the remaining software is amortized over a 5-year period. Other property, plant and equipment include Travero assets (a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; and a rail-served warehouse in Iowa). All Corporate Services and Other property, plant and equipment are depreciated using the straight-line method over periods ranging from 5 to 30 years.
IPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Utility: Electric plant: Generation in service $8,060 $7,539 $4,962 $4,922 $3,098 $2,617 Distribution in service 6,912 6,537 3,876 3,652 3,036 2,885 Other in service 543 540 354 363 189 177 Anticipated to be retired early (a) 2,103 2,094 491 487 1,612 1,607 Total electric plant 17,618 16,710 9,683 9,424 7,935 7,286 Gas plant in service 1,705 1,636 910 878 795 758 Other plant in service 624 621 402 398 222 223 Accumulated depreciation (5,690) (5,263) (3,149) (2,897) (2,541) (2,366) Net plant 14,257 13,704 7,846 7,803 6,411 5,901 Leased Sheboygan Falls Energy Facility, net (b) — — — — 15 21 Leased land for solar generation, net 133 11 — — 133 11 Construction work in progress 1,357 778 194 174 1,163 604 Other, net 6 7 6 6 — 1 Total utility 15,753 14,500 8,046 7,983 7,722 6,538 Non-utility and other: Non-utility Generation, net (c) 71 75 — — — — Corporate Services and other, net (d) 423 412 — — — — Total non-utility and other 494 487 — — — — Total property, plant and equipment $16,247 $14,987 $8,046 $7,983 $7,722 $6,538 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing in the first half of 2023 and Edgewater Unit 5 by June 1, 2025. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and IPL concluded that Lansing, and Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2, met the criteria to be considered probable of abandonment as of December 31, 2022. IPL and WPL are currently allowed a full recovery of and a full return on its respective EGUs from both its retail and wholesale customers, and as a result, Alliant Energy, IPL and WPL concluded that no disallowance was required as of December 31, 2022. As of December 31, 2022, net book values were $233 million for Lansing, $511 million for Edgewater Unit 5, and $440 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $106 million and $100 million for WPL as of December 31, 2022 and 2021, respectively. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (c) Less accumulated depreciation of $71 million and $67 million for Alliant Energy as of December 31, 2022 and 2021, respectively. (d) Less accumulated depreciation of $269 million and $245 million for Alliant Energy as of December 31, 2022 and 2021, respectively. AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Equity $44 $18 $39 $8 $7 $17 $36 $11 $22 Debt 16 7 16 3 2 7 13 5 9 $60 $25 $55 $11 $9 $24 $49 $16 $31
WPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Utility: Electric plant: Generation in service $8,060 $7,539 $4,962 $4,922 $3,098 $2,617 Distribution in service 6,912 6,537 3,876 3,652 3,036 2,885 Other in service 543 540 354 363 189 177 Anticipated to be retired early (a) 2,103 2,094 491 487 1,612 1,607 Total electric plant 17,618 16,710 9,683 9,424 7,935 7,286 Gas plant in service 1,705 1,636 910 878 795 758 Other plant in service 624 621 402 398 222 223 Accumulated depreciation (5,690) (5,263) (3,149) (2,897) (2,541) (2,366) Net plant 14,257 13,704 7,846 7,803 6,411 5,901 Leased Sheboygan Falls Energy Facility, net (b) — — — — 15 21 Leased land for solar generation, net 133 11 — — 133 11 Construction work in progress 1,357 778 194 174 1,163 604 Other, net 6 7 6 6 — 1 Total utility 15,753 14,500 8,046 7,983 7,722 6,538 Non-utility and other: Non-utility Generation, net (c) 71 75 — — — — Corporate Services and other, net (d) 423 412 — — — — Total non-utility and other 494 487 — — — — Total property, plant and equipment $16,247 $14,987 $8,046 $7,983 $7,722 $6,538 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing in the first half of 2023 and Edgewater Unit 5 by June 1, 2025. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and IPL concluded that Lansing, and Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2, met the criteria to be considered probable of abandonment as of December 31, 2022. IPL and WPL are currently allowed a full recovery of and a full return on its respective EGUs from both its retail and wholesale customers, and as a result, Alliant Energy, IPL and WPL concluded that no disallowance was required as of December 31, 2022. As of December 31, 2022, net book values were $233 million for Lansing, $511 million for Edgewater Unit 5, and $440 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $106 million and $100 million for WPL as of December 31, 2022 and 2021, respectively. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (c) Less accumulated depreciation of $71 million and $67 million for Alliant Energy as of December 31, 2022 and 2021, respectively. (d) Less accumulated depreciation of $269 million and $245 million for Alliant Energy as of December 31, 2022 and 2021, respectively. AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Equity $44 $18 $39 $8 $7 $17 $36 $11 $22 Debt 16 7 16 3 2 7 13 5 9 $60 $25 $55 $11 $9 $24 $49 $16 $31

Jointly-Owned Electric Utility

Jointly-Owned Electric Utility Plant	12 Months Ended
	Dec. 31, 2022
Jointly-Owned Electric Utility Plant	JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2022 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $612 $241 $17 George Neal Unit 4 25.7% 193 103 4 George Neal Unit 3 28.0% 176 80 6 Louisa Unit 1 4.0% 43 21 — 1,024 445 27 WPL Columbia Units 1-2 53.5% 805 338 13 West Riverside Energy Center and Solar Facility 91.0% 716 53 2 Forward Wind Energy Center 42.6% 118 50 — 1,639 441 15 Alliant Energy $2,663 $886 $42
IPL [Member]
Jointly-Owned Electric Utility Plant	JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2022 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $612 $241 $17 George Neal Unit 4 25.7% 193 103 4 George Neal Unit 3 28.0% 176 80 6 Louisa Unit 1 4.0% 43 21 — 1,024 445 27 WPL Columbia Units 1-2 53.5% 805 338 13 West Riverside Energy Center and Solar Facility 91.0% 716 53 2 Forward Wind Energy Center 42.6% 118 50 — 1,639 441 15 Alliant Energy $2,663 $886 $42
WPL [Member]
Jointly-Owned Electric Utility Plant	JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2022 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $612 $241 $17 George Neal Unit 4 25.7% 193 103 4 George Neal Unit 3 28.0% 176 80 6 Louisa Unit 1 4.0% 43 21 — 1,024 445 27 WPL Columbia Units 1-2 53.5% 805 338 13 West Riverside Energy Center and Solar Facility 91.0% 716 53 2 Forward Wind Energy Center 42.6% 118 50 — 1,639 441 15 Alliant Energy $2,663 $886 $42

Receivables

Receivables	12 Months Ended
	Dec. 31, 2022
Accounts Receivable [Line Items]
Receivables	RECEIVABLES(a) Accounts Receivable - Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Customer $114 $93 $— $— $102 $82 Unbilled utility revenues 115 91 — — 115 91 Deferred proceeds 185 214 185 214 — — Other 109 53 74 28 34 25 Allowance for expected credit losses (7) (11) — (1) (7) (10) $516 $440 $259 $241 $244 $188 IPL maintains a Receivables Agreement whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The purchase commitment from the third party to which IPL sells its receivables expires in March 2023. IPL currently expects to amend and extend the purchase commitment. IPL pays a monthly fee to the third party that varies based on interest rates, limits on cash proceeds and cash amounts received from the third party. Deferred proceeds represent IPL’s interest in the receivables sold to the third party. At IPL’s request, deferred proceeds are paid to IPL from collections of receivables, after paying any required expenses incurred by the third party and the collection agent. Corporate Services acts as collection agent for the third party and receives a fee for collection services. The Receivables Agreement can be terminated by the third party if arrears or write-offs exceed certain levels. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. IPL believes that the allowance for expected credit losses related to its sales of receivables is a reasonable approximation of credit risk of the customers that generated the receivables. Refer to Note 16 for discussion of the fair value of deferred proceeds. Maximum Average 2022 2021 2020 2022 2021 2020 Outstanding aggregate cash proceeds $80 $110 $96 $14 $46 $9 As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 Customer accounts receivable $145 $125 Unbilled utility revenues 132 104 Receivables sold to third party 277 229 Less: cash proceeds 80 1 Deferred proceeds 197 228 Less: allowance for expected credit losses 12 14 Fair value of deferred proceeds $185 $214 Outstanding receivables past due $26 $22 Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 2020 Collections $2,302 $2,134 $2,025 Write-offs, net of recoveries 9 9 7
IPL [Member]
Accounts Receivable [Line Items]
Receivables	RECEIVABLES(a) Accounts Receivable - Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Customer $114 $93 $— $— $102 $82 Unbilled utility revenues 115 91 — — 115 91 Deferred proceeds 185 214 185 214 — — Other 109 53 74 28 34 25 Allowance for expected credit losses (7) (11) — (1) (7) (10) $516 $440 $259 $241 $244 $188 IPL maintains a Receivables Agreement whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The purchase commitment from the third party to which IPL sells its receivables expires in March 2023. IPL currently expects to amend and extend the purchase commitment. IPL pays a monthly fee to the third party that varies based on interest rates, limits on cash proceeds and cash amounts received from the third party. Deferred proceeds represent IPL’s interest in the receivables sold to the third party. At IPL’s request, deferred proceeds are paid to IPL from collections of receivables, after paying any required expenses incurred by the third party and the collection agent. Corporate Services acts as collection agent for the third party and receives a fee for collection services. The Receivables Agreement can be terminated by the third party if arrears or write-offs exceed certain levels. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. IPL believes that the allowance for expected credit losses related to its sales of receivables is a reasonable approximation of credit risk of the customers that generated the receivables. Refer to Note 16 for discussion of the fair value of deferred proceeds. Maximum Average 2022 2021 2020 2022 2021 2020 Outstanding aggregate cash proceeds $80 $110 $96 $14 $46 $9 As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 Customer accounts receivable $145 $125 Unbilled utility revenues 132 104 Receivables sold to third party 277 229 Less: cash proceeds 80 1 Deferred proceeds 197 228 Less: allowance for expected credit losses 12 14 Fair value of deferred proceeds $185 $214 Outstanding receivables past due $26 $22 Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 2020 Collections $2,302 $2,134 $2,025 Write-offs, net of recoveries 9 9 7
WPL [Member]
Accounts Receivable [Line Items]
Receivables	RECEIVABLES(a) Accounts Receivable - Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Customer $114 $93 $— $— $102 $82 Unbilled utility revenues 115 91 — — 115 91 Deferred proceeds 185 214 185 214 — — Other 109 53 74 28 34 25 Allowance for expected credit losses (7) (11) — (1) (7) (10) $516 $440 $259 $241 $244 $188

Investments

Investments	12 Months Ended
	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investments	INVESTMENTS Unconsolidated Equity Investments - Alliant Energy’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions): Ownership Interest at Carrying Value at December 31, Equity (Income) / Loss December 31, 2022 2022 2021 2022 2021 2020 ATC Holdings 16%, 20% $358 $338 ($41) ($43) ($47) Non-utility wind farm in Oklahoma 50% 101 99 (5) (4) (8) Corporate venture investments Various 62 52 (3) (13) (4) Other Various 21 19 (2) (2) (2) $542 $508 ($51) ($62) ($61) Summary aggregate financial information from the financial statements of these holdings is as follows (in millions): Alliant Energy 2022 2021 2020 Revenues $813 $802 $801 Operating income 350 357 376 Net income 675 358 343 As of December 31: Current assets 227 112 Non-current assets 8,292 7,036 Current liabilities 620 455 Non-current liabilities 3,285 3,110 Noncontrolling interest 289 247 ATC Holdings - As of December 31, 2022, Alliant Energy has a 16% ownership interest in ATC and a 20% ownership interest in ATC Holdco LLC, collectively referred to as ATC Holdings. ATC is an independent, for-profit, transmission-only company. ATC Holdco LLC holds Duke-American Transmission Company, LLC, a joint venture between Duke Energy Corporation and ATC, that owns electric transmission infrastructure in North America. Refer to Note 17(g) for discussion of a reduction in earnings recorded in 2022 related to a court decision, which is currently expected to reduce the base return on equity authorized for MISO transmission owners, including ATC. Non-utility Wind Farm in Oklahoma - The non-utility wind farm located in Oklahoma provides electricity to a third-party under a long-term PPA, and has both cash and tax equity ownership. Alliant Energy does not maintain or operate the wind farm, and provided a parent guarantee of its subsidiary’s indemnification obligations under the operating agreement and PPA. Refer to Note 17(d) for discussion of the guarantee. Corporate Venture Investments - Alliant Energy has various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy.

Common Equity

Common Equity	12 Months Ended
	Dec. 31, 2022
Schedule of Common Equity [Line Items]
Common Equity	COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: 2022 2021 2020 Shares outstanding, January 1 250,474,529 249,868,415 245,022,800 Equity forward agreements — — 4,275,127 Shareowner Direct Plan 437,669 492,565 472,283 Equity-based compensation plans 222,768 113,549 98,205 Shares outstanding, December 31 251,134,966 250,474,529 249,868,415 At December 31, 2022, Alliant Energy had a total of 13 million shares available for issuance in the aggregate, pursuant to its 2020 OIP, Shareowner Direct Plan and 401(k) Savings Plan. 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. Alliant Energy has not issued any shares under this program. Equity Forward Agreements - In 2019, Alliant Energy entered into forward sale agreements with a counterparty in connection with a public offering of 4,275,127 shares of Alliant Energy common stock. In 2020, Alliant Energy settled $222 million under the forward sale agreements by delivering 4,275,127 shares of newly issued Alliant Energy common stock at a weighted average forward sale price of $51.98 per share. Alliant Energy used the net proceeds from the settlements for general corporate purposes. Shareowner Direct Plan - Alliant Energy satisfies its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market.

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2022
Preferred Stock	PREFERRED STOCKIn 2021, IPL redeemed all 8,000,000 outstanding shares of its 5.1% cumulative preferred stock at the $25 per share par value for $200 million plus accrued and unpaid dividends up to the redemption date. In 2021, Alliant Energy and IPL recorded a $5 million non-cash charge related to this transaction in “Preferred dividend requirements” in their income statements.
IPL [Member]
Preferred Stock	PREFERRED STOCKIn 2021, IPL redeemed all 8,000,000 outstanding shares of its 5.1% cumulative preferred stock at the $25 per share par value for $200 million plus accrued and unpaid dividends up to the redemption date. In 2021, Alliant Energy and IPL recorded a $5 million non-cash charge related to this transaction in “Preferred dividend requirements” in their income statements.

Debt

Debt	12 Months Ended
	Dec. 31, 2022
Debt Instrument [Line Items]
Debt	DEBT(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2022, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2026, totaled $1 billion ($500 million for Alliant Energy at the parent company level, $100 million for IPL and $400 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, 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): Alliant Energy IPL WPL December 31 2022 2021 2022 2021 2022 2021 Amount outstanding $642 $515 $— $— $290 $236 Weighted average interest rates 4.6% 0.2% N/A N/A 4.5% 0.2% Available credit facility capacity $358 $485 $100 $250 $110 $64 Alliant Energy IPL WPL For the year ended 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $665 $648 $— $19 $325 $320 Average amount outstanding (based on daily outstanding balances) $411 $459 $— $— $153 $172 Weighted average interest rates 2.1% 0.2% —% 0.2% 1.6% 0.1% 2022 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 3.25%, due 2024 $500 $500 $— $500 $500 $— 3.4%, due 2025 250 250 — 250 250 — 5.5%, due 2025 50 50 — 50 50 — 4.1%, due 2028 500 500 — 500 500 — 3.6%, due 2029 300 300 — 300 300 — 2.3%, due 2030 400 400 — 400 400 — 6.45%, due 2033 100 100 — 100 100 — 6.3%, due 2034 125 125 — 125 125 — 6.25%, due 2039 300 300 — 300 300 — 4.7%, due 2043 250 250 — 250 250 — 3.7%, due 2046 300 300 — 300 300 — 3.5%, due 2049 300 300 — 300 300 — 3.1%, due 2051 300 300 — 300 300 — 3,675 3,675 — 3,675 3,675 — Debentures (a): 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 300 — 300 300 — 300 3.95%, due 2032 (b) 600 — 600 — — — 6.25%, due 2034 100 — 100 100 — 100 6.375%, due 2037 300 — 300 300 — 300 7.6%, due 2038 250 — 250 250 — 250 4.1%, due 2044 250 — 250 250 — 250 3.65%, due 2050 350 — 350 350 — 350 2.25% (Retired in 2022) — — — 250 — 250 2,800 — 2,800 2,450 — 2,450 Other: AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 400 — — AEF term loan credit agreement through March 2024, 5% at December 31, 2022 (with Alliant Energy as guarantor) (c) 400 — — — — — AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)(d) 350 — — — — — Sheboygan Power, LLC 5.06% senior secured notes, due 2023 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 17 — — 24 — — AEF term loan credit agreement, 1% at December 31, 2021 (with Alliant Energy as guarantor) (Retired in 2022) — — — 300 — — Corporate Services 3.45% senior notes (Retired in 2022) — — — 75 — — Other, 1% at December 31, 2022, due 2023 to 2025 1 — — 1 — — 1,668 — — 1,300 — — Subtotal 8,143 3,675 2,800 7,425 3,675 2,450 Current maturities (408) — — (633) — (250) Unamortized debt issuance costs (45) (21) (19) (42) (23) (15) Unamortized debt (discount) and premium, net (22) (8) (11) (15) (9) (6) Long-term debt, net (e) $7,668 $3,646 $2,770 $6,735 $3,643 $2,179 (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In August 2022, WPL issued $600 million of 3.95% debentures due 2032. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of WPL’s solar EGUs. (c) In March 2022, AEF entered into a $300 million variable rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022. In December 2022, AEF increased the amount outstanding under the new term loan credit agreement by $100 million and used the additional borrowings to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026. Under the terms of the swap, AEF exchanged variable rate borrowings for a fixed rate of 3.93%. (d) In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. (e) There were no significant sinking fund requirements related to the outstanding long-term debt. In December 2022, AEF entered into a $50 million variable rate term loan credit agreement (with Alliant Energy as guarantor), which expires in January 2024. AEF received the proceeds from the issuance in January 2023, and used the borrowings under this agreement to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2022, long-term debt maturities for 2023 through 2027 were as follows (in millions): 2023 2024 2025 2026 2027 IPL $— $500 $300 $— $— WPL — — — — 300 AEF 408 409 — 200 — Alliant Energy $408 $909 $300 $200 $300 Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.
IPL [Member]
Debt Instrument [Line Items]
Debt	DEBT(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2022, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2026, totaled $1 billion ($500 million for Alliant Energy at the parent company level, $100 million for IPL and $400 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, 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): Alliant Energy IPL WPL December 31 2022 2021 2022 2021 2022 2021 Amount outstanding $642 $515 $— $— $290 $236 Weighted average interest rates 4.6% 0.2% N/A N/A 4.5% 0.2% Available credit facility capacity $358 $485 $100 $250 $110 $64 Alliant Energy IPL WPL For the year ended 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $665 $648 $— $19 $325 $320 Average amount outstanding (based on daily outstanding balances) $411 $459 $— $— $153 $172 Weighted average interest rates 2.1% 0.2% —% 0.2% 1.6% 0.1% 2022 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 3.25%, due 2024 $500 $500 $— $500 $500 $— 3.4%, due 2025 250 250 — 250 250 — 5.5%, due 2025 50 50 — 50 50 — 4.1%, due 2028 500 500 — 500 500 — 3.6%, due 2029 300 300 — 300 300 — 2.3%, due 2030 400 400 — 400 400 — 6.45%, due 2033 100 100 — 100 100 — 6.3%, due 2034 125 125 — 125 125 — 6.25%, due 2039 300 300 — 300 300 — 4.7%, due 2043 250 250 — 250 250 — 3.7%, due 2046 300 300 — 300 300 — 3.5%, due 2049 300 300 — 300 300 — 3.1%, due 2051 300 300 — 300 300 — 3,675 3,675 — 3,675 3,675 — Debentures (a): 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 300 — 300 300 — 300 3.95%, due 2032 (b) 600 — 600 — — — 6.25%, due 2034 100 — 100 100 — 100 6.375%, due 2037 300 — 300 300 — 300 7.6%, due 2038 250 — 250 250 — 250 4.1%, due 2044 250 — 250 250 — 250 3.65%, due 2050 350 — 350 350 — 350 2.25% (Retired in 2022) — — — 250 — 250 2,800 — 2,800 2,450 — 2,450 Other: AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 400 — — AEF term loan credit agreement through March 2024, 5% at December 31, 2022 (with Alliant Energy as guarantor) (c) 400 — — — — — AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)(d) 350 — — — — — Sheboygan Power, LLC 5.06% senior secured notes, due 2023 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 17 — — 24 — — AEF term loan credit agreement, 1% at December 31, 2021 (with Alliant Energy as guarantor) (Retired in 2022) — — — 300 — — Corporate Services 3.45% senior notes (Retired in 2022) — — — 75 — — Other, 1% at December 31, 2022, due 2023 to 2025 1 — — 1 — — 1,668 — — 1,300 — — Subtotal 8,143 3,675 2,800 7,425 3,675 2,450 Current maturities (408) — — (633) — (250) Unamortized debt issuance costs (45) (21) (19) (42) (23) (15) Unamortized debt (discount) and premium, net (22) (8) (11) (15) (9) (6) Long-term debt, net (e) $7,668 $3,646 $2,770 $6,735 $3,643 $2,179 (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In August 2022, WPL issued $600 million of 3.95% debentures due 2032. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of WPL’s solar EGUs. (c) In March 2022, AEF entered into a $300 million variable rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022. In December 2022, AEF increased the amount outstanding under the new term loan credit agreement by $100 million and used the additional borrowings to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026. Under the terms of the swap, AEF exchanged variable rate borrowings for a fixed rate of 3.93%. (d) In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. (e) There were no significant sinking fund requirements related to the outstanding long-term debt. In December 2022, AEF entered into a $50 million variable rate term loan credit agreement (with Alliant Energy as guarantor), which expires in January 2024. AEF received the proceeds from the issuance in January 2023, and used the borrowings under this agreement to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2022, long-term debt maturities for 2023 through 2027 were as follows (in millions): 2023 2024 2025 2026 2027 IPL $— $500 $300 $— $— WPL — — — — 300 AEF 408 409 — 200 — Alliant Energy $408 $909 $300 $200 $300 Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.
WPL [Member]
Debt Instrument [Line Items]
Debt	DEBT(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2022, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2026, totaled $1 billion ($500 million for Alliant Energy at the parent company level, $100 million for IPL and $400 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, 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): Alliant Energy IPL WPL December 31 2022 2021 2022 2021 2022 2021 Amount outstanding $642 $515 $— $— $290 $236 Weighted average interest rates 4.6% 0.2% N/A N/A 4.5% 0.2% Available credit facility capacity $358 $485 $100 $250 $110 $64 Alliant Energy IPL WPL For the year ended 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $665 $648 $— $19 $325 $320 Average amount outstanding (based on daily outstanding balances) $411 $459 $— $— $153 $172 Weighted average interest rates 2.1% 0.2% —% 0.2% 1.6% 0.1% 2022 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 3.25%, due 2024 $500 $500 $— $500 $500 $— 3.4%, due 2025 250 250 — 250 250 — 5.5%, due 2025 50 50 — 50 50 — 4.1%, due 2028 500 500 — 500 500 — 3.6%, due 2029 300 300 — 300 300 — 2.3%, due 2030 400 400 — 400 400 — 6.45%, due 2033 100 100 — 100 100 — 6.3%, due 2034 125 125 — 125 125 — 6.25%, due 2039 300 300 — 300 300 — 4.7%, due 2043 250 250 — 250 250 — 3.7%, due 2046 300 300 — 300 300 — 3.5%, due 2049 300 300 — 300 300 — 3.1%, due 2051 300 300 — 300 300 — 3,675 3,675 — 3,675 3,675 — Debentures (a): 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 300 — 300 300 — 300 3.95%, due 2032 (b) 600 — 600 — — — 6.25%, due 2034 100 — 100 100 — 100 6.375%, due 2037 300 — 300 300 — 300 7.6%, due 2038 250 — 250 250 — 250 4.1%, due 2044 250 — 250 250 — 250 3.65%, due 2050 350 — 350 350 — 350 2.25% (Retired in 2022) — — — 250 — 250 2,800 — 2,800 2,450 — 2,450 Other: AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 400 — — AEF term loan credit agreement through March 2024, 5% at December 31, 2022 (with Alliant Energy as guarantor) (c) 400 — — — — — AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)(d) 350 — — — — — Sheboygan Power, LLC 5.06% senior secured notes, due 2023 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 17 — — 24 — — AEF term loan credit agreement, 1% at December 31, 2021 (with Alliant Energy as guarantor) (Retired in 2022) — — — 300 — — Corporate Services 3.45% senior notes (Retired in 2022) — — — 75 — — Other, 1% at December 31, 2022, due 2023 to 2025 1 — — 1 — — 1,668 — — 1,300 — — Subtotal 8,143 3,675 2,800 7,425 3,675 2,450 Current maturities (408) — — (633) — (250) Unamortized debt issuance costs (45) (21) (19) (42) (23) (15) Unamortized debt (discount) and premium, net (22) (8) (11) (15) (9) (6) Long-term debt, net (e) $7,668 $3,646 $2,770 $6,735 $3,643 $2,179 (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In August 2022, WPL issued $600 million of 3.95% debentures due 2032. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of WPL’s solar EGUs. (c) In March 2022, AEF entered into a $300 million variable rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022. In December 2022, AEF increased the amount outstanding under the new term loan credit agreement by $100 million and used the additional borrowings to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026. Under the terms of the swap, AEF exchanged variable rate borrowings for a fixed rate of 3.93%. (d) In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. (e) There were no significant sinking fund requirements related to the outstanding long-term debt. In December 2022, AEF entered into a $50 million variable rate term loan credit agreement (with Alliant Energy as guarantor), which expires in January 2024. AEF received the proceeds from the issuance in January 2023, and used the borrowings under this agreement to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2022, long-term debt maturities for 2023 through 2027 were as follows (in millions): 2023 2024 2025 2026 2027 IPL $— $500 $300 $— $— WPL — — — — 300 AEF 408 409 — 200 — Alliant Energy $408 $909 $300 $200 $300 Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.

Leases

Leases	12 Months Ended
	Dec. 31, 2022
Leases [Line Items]
Operating Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below. Related to its investments in solar generation, WPL entered into land lease agreements with unaffiliated parties that commenced in 2021 and 2022. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments. Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12 In 2022, Alliant Energy’s and WPL’s finance lease liabilities arising from obtaining leased assets were $125 million, which represent non-cash financing activities. Expected Maturities - As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
Finance Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below. Related to its investments in solar generation, WPL entered into land lease agreements with unaffiliated parties that commenced in 2021 and 2022. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments. Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12 In 2022, Alliant Energy’s and WPL’s finance lease liabilities arising from obtaining leased assets were $125 million, which represent non-cash financing activities. Expected Maturities - As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
IPL [Member]
Leases [Line Items]
Operating Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below. Related to its investments in solar generation, WPL entered into land lease agreements with unaffiliated parties that commenced in 2021 and 2022. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments. Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12 In 2022, Alliant Energy’s and WPL’s finance lease liabilities arising from obtaining leased assets were $125 million, which represent non-cash financing activities. Expected Maturities - As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
WPL [Member]
Leases [Line Items]
Operating Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below. Related to its investments in solar generation, WPL entered into land lease agreements with unaffiliated parties that commenced in 2021 and 2022. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments. Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12 In 2022, Alliant Energy’s and WPL’s finance lease liabilities arising from obtaining leased assets were $125 million, which represent non-cash financing activities. Expected Maturities - As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
Finance Leases	LEASES Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business through 2025, the initial lease term. WPL is responsible for the operation of the EGU and has exclusive rights to its output. This finance lease contains two lease renewal periods, which are not included in the finance lease obligation, as well as an option to purchase the facility at the end of the initial lease term. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below. Related to its investments in solar generation, WPL entered into land lease agreements with unaffiliated parties that commenced in 2021 and 2022. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments. Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12 In 2022, Alliant Energy’s and WPL’s finance lease liabilities arising from obtaining leased assets were $125 million, which represent non-cash financing activities. Expected Maturities - As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167

Revenues

Revenues	12 Months Ended
	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues	REVENUES Revenues from Alliant Energy’s, IPL’s and WPL’s utility businesses are primarily from electric and gas sales provided to customers based on approved tariffs or specific contracts with customers. IPL’s and WPL’s primary performance obligations under such arrangements are to deliver electricity and gas, and their customers simultaneously receive and consume the electricity and gas. For such arrangements, revenues are recognized equivalent to the value of the electricity or gas supplied during each period, including amounts billed during each period and changes in amounts estimated to be billed at the end of each period. IPL and WPL apply the right to invoice method to measure progress towards completing performance obligations to transfer electricity and gas to their customers. IPL provides retail electric and gas service to customers in Iowa, and WPL provides retail and wholesale electric and retail gas service to customers in Wisconsin. IPL also provides electricity to wholesale customers in Minnesota, Illinois and Iowa, as well as steam from its Prairie Creek Generating Station to high-pressure steam customers in Iowa. IPL’s and WPL’s retail electric and gas revenues include sales to residential, commercial and industrial customers. IPL’s and WPL’s retail electric and gas customer prices are based on IPL’s and WPL’s cost of service and are determined through general rate review proceedings and various tariff filings with the IUB and PSCW, respectively. Such tariff-based services provide electricity or gas to customers without a defined contractual term. IPL and WPL have wholesale electric market-based rate authority from FERC allowing them to participate in wholesale energy markets (e.g. MISO) and transact directly with third parties. This authority from FERC allows sales of electricity referred to as bulk power sales based on current market values. FERC also allows IPL and WPL to enter into power supply agreements with municipalities and rural electric cooperatives with defined contractual terms, which include standard pricing mechanisms that are detailed in current tariffs accepted by FERC through wholesale rate review proceedings. Revenues from Alliant Energy’s non-utility business customers are primarily from its Travero business, which includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Electric Utility: Retail - residential $1,233 $1,115 $1,093 $673 $620 $602 $560 $495 $491 Retail - commercial 821 763 718 536 508 474 285 255 244 Retail - industrial 965 893 841 538 505 488 427 388 353 Wholesale 233 187 168 64 57 57 169 130 111 Bulk power and other 169 123 100 48 62 74 121 61 26 Total Electric Utility 3,421 3,081 2,920 1,859 1,752 1,695 1,562 1,329 1,225 Gas Utility: Retail - residential 371 257 214 202 146 116 169 111 98 Retail - commercial 197 139 107 101 79 59 96 60 48 Retail - industrial 20 17 12 14 12 8 6 5 4 Transportation/other 54 43 40 34 28 25 20 15 15 Total Gas Utility 642 456 373 351 265 208 291 191 165 Other Utility: Steam 39 36 36 39 36 36 — — — Other utility 10 13 13 7 10 8 3 3 5 Total Other Utility 49 49 49 46 46 44 3 3 5 Non-Utility and Other: Travero and other 93 83 74 — — — — — — Total Non-Utility and Other 93 83 74 — — — — — — Total revenues $4,205 $3,669 $3,416 $2,256 $2,063 $1,947 $1,856 $1,523 $1,395
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	REVENUES Revenues from Alliant Energy’s, IPL’s and WPL’s utility businesses are primarily from electric and gas sales provided to customers based on approved tariffs or specific contracts with customers. IPL’s and WPL’s primary performance obligations under such arrangements are to deliver electricity and gas, and their customers simultaneously receive and consume the electricity and gas. For such arrangements, revenues are recognized equivalent to the value of the electricity or gas supplied during each period, including amounts billed during each period and changes in amounts estimated to be billed at the end of each period. IPL and WPL apply the right to invoice method to measure progress towards completing performance obligations to transfer electricity and gas to their customers. IPL provides retail electric and gas service to customers in Iowa, and WPL provides retail and wholesale electric and retail gas service to customers in Wisconsin. IPL also provides electricity to wholesale customers in Minnesota, Illinois and Iowa, as well as steam from its Prairie Creek Generating Station to high-pressure steam customers in Iowa. IPL’s and WPL’s retail electric and gas revenues include sales to residential, commercial and industrial customers. IPL’s and WPL’s retail electric and gas customer prices are based on IPL’s and WPL’s cost of service and are determined through general rate review proceedings and various tariff filings with the IUB and PSCW, respectively. Such tariff-based services provide electricity or gas to customers without a defined contractual term. IPL and WPL have wholesale electric market-based rate authority from FERC allowing them to participate in wholesale energy markets (e.g. MISO) and transact directly with third parties. This authority from FERC allows sales of electricity referred to as bulk power sales based on current market values. FERC also allows IPL and WPL to enter into power supply agreements with municipalities and rural electric cooperatives with defined contractual terms, which include standard pricing mechanisms that are detailed in current tariffs accepted by FERC through wholesale rate review proceedings. Revenues from Alliant Energy’s non-utility business customers are primarily from its Travero business, which includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Electric Utility: Retail - residential $1,233 $1,115 $1,093 $673 $620 $602 $560 $495 $491 Retail - commercial 821 763 718 536 508 474 285 255 244 Retail - industrial 965 893 841 538 505 488 427 388 353 Wholesale 233 187 168 64 57 57 169 130 111 Bulk power and other 169 123 100 48 62 74 121 61 26 Total Electric Utility 3,421 3,081 2,920 1,859 1,752 1,695 1,562 1,329 1,225 Gas Utility: Retail - residential 371 257 214 202 146 116 169 111 98 Retail - commercial 197 139 107 101 79 59 96 60 48 Retail - industrial 20 17 12 14 12 8 6 5 4 Transportation/other 54 43 40 34 28 25 20 15 15 Total Gas Utility 642 456 373 351 265 208 291 191 165 Other Utility: Steam 39 36 36 39 36 36 — — — Other utility 10 13 13 7 10 8 3 3 5 Total Other Utility 49 49 49 46 46 44 3 3 5 Non-Utility and Other: Travero and other 93 83 74 — — — — — — Total Non-Utility and Other 93 83 74 — — — — — — Total revenues $4,205 $3,669 $3,416 $2,256 $2,063 $1,947 $1,856 $1,523 $1,395
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	REVENUES Revenues from Alliant Energy’s, IPL’s and WPL’s utility businesses are primarily from electric and gas sales provided to customers based on approved tariffs or specific contracts with customers. IPL’s and WPL’s primary performance obligations under such arrangements are to deliver electricity and gas, and their customers simultaneously receive and consume the electricity and gas. For such arrangements, revenues are recognized equivalent to the value of the electricity or gas supplied during each period, including amounts billed during each period and changes in amounts estimated to be billed at the end of each period. IPL and WPL apply the right to invoice method to measure progress towards completing performance obligations to transfer electricity and gas to their customers. IPL provides retail electric and gas service to customers in Iowa, and WPL provides retail and wholesale electric and retail gas service to customers in Wisconsin. IPL also provides electricity to wholesale customers in Minnesota, Illinois and Iowa, as well as steam from its Prairie Creek Generating Station to high-pressure steam customers in Iowa. IPL’s and WPL’s retail electric and gas revenues include sales to residential, commercial and industrial customers. IPL’s and WPL’s retail electric and gas customer prices are based on IPL’s and WPL’s cost of service and are determined through general rate review proceedings and various tariff filings with the IUB and PSCW, respectively. Such tariff-based services provide electricity or gas to customers without a defined contractual term. IPL and WPL have wholesale electric market-based rate authority from FERC allowing them to participate in wholesale energy markets (e.g. MISO) and transact directly with third parties. This authority from FERC allows sales of electricity referred to as bulk power sales based on current market values. FERC also allows IPL and WPL to enter into power supply agreements with municipalities and rural electric cooperatives with defined contractual terms, which include standard pricing mechanisms that are detailed in current tariffs accepted by FERC through wholesale rate review proceedings. Revenues from Alliant Energy’s non-utility business customers are primarily from its Travero business, which includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa. Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Electric Utility: Retail - residential $1,233 $1,115 $1,093 $673 $620 $602 $560 $495 $491 Retail - commercial 821 763 718 536 508 474 285 255 244 Retail - industrial 965 893 841 538 505 488 427 388 353 Wholesale 233 187 168 64 57 57 169 130 111 Bulk power and other 169 123 100 48 62 74 121 61 26 Total Electric Utility 3,421 3,081 2,920 1,859 1,752 1,695 1,562 1,329 1,225 Gas Utility: Retail - residential 371 257 214 202 146 116 169 111 98 Retail - commercial 197 139 107 101 79 59 96 60 48 Retail - industrial 20 17 12 14 12 8 6 5 4 Transportation/other 54 43 40 34 28 25 20 15 15 Total Gas Utility 642 456 373 351 265 208 291 191 165 Other Utility: Steam 39 36 36 39 36 36 — — — Other utility 10 13 13 7 10 8 3 3 5 Total Other Utility 49 49 49 46 46 44 3 3 5 Non-Utility and Other: Travero and other 93 83 74 — — — — — — Total Non-Utility and Other 93 83 74 — — — — — — Total revenues $4,205 $3,669 $3,416 $2,256 $2,063 $1,947 $1,856 $1,523 $1,395

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Tax [Line Items]
Income Taxes	INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Current tax expense (benefit): Federal $7 $1 $1 ($29) ($21) $6 $46 $22 ($11) State 2 3 8 (8) (1) (1) 16 6 7 Deferred tax expense (benefit): Federal 109 9 22 91 73 30 10 (75) (9) State 28 15 8 1 — (2) 12 11 10 Production tax credits (123) (101) (95) (105) (87) (80) (18) (14) (15) Investment tax credits (1) (1) (1) — — — — (1) (1) $22 ($74) ($57) ($50) ($36) ($47) $66 ($51) ($19) Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Statutory federal income tax rate 21% 21% 21% 21% 21% 21% 21% 21% 21% State income taxes, net of federal benefits 3 2 2 (2) (1) (1) 6 6 6 Production tax credits (18) (17) (17) (34) (27) (28) (5) (6) (7) Amortization of excess deferred taxes (Refer to Note 2 ) (2) (18) (13) (2) (4) (5) (3) (43) (26) Effect of rate-making on property-related differences (1) (1) (3) (1) (2) (4) (2) (1) (2) Adjustment for prior period taxes 1 1 1 1 2 1 — — — Other items, net (1) — (1) 1 — — — (1) — Overall income tax rate 3% (12%) (10%) (16%) (11%) (16%) 17% (24%) (8%) Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Deferred tax liabilities: Property $2,442 $2,389 $1,440 $1,416 $938 $913 ATC Holdings 125 123 — — — — Other 155 111 86 76 80 50 Total deferred tax liabilities 2,722 2,623 1,526 1,492 1,018 963 Deferred tax assets: Federal credit carryforwards 672 560 450 345 209 192 Net operating losses carryforwards - federal — 39 — 36 — — Net operating losses carryforwards - state 32 38 — 3 — — Other 75 65 29 25 20 18 Subtotal deferred tax assets 779 702 479 409 229 210 Valuation allowances — (6) — — — — Total deferred tax assets 779 696 479 409 229 210 Total deferred tax liabilities, net $1,943 $1,927 $1,047 $1,083 $789 $753 Carryforwards - At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2042 $527 $10 $1 Federal tax credits 2024-2042 672 450 209 Valuation Allowances - In 2022, Alliant Energy fully utilized its federal net operating losses carryforwards. This allowed for the utilization of federal tax credit carryforwards prior to their expiration, resulting in the reversal of Alliant Energy’s valuation allowances in 2022. Uncertain Tax Positions - At December 31, 2022, 2021 and 2020, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2022, no material changes to unrecognized tax benefits are expected during the next 12 months. Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2019 - 2021 Consolidated Iowa income tax returns (b) 2019 - 2021 Wisconsin combined tax returns (c) 2018 - 2021 (a) The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date. Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior. In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4%, effective January 1, 2023. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2023, which resulted in a $77 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a decrease in their deferred tax liabilities in 2022. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2023, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and a decrease in deferred income tax assets on Alliant Energy’s balance sheet in 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.
IPL [Member]
Income Tax [Line Items]
Income Taxes	INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Current tax expense (benefit): Federal $7 $1 $1 ($29) ($21) $6 $46 $22 ($11) State 2 3 8 (8) (1) (1) 16 6 7 Deferred tax expense (benefit): Federal 109 9 22 91 73 30 10 (75) (9) State 28 15 8 1 — (2) 12 11 10 Production tax credits (123) (101) (95) (105) (87) (80) (18) (14) (15) Investment tax credits (1) (1) (1) — — — — (1) (1) $22 ($74) ($57) ($50) ($36) ($47) $66 ($51) ($19) Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Statutory federal income tax rate 21% 21% 21% 21% 21% 21% 21% 21% 21% State income taxes, net of federal benefits 3 2 2 (2) (1) (1) 6 6 6 Production tax credits (18) (17) (17) (34) (27) (28) (5) (6) (7) Amortization of excess deferred taxes (Refer to Note 2 ) (2) (18) (13) (2) (4) (5) (3) (43) (26) Effect of rate-making on property-related differences (1) (1) (3) (1) (2) (4) (2) (1) (2) Adjustment for prior period taxes 1 1 1 1 2 1 — — — Other items, net (1) — (1) 1 — — — (1) — Overall income tax rate 3% (12%) (10%) (16%) (11%) (16%) 17% (24%) (8%) Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Deferred tax liabilities: Property $2,442 $2,389 $1,440 $1,416 $938 $913 ATC Holdings 125 123 — — — — Other 155 111 86 76 80 50 Total deferred tax liabilities 2,722 2,623 1,526 1,492 1,018 963 Deferred tax assets: Federal credit carryforwards 672 560 450 345 209 192 Net operating losses carryforwards - federal — 39 — 36 — — Net operating losses carryforwards - state 32 38 — 3 — — Other 75 65 29 25 20 18 Subtotal deferred tax assets 779 702 479 409 229 210 Valuation allowances — (6) — — — — Total deferred tax assets 779 696 479 409 229 210 Total deferred tax liabilities, net $1,943 $1,927 $1,047 $1,083 $789 $753 Carryforwards - At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2042 $527 $10 $1 Federal tax credits 2024-2042 672 450 209 Valuation Allowances - In 2022, Alliant Energy fully utilized its federal net operating losses carryforwards. This allowed for the utilization of federal tax credit carryforwards prior to their expiration, resulting in the reversal of Alliant Energy’s valuation allowances in 2022. Uncertain Tax Positions - At December 31, 2022, 2021 and 2020, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2022, no material changes to unrecognized tax benefits are expected during the next 12 months. Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2019 - 2021 Consolidated Iowa income tax returns (b) 2019 - 2021 Wisconsin combined tax returns (c) 2018 - 2021 (a) The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date. Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior. In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4%, effective January 1, 2023. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2023, which resulted in a $77 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a decrease in their deferred tax liabilities in 2022. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2023, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and a decrease in deferred income tax assets on Alliant Energy’s balance sheet in 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.
WPL [Member]
Income Tax [Line Items]
Income Taxes	INCOME TAXES Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Current tax expense (benefit): Federal $7 $1 $1 ($29) ($21) $6 $46 $22 ($11) State 2 3 8 (8) (1) (1) 16 6 7 Deferred tax expense (benefit): Federal 109 9 22 91 73 30 10 (75) (9) State 28 15 8 1 — (2) 12 11 10 Production tax credits (123) (101) (95) (105) (87) (80) (18) (14) (15) Investment tax credits (1) (1) (1) — — — — (1) (1) $22 ($74) ($57) ($50) ($36) ($47) $66 ($51) ($19) Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Statutory federal income tax rate 21% 21% 21% 21% 21% 21% 21% 21% 21% State income taxes, net of federal benefits 3 2 2 (2) (1) (1) 6 6 6 Production tax credits (18) (17) (17) (34) (27) (28) (5) (6) (7) Amortization of excess deferred taxes (Refer to Note 2 ) (2) (18) (13) (2) (4) (5) (3) (43) (26) Effect of rate-making on property-related differences (1) (1) (3) (1) (2) (4) (2) (1) (2) Adjustment for prior period taxes 1 1 1 1 2 1 — — — Other items, net (1) — (1) 1 — — — (1) — Overall income tax rate 3% (12%) (10%) (16%) (11%) (16%) 17% (24%) (8%) Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Deferred tax liabilities: Property $2,442 $2,389 $1,440 $1,416 $938 $913 ATC Holdings 125 123 — — — — Other 155 111 86 76 80 50 Total deferred tax liabilities 2,722 2,623 1,526 1,492 1,018 963 Deferred tax assets: Federal credit carryforwards 672 560 450 345 209 192 Net operating losses carryforwards - federal — 39 — 36 — — Net operating losses carryforwards - state 32 38 — 3 — — Other 75 65 29 25 20 18 Subtotal deferred tax assets 779 702 479 409 229 210 Valuation allowances — (6) — — — — Total deferred tax assets 779 696 479 409 229 210 Total deferred tax liabilities, net $1,943 $1,927 $1,047 $1,083 $789 $753 Carryforwards - At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2042 $527 $10 $1 Federal tax credits 2024-2042 672 450 209 Valuation Allowances - In 2022, Alliant Energy fully utilized its federal net operating losses carryforwards. This allowed for the utilization of federal tax credit carryforwards prior to their expiration, resulting in the reversal of Alliant Energy’s valuation allowances in 2022. Uncertain Tax Positions - At December 31, 2022, 2021 and 2020, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2022, no material changes to unrecognized tax benefits are expected during the next 12 months. Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2019 - 2021 Consolidated Iowa income tax returns (b) 2019 - 2021 Wisconsin combined tax returns (c) 2018 - 2021 (a) The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date. Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior. In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4%, effective January 1, 2023. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcement of the new Iowa corporate income tax rate, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured based upon the new rate effective January 1, 2023, which resulted in a $77 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a decrease in their deferred tax liabilities in 2022. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rate effective January 1, 2023, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and a decrease in deferred income tax assets on Alliant Energy’s balance sheet in 2022. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2022
Benefit Plans	BENEFIT PLANS(a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans (currently closed to new hires), and/or through defined contribution plans (including 401(k) savings plans). Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. For IPL and WPL, amounts below represent the amounts 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. Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.91% 2.57% 5.53% 2.81% 2.31% Discount rate for net periodic cost 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.40% 4.80% 4.50% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 9.22% 4.18% 4.76% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.30% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.55% 2.94% 2.61% 5.53% 2.80% 2.28% Discount rate for net periodic cost 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.50% 5.10% 4.50% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.94% 2.64% 5.53% 2.79% 2.27% Discount rate for net periodic cost 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 5.49% 4.02% 3.28% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Expected rate of return on plan assets - The expected rate of return on plan assets is based on projected asset class returns using target allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are analyzed to support the expected rate of return on plan assets assumption. Refer to “ Investment Strategy for Plan Assets ” below for additional information related to investment strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption utilizes base mortality tables that were released in 2019 by the Society of Actuaries and mortality projection tables that were released in 2021 by the Society of Actuaries. Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $9 $11 $11 $3 $4 $3 Interest cost 36 34 43 6 5 7 Expected return on plan assets (a) (69) (69) (70) (5) (5) (5) Amortization of prior service credit (b) (1) — — — — — Amortization of actuarial loss (c) 32 39 34 2 5 3 Settlement losses (d) 26 — 12 — — — $33 $15 $30 $6 $9 $8 IPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $6 $7 $7 $1 $1 $1 Interest cost 16 16 20 2 2 3 Expected return on plan assets (a) (31) (32) (33) (4) (3) (4) Amortization of actuarial loss (c) 13 17 15 1 2 1 Settlement losses (d) 13 — 7 — — — $17 $8 $16 $— $2 $1 WPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $3 $4 $4 $1 $1 $2 Interest cost 16 15 19 2 2 3 Expected return on plan assets (a) (31) (31) (31) (1) — (1) Amortization of prior service credit (b) — — — — — (1) Amortization of actuarial loss (c) 15 19 16 2 2 2 Settlement losses (d) 13 — — — — — $16 $7 $8 $4 $5 $5 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. (d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan. Benefit Plan Assets and Obligations - A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $1,251 $1,351 $210 $227 Service cost 9 11 3 4 Interest cost 36 34 6 5 Plan participants’ contributions — — 4 5 Actuarial gain (269) (46) (37) (12) Gross benefits paid (152) (99) (18) (19) Net benefit obligation at December 31 875 1,251 168 210 Change in plan assets: Fair value of plan assets at January 1 1,011 984 106 108 Actual return on plan assets (204) 87 (17) 4 Employer contributions 51 39 8 8 Plan participants’ contributions — — 4 5 Gross benefits paid (152) (99) (18) (19) Fair value of plan assets at December 31 706 1,011 83 106 Under funded status at December 31 ($169) ($240) ($85) ($104) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $9 $13 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (167) (238) (86) (109) Net amounts recognized at December 31 ($169) ($240) ($85) ($104) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $376 $429 $20 $38 Prior service credit (3) (4) — (1) $373 $425 $20 $37 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $567 $615 $84 $91 Service cost 6 7 1 1 Interest cost 16 16 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (123) (23) (14) (4) Gross benefits paid (77) (48) (7) (8) Net benefit obligation at December 31 389 567 68 84 Change in plan assets: Fair value of plan assets at January 1 462 453 74 74 Actual return on plan assets (92) 40 (12) 4 Employer contributions 51 17 1 2 Plan participants’ contributions — — 2 2 Gross benefits paid (77) (48) (7) (8) Fair value of plan assets at December 31 344 462 58 74 Under funded status at December 31 ($45) ($105) ($10) ($10) Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $6 $10 Current liabilities — — (2) (2) Pension and other benefit obligations (45) (105) (14) (18) Net amounts recognized at December 31 ($45) ($105) ($10) ($10) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $154 $180 $14 $13 Prior service credit (1) (1) — — $153 $179 $14 $13 Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $546 $588 $81 $89 Service cost 3 4 1 1 Interest cost 16 15 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (117) (18) (13) (5) Gross benefits paid (67) (43) (8) (8) Net benefit obligation at December 31 381 546 65 81 Change in plan assets: Fair value of plan assets at January 1 450 436 17 18 Actual return on plan assets (92) 39 (2) — Employer contributions — 18 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (67) (43) (8) (8) Fair value of plan assets at December 31 291 450 14 17 Under funded status at December 31 ($90) ($96) ($51) ($64) Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (5) (6) Pension and other benefit obligations (90) (96) (49) (61) Net amounts recognized at December 31 ($90) ($96) ($51) ($64) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $165 $188 $6 $18 Prior service credit — (1) — (1) $165 $187 $6 $17 Actuarial gains related to benefit obligations in 2022 and 2021 for defined benefit pension and OPEB plans were primarily due to increases in the discount rates. Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Accumulated benefit obligations $857 $1,214 $168 $210 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 857 1,214 168 210 Fair value of plan assets 706 1,011 83 106 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 875 1,251 N/A N/A Fair value of plan assets 706 1,011 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Accumulated benefit obligations $379 $546 $68 $84 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 379 546 68 84 Fair value of plan assets 344 462 58 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 389 567 N/A N/A Fair value of plan assets 344 462 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Accumulated benefit obligations $373 $532 $65 $81 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 373 532 65 81 Fair value of plan assets 291 450 14 17 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 381 546 N/A N/A Fair value of plan assets 291 450 N/A N/A In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2022 2021 2022 2021 Regulatory assets $30 $35 $25 $30 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2023 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $12 $1 $10 OPEB plans 8 2 6 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $72 $71 $72 $74 $74 $349 OPEB 18 18 18 17 16 69 $90 $89 $90 $91 $90 $418 IPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $34 $33 $34 $33 $32 $155 OPEB 7 7 7 7 7 27 $41 $40 $41 $40 $39 $182 WPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $32 $31 $31 $31 $31 $148 OPEB 7 7 7 7 6 26 $39 $38 $38 $38 $37 $174 Investment Strategy for Plan Assets - Investment strategies for defined benefit pension and OPEB plan assets combine preservation of principal and prudent risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. Investment risk of plan assets is mitigated through diversification, including U.S. and international equity, fixed income and global asset strategies. Global asset strategies may include investments in global equity, global debt and currencies. Defined Benefit Pension Plan Assets - The asset mix of defined benefit pension plans is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investments include, but are not limited to, direct ownership of real estate, oil and gas limited partnerships, securities of the managers’ firms or affiliate firms, and Alliant Energy securities. The allocations shown below exclude market exposure obtained through the overlay management service and cash held at IPL's qualified defined benefit pension plan as a result of a contribution made late in 2022. At December 31, 2022, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 4% Equity securities - U.S. 14% - 61% 33% Equity securities - international 11% - 31% 21% Global asset securities 2% - 11% 5% Fixed income securities 27% - 47% 37% Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. The investment strategy of the Corporate Services 401(h) assets mirrors those of the defined benefit pension plans, which are discussed above. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. At December 31, 2022, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 1% Equity securities - U.S. 0% - 55% 35% Fixed income securities 40% - 100% 64% Fair Value Measurements - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Refer to Note 16 for discussion of levels within the fair value hierarchy. Level 1 items include investments in securities held in registered investment companies and directly held equity securities, which are valued at the closing price reported in the active market in which the securities are traded. Level 2 items include cash and equivalents and fixed income securities. Cash and equivalents include money market fund investments and cash collateral supporting derivative financial instruments. Fixed income securities include corporate and government bonds, which are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Certain investments that are measured at fair value using the net asset value practical expedient have not been classified in the fair value hierarchy. These fair value amounts are included below to reconcile the fair value hierarchy to the respective total plan assets. At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $79 $— $79 $— $35 $— $35 $— Equity securities - U.S. 185 185 — — 256 256 — — Global asset securities 35 35 — — 52 52 — — Fixed income securities 130 30 100 — 191 47 144 — Total assets in fair value hierarchy 429 $250 $179 $— 534 $355 $179 $— Assets measured at net asset value 276 477 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) — (1) Total pension plan assets $706 $1,011 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $62 $— $62 $— $16 $— $16 $— Equity securities - U.S. 83 83 — — 117 117 — — Global asset securities 16 16 — — 24 24 — — Fixed income securities 58 13 45 — 87 21 66 — Total assets in fair value hierarchy 219 $112 $107 $— 244 $162 $82 $— Assets measured at net asset value 124 218 Accrued investment income 1 — Total pension plan assets $344 $462 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $13 $— $13 $— $16 $— $16 $— Equity securities - U.S. 82 82 — — 114 114 — — Global asset securities 16 16 — — 23 23 — — Fixed income securities 57 13 44 — 85 21 64 — Total assets in fair value hierarchy 168 $111 $57 $— 238 $158 $80 $— Assets measured at net asset value 122 212 Accrued investment income 1 — Total pension plan assets $291 $450 At December 31, the fair values of OPEB plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $3 $— $3 $— $5 $— $5 $— Equity securities - U.S. 9 9 — — 11 11 — — Global asset securities 1 1 — — 1 1 — — Fixed income securities 47 46 1 — 60 58 2 — Total assets in fair value hierarchy 60 $56 $4 $— 77 $70 $7 $— Assets measured at net asset value 23 29 Total OPEB plan assets $83 $106 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $1 $— $1 $— $1 $— $1 $— Equity securities - U.S. 5 5 — — 8 8 — — Fixed income securities 34 34 — — 42 42 — — Total assets in fair value hierarchy 40 $39 $1 $— 51 $50 $1 $— Assets measured at net asset value 18 23 Total OPEB plan assets $58 $74 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $— $— $— $— $1 $— $1 $— Equity securities - U.S. 1 1 — — 1 1 — — Fixed income securities 13 13 — — 15 15 — — Total OPEB plan assets $14 $14 $— $— $17 $16 $1 $— For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2022 and 2021. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock directly held by participants represented 10% and 9% of total assets in the 401(k) savings plans at December 31, 2022 and 2021, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 401(k) costs $28 $26 $25 $13 $13 $13 $13 $12 $12 Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Compensation expense $13 $14 $16 $7 $8 $9 $5 $6 $6 Income tax benefits 3 4 4 2 2 2 1 2 2 As of December 31, 2022, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $6 million, $3 million and $2 million, respectively, which is expected to be recognized over a weighted average period of between one year and two years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is recorded in “Other operation and maintenance” in the income statements. As of December 31, 2022, 320,084 shares were included in the calculation of diluted EPS related to the nonvested equity awards. Performance Shares - Equity Awards - Payouts of performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group. Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these performance shares is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a three-year performance period. The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. If minimum performance targets are not met during the performance period, these performance shares are forfeited. Compensation expense is recorded ratably over the performance period based on the fair value of the awards at the grant date. A summary of the performance shares activity, with amounts representing the target number of awards, was as follows: 2022 2021 2020 Shares Weighted Shares Weighted Shares Weighted Nonvested awards, January 1 196,429 $51.59 129,156 $54.63 74,193 $47.44 Granted 74,106 54.45 73,112 46.19 56,204 64.04 Vested (71,101) 47.48 — — — — Forfeited (9,161) 53.99 (5,839) 51.07 (1,241) 50.94 Nonvested awards, December 31 190,273 54.13 196,429 51.59 129,156 54.63 Restricted Stock Units - Equity Awards - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock unit grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these restricted stock units is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on the fair value of the awards on the grant date. A summary of the restricted stock units activity was as follows: 2022 2021 2020 Units Weighted Units Weighted Units Weighted Nonvested units, January 1 217,819 $50.54 146,549 $51.54 89,281 $46.04 Granted 77,122 56.88 80,152 48.65 61,056 59.42 Vested (82,770) 46.08 — — — — Forfeited (13,896) 55.53 (8,882) 49.84 (3,788) 49.01 Nonvested units, December 31 198,275 54.53 217,819 50.54 146,549 51.54 Performance Restricted Stock Units - Equity Awards - Payouts of performance restricted stock units are based upon achievement of certain performance targets during a three-year performance period, which currently includes specified growth of consolidated net income from continuing operations, as well as a diversity metric for the 2022 grants. The actual number of units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of units under each award type. If minimum performance targets are not met during the performance period, these units are forfeited. Performance restricted stock units are to be paid out in shares and are accounted for as equity awards. The fair value of each performance restricted stock unit is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on a probability assessment of payouts for the awards at each reporting period. A summary of the performance restricted stock units activity, with amounts representing the target number of units, was as follows: 2022 2021 2020 Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Nonvested units, January 1 196,429 $50.74 197,463 $47.31 206,065 $41.50 Granted 84,670 57.01 73,112 48.66 56,204 59.37 Vested (71,101) 46.24 (68,307) 38.60 (63,565) 39.12 Forfeited (10,124) 55.92 (5,839) 50.46 (1,241) 49.25 Nonvested units, December 31 199,874 54.74 196,429 50.74 197,463 47.31 Company Stock Account - The DCP does not permit diversification of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock. The deferred compensation obligations for participants’ company stock accounts are recorded in “Additional paid-in capital” and the shares of Alliant Energy common stock held in a rabbi trust to satisfy this obligation are recorded in “Shares in deferred compensation trust” on Alliant Energy’s balance sheets. At December 31, the carrying value of the deferred compensation obligation for the company stock account and the shares in the deferred compensation trust based on the historical value of the shares of Alliant Energy common stock contributed to the rabbi trust, and the fair market value of the shares held in the rabbi trust, were as follows (in millions): 2022 2021 Carrying value $13 $12 Fair market value 22 24 Interest, Equity and Mutual Fund Accounts - Distributions from participants’ interest, equity and mutual fund accounts are in the form of cash payments. The deferred compensation obligations for participants’ interest, equity and mutual fund accounts are recorded in “Pension and other benefit obligations” on the balance sheets. At December 31, 2022 and 2021, the carrying value of Alliant Energy’s deferred compensation obligations for participants’ interest, equity and mutual fund accounts, which approximates fair market value, was $19 million and $22 million, respectively.
IPL [Member]
Benefit Plans	BENEFIT PLANS(a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans (currently closed to new hires), and/or through defined contribution plans (including 401(k) savings plans). Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. For IPL and WPL, amounts below represent the amounts 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. Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.91% 2.57% 5.53% 2.81% 2.31% Discount rate for net periodic cost 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.40% 4.80% 4.50% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 9.22% 4.18% 4.76% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.30% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.55% 2.94% 2.61% 5.53% 2.80% 2.28% Discount rate for net periodic cost 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.50% 5.10% 4.50% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.94% 2.64% 5.53% 2.79% 2.27% Discount rate for net periodic cost 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 5.49% 4.02% 3.28% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Expected rate of return on plan assets - The expected rate of return on plan assets is based on projected asset class returns using target allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are analyzed to support the expected rate of return on plan assets assumption. Refer to “ Investment Strategy for Plan Assets ” below for additional information related to investment strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption utilizes base mortality tables that were released in 2019 by the Society of Actuaries and mortality projection tables that were released in 2021 by the Society of Actuaries. Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $9 $11 $11 $3 $4 $3 Interest cost 36 34 43 6 5 7 Expected return on plan assets (a) (69) (69) (70) (5) (5) (5) Amortization of prior service credit (b) (1) — — — — — Amortization of actuarial loss (c) 32 39 34 2 5 3 Settlement losses (d) 26 — 12 — — — $33 $15 $30 $6 $9 $8 IPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $6 $7 $7 $1 $1 $1 Interest cost 16 16 20 2 2 3 Expected return on plan assets (a) (31) (32) (33) (4) (3) (4) Amortization of actuarial loss (c) 13 17 15 1 2 1 Settlement losses (d) 13 — 7 — — — $17 $8 $16 $— $2 $1 WPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $3 $4 $4 $1 $1 $2 Interest cost 16 15 19 2 2 3 Expected return on plan assets (a) (31) (31) (31) (1) — (1) Amortization of prior service credit (b) — — — — — (1) Amortization of actuarial loss (c) 15 19 16 2 2 2 Settlement losses (d) 13 — — — — — $16 $7 $8 $4 $5 $5 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. (d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan. Benefit Plan Assets and Obligations - A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $1,251 $1,351 $210 $227 Service cost 9 11 3 4 Interest cost 36 34 6 5 Plan participants’ contributions — — 4 5 Actuarial gain (269) (46) (37) (12) Gross benefits paid (152) (99) (18) (19) Net benefit obligation at December 31 875 1,251 168 210 Change in plan assets: Fair value of plan assets at January 1 1,011 984 106 108 Actual return on plan assets (204) 87 (17) 4 Employer contributions 51 39 8 8 Plan participants’ contributions — — 4 5 Gross benefits paid (152) (99) (18) (19) Fair value of plan assets at December 31 706 1,011 83 106 Under funded status at December 31 ($169) ($240) ($85) ($104) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $9 $13 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (167) (238) (86) (109) Net amounts recognized at December 31 ($169) ($240) ($85) ($104) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $376 $429 $20 $38 Prior service credit (3) (4) — (1) $373 $425 $20 $37 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $567 $615 $84 $91 Service cost 6 7 1 1 Interest cost 16 16 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (123) (23) (14) (4) Gross benefits paid (77) (48) (7) (8) Net benefit obligation at December 31 389 567 68 84 Change in plan assets: Fair value of plan assets at January 1 462 453 74 74 Actual return on plan assets (92) 40 (12) 4 Employer contributions 51 17 1 2 Plan participants’ contributions — — 2 2 Gross benefits paid (77) (48) (7) (8) Fair value of plan assets at December 31 344 462 58 74 Under funded status at December 31 ($45) ($105) ($10) ($10) Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $6 $10 Current liabilities — — (2) (2) Pension and other benefit obligations (45) (105) (14) (18) Net amounts recognized at December 31 ($45) ($105) ($10) ($10) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $154 $180 $14 $13 Prior service credit (1) (1) — — $153 $179 $14 $13 Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $546 $588 $81 $89 Service cost 3 4 1 1 Interest cost 16 15 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (117) (18) (13) (5) Gross benefits paid (67) (43) (8) (8) Net benefit obligation at December 31 381 546 65 81 Change in plan assets: Fair value of plan assets at January 1 450 436 17 18 Actual return on plan assets (92) 39 (2) — Employer contributions — 18 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (67) (43) (8) (8) Fair value of plan assets at December 31 291 450 14 17 Under funded status at December 31 ($90) ($96) ($51) ($64) Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (5) (6) Pension and other benefit obligations (90) (96) (49) (61) Net amounts recognized at December 31 ($90) ($96) ($51) ($64) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $165 $188 $6 $18 Prior service credit — (1) — (1) $165 $187 $6 $17 Actuarial gains related to benefit obligations in 2022 and 2021 for defined benefit pension and OPEB plans were primarily due to increases in the discount rates. Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Accumulated benefit obligations $857 $1,214 $168 $210 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 857 1,214 168 210 Fair value of plan assets 706 1,011 83 106 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 875 1,251 N/A N/A Fair value of plan assets 706 1,011 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Accumulated benefit obligations $379 $546 $68 $84 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 379 546 68 84 Fair value of plan assets 344 462 58 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 389 567 N/A N/A Fair value of plan assets 344 462 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Accumulated benefit obligations $373 $532 $65 $81 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 373 532 65 81 Fair value of plan assets 291 450 14 17 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 381 546 N/A N/A Fair value of plan assets 291 450 N/A N/A In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2022 2021 2022 2021 Regulatory assets $30 $35 $25 $30 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2023 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $12 $1 $10 OPEB plans 8 2 6 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $72 $71 $72 $74 $74 $349 OPEB 18 18 18 17 16 69 $90 $89 $90 $91 $90 $418 IPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $34 $33 $34 $33 $32 $155 OPEB 7 7 7 7 7 27 $41 $40 $41 $40 $39 $182 WPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $32 $31 $31 $31 $31 $148 OPEB 7 7 7 7 6 26 $39 $38 $38 $38 $37 $174 Investment Strategy for Plan Assets - Investment strategies for defined benefit pension and OPEB plan assets combine preservation of principal and prudent risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. Investment risk of plan assets is mitigated through diversification, including U.S. and international equity, fixed income and global asset strategies. Global asset strategies may include investments in global equity, global debt and currencies. Defined Benefit Pension Plan Assets - The asset mix of defined benefit pension plans is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investments include, but are not limited to, direct ownership of real estate, oil and gas limited partnerships, securities of the managers’ firms or affiliate firms, and Alliant Energy securities. The allocations shown below exclude market exposure obtained through the overlay management service and cash held at IPL's qualified defined benefit pension plan as a result of a contribution made late in 2022. At December 31, 2022, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 4% Equity securities - U.S. 14% - 61% 33% Equity securities - international 11% - 31% 21% Global asset securities 2% - 11% 5% Fixed income securities 27% - 47% 37% Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. The investment strategy of the Corporate Services 401(h) assets mirrors those of the defined benefit pension plans, which are discussed above. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. At December 31, 2022, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 1% Equity securities - U.S. 0% - 55% 35% Fixed income securities 40% - 100% 64% Fair Value Measurements - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Refer to Note 16 for discussion of levels within the fair value hierarchy. Level 1 items include investments in securities held in registered investment companies and directly held equity securities, which are valued at the closing price reported in the active market in which the securities are traded. Level 2 items include cash and equivalents and fixed income securities. Cash and equivalents include money market fund investments and cash collateral supporting derivative financial instruments. Fixed income securities include corporate and government bonds, which are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Certain investments that are measured at fair value using the net asset value practical expedient have not been classified in the fair value hierarchy. These fair value amounts are included below to reconcile the fair value hierarchy to the respective total plan assets. At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $79 $— $79 $— $35 $— $35 $— Equity securities - U.S. 185 185 — — 256 256 — — Global asset securities 35 35 — — 52 52 — — Fixed income securities 130 30 100 — 191 47 144 — Total assets in fair value hierarchy 429 $250 $179 $— 534 $355 $179 $— Assets measured at net asset value 276 477 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) — (1) Total pension plan assets $706 $1,011 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $62 $— $62 $— $16 $— $16 $— Equity securities - U.S. 83 83 — — 117 117 — — Global asset securities 16 16 — — 24 24 — — Fixed income securities 58 13 45 — 87 21 66 — Total assets in fair value hierarchy 219 $112 $107 $— 244 $162 $82 $— Assets measured at net asset value 124 218 Accrued investment income 1 — Total pension plan assets $344 $462 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $13 $— $13 $— $16 $— $16 $— Equity securities - U.S. 82 82 — — 114 114 — — Global asset securities 16 16 — — 23 23 — — Fixed income securities 57 13 44 — 85 21 64 — Total assets in fair value hierarchy 168 $111 $57 $— 238 $158 $80 $— Assets measured at net asset value 122 212 Accrued investment income 1 — Total pension plan assets $291 $450 At December 31, the fair values of OPEB plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $3 $— $3 $— $5 $— $5 $— Equity securities - U.S. 9 9 — — 11 11 — — Global asset securities 1 1 — — 1 1 — — Fixed income securities 47 46 1 — 60 58 2 — Total assets in fair value hierarchy 60 $56 $4 $— 77 $70 $7 $— Assets measured at net asset value 23 29 Total OPEB plan assets $83 $106 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $1 $— $1 $— $1 $— $1 $— Equity securities - U.S. 5 5 — — 8 8 — — Fixed income securities 34 34 — — 42 42 — — Total assets in fair value hierarchy 40 $39 $1 $— 51 $50 $1 $— Assets measured at net asset value 18 23 Total OPEB plan assets $58 $74 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $— $— $— $— $1 $— $1 $— Equity securities - U.S. 1 1 — — 1 1 — — Fixed income securities 13 13 — — 15 15 — — Total OPEB plan assets $14 $14 $— $— $17 $16 $1 $— For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2022 and 2021. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock directly held by participants represented 10% and 9% of total assets in the 401(k) savings plans at December 31, 2022 and 2021, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 401(k) costs $28 $26 $25 $13 $13 $13 $13 $12 $12 Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Compensation expense $13 $14 $16 $7 $8 $9 $5 $6 $6 Income tax benefits 3 4 4 2 2 2 1 2 2 As of December 31, 2022, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $6 million, $3 million and $2 million, respectively, which is expected to be recognized over a weighted average period of between one year and two years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is recorded in “Other operation and maintenance” in the income statements. As of December 31, 2022, 320,084 shares were included in the calculation of diluted EPS related to the nonvested equity awards. Performance Shares - Equity Awards - Payouts of performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group. Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these performance shares is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a three-year performance period. The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. If minimum performance targets are not met during the performance period, these performance shares are forfeited. Compensation expense is recorded ratably over the performance period based on the fair value of the awards at the grant date. A summary of the performance shares activity, with amounts representing the target number of awards, was as follows: 2022 2021 2020 Shares Weighted Shares Weighted Shares Weighted Nonvested awards, January 1 196,429 $51.59 129,156 $54.63 74,193 $47.44 Granted 74,106 54.45 73,112 46.19 56,204 64.04 Vested (71,101) 47.48 — — — — Forfeited (9,161) 53.99 (5,839) 51.07 (1,241) 50.94 Nonvested awards, December 31 190,273 54.13 196,429 51.59 129,156 54.63 Restricted Stock Units - Equity Awards - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock unit grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these restricted stock units is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on the fair value of the awards on the grant date. A summary of the restricted stock units activity was as follows: 2022 2021 2020 Units Weighted Units Weighted Units Weighted Nonvested units, January 1 217,819 $50.54 146,549 $51.54 89,281 $46.04 Granted 77,122 56.88 80,152 48.65 61,056 59.42 Vested (82,770) 46.08 — — — — Forfeited (13,896) 55.53 (8,882) 49.84 (3,788) 49.01 Nonvested units, December 31 198,275 54.53 217,819 50.54 146,549 51.54 Performance Restricted Stock Units - Equity Awards - Payouts of performance restricted stock units are based upon achievement of certain performance targets during a three-year performance period, which currently includes specified growth of consolidated net income from continuing operations, as well as a diversity metric for the 2022 grants. The actual number of units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of units under each award type. If minimum performance targets are not met during the performance period, these units are forfeited. Performance restricted stock units are to be paid out in shares and are accounted for as equity awards. The fair value of each performance restricted stock unit is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on a probability assessment of payouts for the awards at each reporting period. A summary of the performance restricted stock units activity, with amounts representing the target number of units, was as follows: 2022 2021 2020 Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Nonvested units, January 1 196,429 $50.74 197,463 $47.31 206,065 $41.50 Granted 84,670 57.01 73,112 48.66 56,204 59.37 Vested (71,101) 46.24 (68,307) 38.60 (63,565) 39.12 Forfeited (10,124) 55.92 (5,839) 50.46 (1,241) 49.25 Nonvested units, December 31 199,874 54.74 196,429 50.74 197,463 47.31
WPL [Member]
Benefit Plans	BENEFIT PLANS(a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans (currently closed to new hires), and/or through defined contribution plans (including 401(k) savings plans). Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. For IPL and WPL, amounts below represent the amounts 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. Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.91% 2.57% 5.53% 2.81% 2.31% Discount rate for net periodic cost 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.40% 4.80% 4.50% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 9.22% 4.18% 4.76% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.30% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.55% 2.94% 2.61% 5.53% 2.80% 2.28% Discount rate for net periodic cost 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.50% 5.10% 4.50% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.94% 2.64% 5.53% 2.79% 2.27% Discount rate for net periodic cost 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 5.49% 4.02% 3.28% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Expected rate of return on plan assets - The expected rate of return on plan assets is based on projected asset class returns using target allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are analyzed to support the expected rate of return on plan assets assumption. Refer to “ Investment Strategy for Plan Assets ” below for additional information related to investment strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption utilizes base mortality tables that were released in 2019 by the Society of Actuaries and mortality projection tables that were released in 2021 by the Society of Actuaries. Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $9 $11 $11 $3 $4 $3 Interest cost 36 34 43 6 5 7 Expected return on plan assets (a) (69) (69) (70) (5) (5) (5) Amortization of prior service credit (b) (1) — — — — — Amortization of actuarial loss (c) 32 39 34 2 5 3 Settlement losses (d) 26 — 12 — — — $33 $15 $30 $6 $9 $8 IPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $6 $7 $7 $1 $1 $1 Interest cost 16 16 20 2 2 3 Expected return on plan assets (a) (31) (32) (33) (4) (3) (4) Amortization of actuarial loss (c) 13 17 15 1 2 1 Settlement losses (d) 13 — 7 — — — $17 $8 $16 $— $2 $1 WPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $3 $4 $4 $1 $1 $2 Interest cost 16 15 19 2 2 3 Expected return on plan assets (a) (31) (31) (31) (1) — (1) Amortization of prior service credit (b) — — — — — (1) Amortization of actuarial loss (c) 15 19 16 2 2 2 Settlement losses (d) 13 — — — — — $16 $7 $8 $4 $5 $5 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. (d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan. Benefit Plan Assets and Obligations - A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $1,251 $1,351 $210 $227 Service cost 9 11 3 4 Interest cost 36 34 6 5 Plan participants’ contributions — — 4 5 Actuarial gain (269) (46) (37) (12) Gross benefits paid (152) (99) (18) (19) Net benefit obligation at December 31 875 1,251 168 210 Change in plan assets: Fair value of plan assets at January 1 1,011 984 106 108 Actual return on plan assets (204) 87 (17) 4 Employer contributions 51 39 8 8 Plan participants’ contributions — — 4 5 Gross benefits paid (152) (99) (18) (19) Fair value of plan assets at December 31 706 1,011 83 106 Under funded status at December 31 ($169) ($240) ($85) ($104) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $9 $13 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (167) (238) (86) (109) Net amounts recognized at December 31 ($169) ($240) ($85) ($104) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $376 $429 $20 $38 Prior service credit (3) (4) — (1) $373 $425 $20 $37 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $567 $615 $84 $91 Service cost 6 7 1 1 Interest cost 16 16 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (123) (23) (14) (4) Gross benefits paid (77) (48) (7) (8) Net benefit obligation at December 31 389 567 68 84 Change in plan assets: Fair value of plan assets at January 1 462 453 74 74 Actual return on plan assets (92) 40 (12) 4 Employer contributions 51 17 1 2 Plan participants’ contributions — — 2 2 Gross benefits paid (77) (48) (7) (8) Fair value of plan assets at December 31 344 462 58 74 Under funded status at December 31 ($45) ($105) ($10) ($10) Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $6 $10 Current liabilities — — (2) (2) Pension and other benefit obligations (45) (105) (14) (18) Net amounts recognized at December 31 ($45) ($105) ($10) ($10) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $154 $180 $14 $13 Prior service credit (1) (1) — — $153 $179 $14 $13 Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $546 $588 $81 $89 Service cost 3 4 1 1 Interest cost 16 15 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (117) (18) (13) (5) Gross benefits paid (67) (43) (8) (8) Net benefit obligation at December 31 381 546 65 81 Change in plan assets: Fair value of plan assets at January 1 450 436 17 18 Actual return on plan assets (92) 39 (2) — Employer contributions — 18 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (67) (43) (8) (8) Fair value of plan assets at December 31 291 450 14 17 Under funded status at December 31 ($90) ($96) ($51) ($64) Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (5) (6) Pension and other benefit obligations (90) (96) (49) (61) Net amounts recognized at December 31 ($90) ($96) ($51) ($64) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $165 $188 $6 $18 Prior service credit — (1) — (1) $165 $187 $6 $17 Actuarial gains related to benefit obligations in 2022 and 2021 for defined benefit pension and OPEB plans were primarily due to increases in the discount rates. Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Accumulated benefit obligations $857 $1,214 $168 $210 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 857 1,214 168 210 Fair value of plan assets 706 1,011 83 106 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 875 1,251 N/A N/A Fair value of plan assets 706 1,011 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Accumulated benefit obligations $379 $546 $68 $84 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 379 546 68 84 Fair value of plan assets 344 462 58 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 389 567 N/A N/A Fair value of plan assets 344 462 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Accumulated benefit obligations $373 $532 $65 $81 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 373 532 65 81 Fair value of plan assets 291 450 14 17 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 381 546 N/A N/A Fair value of plan assets 291 450 N/A N/A In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2022 2021 2022 2021 Regulatory assets $30 $35 $25 $30 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2023 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $12 $1 $10 OPEB plans 8 2 6 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $72 $71 $72 $74 $74 $349 OPEB 18 18 18 17 16 69 $90 $89 $90 $91 $90 $418 IPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $34 $33 $34 $33 $32 $155 OPEB 7 7 7 7 7 27 $41 $40 $41 $40 $39 $182 WPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $32 $31 $31 $31 $31 $148 OPEB 7 7 7 7 6 26 $39 $38 $38 $38 $37 $174 Investment Strategy for Plan Assets - Investment strategies for defined benefit pension and OPEB plan assets combine preservation of principal and prudent risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. Investment risk of plan assets is mitigated through diversification, including U.S. and international equity, fixed income and global asset strategies. Global asset strategies may include investments in global equity, global debt and currencies. Defined Benefit Pension Plan Assets - The asset mix of defined benefit pension plans is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investments include, but are not limited to, direct ownership of real estate, oil and gas limited partnerships, securities of the managers’ firms or affiliate firms, and Alliant Energy securities. The allocations shown below exclude market exposure obtained through the overlay management service and cash held at IPL's qualified defined benefit pension plan as a result of a contribution made late in 2022. At December 31, 2022, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 4% Equity securities - U.S. 14% - 61% 33% Equity securities - international 11% - 31% 21% Global asset securities 2% - 11% 5% Fixed income securities 27% - 47% 37% Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. The investment strategy of the Corporate Services 401(h) assets mirrors those of the defined benefit pension plans, which are discussed above. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. At December 31, 2022, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 1% Equity securities - U.S. 0% - 55% 35% Fixed income securities 40% - 100% 64% Fair Value Measurements - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Refer to Note 16 for discussion of levels within the fair value hierarchy. Level 1 items include investments in securities held in registered investment companies and directly held equity securities, which are valued at the closing price reported in the active market in which the securities are traded. Level 2 items include cash and equivalents and fixed income securities. Cash and equivalents include money market fund investments and cash collateral supporting derivative financial instruments. Fixed income securities include corporate and government bonds, which are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Certain investments that are measured at fair value using the net asset value practical expedient have not been classified in the fair value hierarchy. These fair value amounts are included below to reconcile the fair value hierarchy to the respective total plan assets. At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $79 $— $79 $— $35 $— $35 $— Equity securities - U.S. 185 185 — — 256 256 — — Global asset securities 35 35 — — 52 52 — — Fixed income securities 130 30 100 — 191 47 144 — Total assets in fair value hierarchy 429 $250 $179 $— 534 $355 $179 $— Assets measured at net asset value 276 477 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) — (1) Total pension plan assets $706 $1,011 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $62 $— $62 $— $16 $— $16 $— Equity securities - U.S. 83 83 — — 117 117 — — Global asset securities 16 16 — — 24 24 — — Fixed income securities 58 13 45 — 87 21 66 — Total assets in fair value hierarchy 219 $112 $107 $— 244 $162 $82 $— Assets measured at net asset value 124 218 Accrued investment income 1 — Total pension plan assets $344 $462 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $13 $— $13 $— $16 $— $16 $— Equity securities - U.S. 82 82 — — 114 114 — — Global asset securities 16 16 — — 23 23 — — Fixed income securities 57 13 44 — 85 21 64 — Total assets in fair value hierarchy 168 $111 $57 $— 238 $158 $80 $— Assets measured at net asset value 122 212 Accrued investment income 1 — Total pension plan assets $291 $450 At December 31, the fair values of OPEB plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $3 $— $3 $— $5 $— $5 $— Equity securities - U.S. 9 9 — — 11 11 — — Global asset securities 1 1 — — 1 1 — — Fixed income securities 47 46 1 — 60 58 2 — Total assets in fair value hierarchy 60 $56 $4 $— 77 $70 $7 $— Assets measured at net asset value 23 29 Total OPEB plan assets $83 $106 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $1 $— $1 $— $1 $— $1 $— Equity securities - U.S. 5 5 — — 8 8 — — Fixed income securities 34 34 — — 42 42 — — Total assets in fair value hierarchy 40 $39 $1 $— 51 $50 $1 $— Assets measured at net asset value 18 23 Total OPEB plan assets $58 $74 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $— $— $— $— $1 $— $1 $— Equity securities - U.S. 1 1 — — 1 1 — — Fixed income securities 13 13 — — 15 15 — — Total OPEB plan assets $14 $14 $— $— $17 $16 $1 $— For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2022 and 2021. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock directly held by participants represented 10% and 9% of total assets in the 401(k) savings plans at December 31, 2022 and 2021, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 401(k) costs $28 $26 $25 $13 $13 $13 $13 $12 $12 Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Compensation expense $13 $14 $16 $7 $8 $9 $5 $6 $6 Income tax benefits 3 4 4 2 2 2 1 2 2 As of December 31, 2022, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $6 million, $3 million and $2 million, respectively, which is expected to be recognized over a weighted average period of between one year and two years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is recorded in “Other operation and maintenance” in the income statements. As of December 31, 2022, 320,084 shares were included in the calculation of diluted EPS related to the nonvested equity awards. Performance Shares - Equity Awards - Payouts of performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group. Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these performance shares is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a three-year performance period. The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. If minimum performance targets are not met during the performance period, these performance shares are forfeited. Compensation expense is recorded ratably over the performance period based on the fair value of the awards at the grant date. A summary of the performance shares activity, with amounts representing the target number of awards, was as follows: 2022 2021 2020 Shares Weighted Shares Weighted Shares Weighted Nonvested awards, January 1 196,429 $51.59 129,156 $54.63 74,193 $47.44 Granted 74,106 54.45 73,112 46.19 56,204 64.04 Vested (71,101) 47.48 — — — — Forfeited (9,161) 53.99 (5,839) 51.07 (1,241) 50.94 Nonvested awards, December 31 190,273 54.13 196,429 51.59 129,156 54.63 Restricted Stock Units - Equity Awards - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock unit grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these restricted stock units is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on the fair value of the awards on the grant date. A summary of the restricted stock units activity was as follows: 2022 2021 2020 Units Weighted Units Weighted Units Weighted Nonvested units, January 1 217,819 $50.54 146,549 $51.54 89,281 $46.04 Granted 77,122 56.88 80,152 48.65 61,056 59.42 Vested (82,770) 46.08 — — — — Forfeited (13,896) 55.53 (8,882) 49.84 (3,788) 49.01 Nonvested units, December 31 198,275 54.53 217,819 50.54 146,549 51.54 Performance Restricted Stock Units - Equity Awards - Payouts of performance restricted stock units are based upon achievement of certain performance targets during a three-year performance period, which currently includes specified growth of consolidated net income from continuing operations, as well as a diversity metric for the 2022 grants. The actual number of units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of units under each award type. If minimum performance targets are not met during the performance period, these units are forfeited. Performance restricted stock units are to be paid out in shares and are accounted for as equity awards. The fair value of each performance restricted stock unit is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on a probability assessment of payouts for the awards at each reporting period. A summary of the performance restricted stock units activity, with amounts representing the target number of units, was as follows: 2022 2021 2020 Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Nonvested units, January 1 196,429 $50.74 197,463 $47.31 206,065 $41.50 Granted 84,670 57.01 73,112 48.66 56,204 59.37 Vested (71,101) 46.24 (68,307) 38.60 (63,565) 39.12 Forfeited (10,124) 55.92 (5,839) 50.46 (1,241) 49.25 Nonvested units, December 31 199,874 54.74 196,429 50.74 197,463 47.31

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2022
Schedule of Asset Retirement Obligations [Line Items]
Asset Retirement Obligations (AROs)	ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, solar generation, coal yards, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Balance, January 1 $294 $251 $213 $177 $81 $74 Revisions in estimated cash flows 19 50 15 44 4 6 Liabilities settled (48) (17) (39) (13) (9) (4) Liabilities incurred 6 3 — — 6 3 Accretion expense 8 7 6 5 2 2 Balance, December 31 $279 $294 $195 $213 $84 $81
IPL [Member]
Schedule of Asset Retirement Obligations [Line Items]
Asset Retirement Obligations (AROs)	ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, solar generation, coal yards, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Balance, January 1 $294 $251 $213 $177 $81 $74 Revisions in estimated cash flows 19 50 15 44 4 6 Liabilities settled (48) (17) (39) (13) (9) (4) Liabilities incurred 6 3 — — 6 3 Accretion expense 8 7 6 5 2 2 Balance, December 31 $279 $294 $195 $213 $84 $81
WPL [Member]
Schedule of Asset Retirement Obligations [Line Items]
Asset Retirement Obligations (AROs)	ASSET RETIREMENT OBLIGATIONS Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, solar generation, coal yards, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Balance, January 1 $294 $251 $213 $177 $81 $74 Revisions in estimated cash flows 19 50 15 44 4 6 Liabilities settled (48) (17) (39) (13) (9) (4) Liabilities incurred 6 3 — — 6 3 Accretion expense 8 7 6 5 2 2 Balance, December 31 $279 $294 $195 $213 $84 $81

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2022
Derivative [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments were used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Risk policies are maintained that govern the use of such derivative instruments. Derivative instruments were not designated as hedging instruments and included the following: Risk management purpose Type of instrument Mitigate pricing volatility for: Fuel used to supply natural gas-fired EGUs Natural gas swap, options and physical forward contracts (IPL and WPL) Natural gas supplied to retail customers Natural gas swap, options and physical forward contracts (IPL and WPL) Fuel used at coal-fired EGUs Coal physical forward contracts (IPL and WPL) Electric generation and load Electric swap contracts (IPL and WPL) Optimize the value of natural gas pipeline capacity Natural gas physical forward contracts (IPL and WPL) Natural gas swap contracts (IPL) Optimize the value of electric generation Electric swap contracts (IPL and WPL) Manage transmission congestion costs FTRs (IPL and WPL) Manage rail transportation costs Diesel fuel swap contracts (WPL) Notional Amounts - As of December 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 1,132 2023-2025 9,046 2023 224,060 2023-2032 781 2023 IPL 589 2023-2025 3,999 2023 115,237 2023-2030 396 2023 WPL 543 2023 5,047 2023 108,823 2023-2032 385 2023 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Current derivative assets $111 $113 $69 $48 $42 $65 Non-current derivative assets 126 63 69 36 57 27 Current derivative liabilities 59 8 40 4 19 4 Non-current derivative liabilities 20 1 6 — 14 1 In 2022, Alliant Energy’s, IPL’s and WPL’s derivative assets increased primarily as a result of higher natural gas prices. Alliant Energy’s, IPL’s and WPL’s derivative liabilities increased primarily due to new natural gas contracts entered into in 2022 and declining natural gas prices subsequent to the execution of the new contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2022 and 2021, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets at December 31 as follows: Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net 2022 Derivative assets $237 $193 $138 $108 $99 $85 Derivative liabilities 79 35 46 16 33 19 2021 Derivative assets 176 171 84 83 92 88 Derivative liabilities 9 4 4 3 5 1 Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.
IPL [Member]
Derivative [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments were used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Risk policies are maintained that govern the use of such derivative instruments. Derivative instruments were not designated as hedging instruments and included the following: Risk management purpose Type of instrument Mitigate pricing volatility for: Fuel used to supply natural gas-fired EGUs Natural gas swap, options and physical forward contracts (IPL and WPL) Natural gas supplied to retail customers Natural gas swap, options and physical forward contracts (IPL and WPL) Fuel used at coal-fired EGUs Coal physical forward contracts (IPL and WPL) Electric generation and load Electric swap contracts (IPL and WPL) Optimize the value of natural gas pipeline capacity Natural gas physical forward contracts (IPL and WPL) Natural gas swap contracts (IPL) Optimize the value of electric generation Electric swap contracts (IPL and WPL) Manage transmission congestion costs FTRs (IPL and WPL) Manage rail transportation costs Diesel fuel swap contracts (WPL) Notional Amounts - As of December 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 1,132 2023-2025 9,046 2023 224,060 2023-2032 781 2023 IPL 589 2023-2025 3,999 2023 115,237 2023-2030 396 2023 WPL 543 2023 5,047 2023 108,823 2023-2032 385 2023 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Current derivative assets $111 $113 $69 $48 $42 $65 Non-current derivative assets 126 63 69 36 57 27 Current derivative liabilities 59 8 40 4 19 4 Non-current derivative liabilities 20 1 6 — 14 1 In 2022, Alliant Energy’s, IPL’s and WPL’s derivative assets increased primarily as a result of higher natural gas prices. Alliant Energy’s, IPL’s and WPL’s derivative liabilities increased primarily due to new natural gas contracts entered into in 2022 and declining natural gas prices subsequent to the execution of the new contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2022 and 2021, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets at December 31 as follows: Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net 2022 Derivative assets $237 $193 $138 $108 $99 $85 Derivative liabilities 79 35 46 16 33 19 2021 Derivative assets 176 171 84 83 92 88 Derivative liabilities 9 4 4 3 5 1 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 [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments were used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and rail transportation costs. Risk policies are maintained that govern the use of such derivative instruments. Derivative instruments were not designated as hedging instruments and included the following: Risk management purpose Type of instrument Mitigate pricing volatility for: Fuel used to supply natural gas-fired EGUs Natural gas swap, options and physical forward contracts (IPL and WPL) Natural gas supplied to retail customers Natural gas swap, options and physical forward contracts (IPL and WPL) Fuel used at coal-fired EGUs Coal physical forward contracts (IPL and WPL) Electric generation and load Electric swap contracts (IPL and WPL) Optimize the value of natural gas pipeline capacity Natural gas physical forward contracts (IPL and WPL) Natural gas swap contracts (IPL) Optimize the value of electric generation Electric swap contracts (IPL and WPL) Manage transmission congestion costs FTRs (IPL and WPL) Manage rail transportation costs Diesel fuel swap contracts (WPL) Notional Amounts - As of December 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 1,132 2023-2025 9,046 2023 224,060 2023-2032 781 2023 IPL 589 2023-2025 3,999 2023 115,237 2023-2030 396 2023 WPL 543 2023 5,047 2023 108,823 2023-2032 385 2023 Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Current derivative assets $111 $113 $69 $48 $42 $65 Non-current derivative assets 126 63 69 36 57 27 Current derivative liabilities 59 8 40 4 19 4 Non-current derivative liabilities 20 1 6 — 14 1 In 2022, Alliant Energy’s, IPL’s and WPL’s derivative assets increased primarily as a result of higher natural gas prices. Alliant Energy’s, IPL’s and WPL’s derivative liabilities increased primarily due to new natural gas contracts entered into in 2022 and declining natural gas prices subsequent to the execution of the new contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2022 and 2021, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets at December 31 as follows: Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net 2022 Derivative assets $237 $193 $138 $108 $99 $85 Derivative liabilities 79 35 46 16 33 19 2021 Derivative assets 176 171 84 83 92 88 Derivative liabilities 9 4 4 3 5 1 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	12 Months Ended
	Dec. 31, 2022
Fair Value Measurements	FAIR VALUE MEASUREMENTS Valuation Hierarchy - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Level 1 pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Level 2 pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. Level 3 pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. Valuation Techniques - Derivative assets and derivative liabilities - Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. Commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using auction prices and were categorized as Level 3. Refer to Note 15 for additional details of derivative assets and derivative liabilities. Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable program was calculated each reporting date using the cost approach valuation technique. The fair value represents 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 due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 5(b) for additional information regarding deferred proceeds. Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on a discounted cash flow methodology using observable data from comparably traded securities with similar credit profiles, and was substantially classified as Level 2. Refer to Note 9(b) for additional information regarding long-term debt. 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 the related estimated fair values of other financial instruments at December 31 were as follows (in millions): Alliant Energy 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 237 — 206 31 237 176 — 146 30 176 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 79 — 67 12 79 9 — 8 1 9 Long-term debt (incl. current maturities) 8,076 — 7,338 1 7,339 7,368 — 8,329 1 8,330 IPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 138 — 111 27 138 84 — 65 19 84 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 46 — 35 11 46 4 — 3 1 4 Long-term debt 3,646 — 3,228 — 3,228 3,643 — 4,124 — 4,124 WPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $99 $— $95 $4 $99 $92 $— $81 $11 $92 Liabilities and equity: Derivatives 33 — 32 1 33 5 — 5 — 5 Long-term debt (incl. current maturities) 2,770 — 2,542 — 2,542 2,429 — 2,862 — 2,862 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (18) 6 — — Purchases 79 21 — — Sales (2) (1) — — Settlements (a) (69) (26) (29) 26 Ending balance, December 31 $19 $29 $185 $214 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($18) $6 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (12) (3) — — Purchases 58 16 — — Sales (1) (1) — — Settlements (a) (47) (20) (29) 26 Ending balance, December 31 $16 $18 $185 $214 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 December 31 ($13) ($3) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2022 2021 Beginning balance, January 1 $11 $3 Total net gains (losses) included in changes in net assets (realized/unrealized) (6) 9 Purchases 21 5 Sales (1) — Settlements (a) (22) (6) Ending balance, December 31 $3 $11 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($5) $9 (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 derivativ e assets (liabiliti es) at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2022 ($10) $29 ($9) $25 ($1) $4 2021 9 20 8 10 1 10
IPL [Member]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Valuation Hierarchy - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Level 1 pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Level 2 pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. Level 3 pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. Valuation Techniques - Derivative assets and derivative liabilities - Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. Commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using auction prices and were categorized as Level 3. Refer to Note 15 for additional details of derivative assets and derivative liabilities. Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable program was calculated each reporting date using the cost approach valuation technique. The fair value represents 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 due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 5(b) for additional information regarding deferred proceeds. Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on a discounted cash flow methodology using observable data from comparably traded securities with similar credit profiles, and was substantially classified as Level 2. Refer to Note 9(b) for additional information regarding long-term debt. 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 the related estimated fair values of other financial instruments at December 31 were as follows (in millions): Alliant Energy 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 237 — 206 31 237 176 — 146 30 176 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 79 — 67 12 79 9 — 8 1 9 Long-term debt (incl. current maturities) 8,076 — 7,338 1 7,339 7,368 — 8,329 1 8,330 IPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 138 — 111 27 138 84 — 65 19 84 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 46 — 35 11 46 4 — 3 1 4 Long-term debt 3,646 — 3,228 — 3,228 3,643 — 4,124 — 4,124 WPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $99 $— $95 $4 $99 $92 $— $81 $11 $92 Liabilities and equity: Derivatives 33 — 32 1 33 5 — 5 — 5 Long-term debt (incl. current maturities) 2,770 — 2,542 — 2,542 2,429 — 2,862 — 2,862 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (18) 6 — — Purchases 79 21 — — Sales (2) (1) — — Settlements (a) (69) (26) (29) 26 Ending balance, December 31 $19 $29 $185 $214 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($18) $6 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (12) (3) — — Purchases 58 16 — — Sales (1) (1) — — Settlements (a) (47) (20) (29) 26 Ending balance, December 31 $16 $18 $185 $214 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 December 31 ($13) ($3) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2022 2021 Beginning balance, January 1 $11 $3 Total net gains (losses) included in changes in net assets (realized/unrealized) (6) 9 Purchases 21 5 Sales (1) — Settlements (a) (22) (6) Ending balance, December 31 $3 $11 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($5) $9 (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 derivativ e assets (liabiliti es) at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2022 ($10) $29 ($9) $25 ($1) $4 2021 9 20 8 10 1 10
WPL [Member]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Valuation Hierarchy - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Level 1 pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Level 2 pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. Level 3 pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. Valuation Techniques - Derivative assets and derivative liabilities - Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. Commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using auction prices and were categorized as Level 3. Refer to Note 15 for additional details of derivative assets and derivative liabilities. Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable program was calculated each reporting date using the cost approach valuation technique. The fair value represents 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 due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 5(b) for additional information regarding deferred proceeds. Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on a discounted cash flow methodology using observable data from comparably traded securities with similar credit profiles, and was substantially classified as Level 2. Refer to Note 9(b) for additional information regarding long-term debt. 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 the related estimated fair values of other financial instruments at December 31 were as follows (in millions): Alliant Energy 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 237 — 206 31 237 176 — 146 30 176 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 79 — 67 12 79 9 — 8 1 9 Long-term debt (incl. current maturities) 8,076 — 7,338 1 7,339 7,368 — 8,329 1 8,330 IPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 138 — 111 27 138 84 — 65 19 84 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 46 — 35 11 46 4 — 3 1 4 Long-term debt 3,646 — 3,228 — 3,228 3,643 — 4,124 — 4,124 WPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $99 $— $95 $4 $99 $92 $— $81 $11 $92 Liabilities and equity: Derivatives 33 — 32 1 33 5 — 5 — 5 Long-term debt (incl. current maturities) 2,770 — 2,542 — 2,542 2,429 — 2,862 — 2,862 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (18) 6 — — Purchases 79 21 — — Sales (2) (1) — — Settlements (a) (69) (26) (29) 26 Ending balance, December 31 $19 $29 $185 $214 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($18) $6 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (12) (3) — — Purchases 58 16 — — Sales (1) (1) — — Settlements (a) (47) (20) (29) 26 Ending balance, December 31 $16 $18 $185 $214 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 December 31 ($13) ($3) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2022 2021 Beginning balance, January 1 $11 $3 Total net gains (losses) included in changes in net assets (realized/unrealized) (6) 9 Purchases 21 5 Sales (1) — Settlements (a) (22) (6) Ending balance, December 31 $3 $11 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($5) $9 (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 derivativ e assets (liabiliti es) at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2022 ($10) $29 ($9) $25 ($1) $4 2021 9 20 8 10 1 10

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including WPL’s expansion of solar generation. At December 31, 2022, Alliant Energy’s and WPL’s minimum future commitments in 2023 for these projects were $184 million and $180 million, respectively.(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 December 31, 2022, the related minimum future commitments were as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 Thereafter Total Natural gas $558 $297 $199 $136 $85 $209 $1,484 Coal 89 64 22 3 3 — 181 Other (a) 72 12 9 9 2 24 128 $719 $373 $230 $148 $90 $233 $1,793 IPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $319 $167 $85 $48 $36 $39 $694 Coal 45 26 20 3 3 — 97 Other (a) 28 2 2 2 2 22 58 $392 $195 $107 $53 $41 $61 $849 WPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $239 $130 $114 $88 $49 $170 $790 Coal 44 38 2 — — — 84 Other (a) 28 1 1 1 — — 31 $311 $169 $117 $89 $49 $170 $905 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2022. 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 December 31, 2022, 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 December 31, 2022 and 2021, a liability of $5 million is recorded in “Other liabilities” on Alliant Energy’s balance sheets for expected credit losses related to the contingent obligations that are in the scope of these guarantees. 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 December 31, 2022 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of December 31, 2022 and 2021. Manufactured Gas Plant 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 December 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $9 - $25 $6 - $19 Current and non-current environmental liabilities $11 $8 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 CAA 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: CSAPR, Effluent Limitation Guidelines, CCR Rule, and various legislation and EPA regulations to monitor and regulate the emission of GHG, including the CAA. Alliant Energy, IPL and WPL are subject to credit risk related to the ability of counterparties to meet their contractual payment obligations or the potential non-performance of counterparties to deliver contracted commodities and other goods or services at the contracted price. Credit policies are maintained to mitigate credit risk. These credit policies include evaluation of the financial condition of certain counterparties, use of credit risk-related contingent provisions in certain agreements that require credit support from counterparties not meeting specific criteria, diversification of counterparties to reduce concentrations of credit risk and the use of standardized agreements that facilitate the netting of cash flows associated with certain counterparties. Based on these credit policies and counterparty diversification, as well as utility cost recovery mechanisms, it is unlikely that counterparty non-performance would have a material effect on financial condition or results of operations. However, there is no assurance that these items will protect against all losses from counterparty non-performance. Refer to Notes 5(a) and 15 for details of allowances for expected credit losses and credit risk-related contingent features, respectively.
IPL [Member]
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES(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 December 31, 2022, the related minimum future commitments were as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 Thereafter Total Natural gas $558 $297 $199 $136 $85 $209 $1,484 Coal 89 64 22 3 3 — 181 Other (a) 72 12 9 9 2 24 128 $719 $373 $230 $148 $90 $233 $1,793 IPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $319 $167 $85 $48 $36 $39 $694 Coal 45 26 20 3 3 — 97 Other (a) 28 2 2 2 2 22 58 $392 $195 $107 $53 $41 $61 $849 WPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $239 $130 $114 $88 $49 $170 $790 Coal 44 38 2 — — — 84 Other (a) 28 1 1 1 — — 31 $311 $169 $117 $89 $49 $170 $905 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2022. Manufactured Gas Plant 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 December 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $9 - $25 $6 - $19 Current and non-current environmental liabilities $11 $8 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 CAA 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: CSAPR, Effluent Limitation Guidelines, CCR Rule, and various legislation and EPA regulations to monitor and regulate the emission of GHG, including the CAA. Alliant Energy, IPL and WPL are subject to credit risk related to the ability of counterparties to meet their contractual payment obligations or the potential non-performance of counterparties to deliver contracted commodities and other goods or services at the contracted price. Credit policies are maintained to mitigate credit risk. These credit policies include evaluation of the financial condition of certain counterparties, use of credit risk-related contingent provisions in certain agreements that require credit support from counterparties not meeting specific criteria, diversification of counterparties to reduce concentrations of credit risk and the use of standardized agreements that facilitate the netting of cash flows associated with certain counterparties. Based on these credit policies and counterparty diversification, as well as utility cost recovery mechanisms, it is unlikely that counterparty non-performance would have a material effect on financial condition or results of operations. However, there is no assurance that these items will protect against all losses from counterparty non-performance. Refer to Notes 5(a) and 15 for details of allowances for expected credit losses and credit risk-related contingent features, respectively.
WPL [Member]
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including WPL’s expansion of solar generation. At December 31, 2022, Alliant Energy’s and WPL’s minimum future commitments in 2023 for these projects were $184 million and $180 million, respectively.(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 December 31, 2022, the related minimum future commitments were as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 Thereafter Total Natural gas $558 $297 $199 $136 $85 $209 $1,484 Coal 89 64 22 3 3 — 181 Other (a) 72 12 9 9 2 24 128 $719 $373 $230 $148 $90 $233 $1,793 IPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $319 $167 $85 $48 $36 $39 $694 Coal 45 26 20 3 3 — 97 Other (a) 28 2 2 2 2 22 58 $392 $195 $107 $53 $41 $61 $849 WPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $239 $130 $114 $88 $49 $170 $790 Coal 44 38 2 — — — 84 Other (a) 28 1 1 1 — — 31 $311 $169 $117 $89 $49 $170 $905 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2022. Manufactured Gas Plant 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 December 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $9 - $25 $6 - $19 Current and non-current environmental liabilities $11 $8 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 CAA 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: CSAPR, Effluent Limitation Guidelines, CCR Rule, and various legislation and EPA regulations to monitor and regulate the emission of GHG, including the CAA. Alliant Energy, IPL and WPL are subject to credit risk related to the ability of counterparties to meet their contractual payment obligations or the potential non-performance of counterparties to deliver contracted commodities and other goods or services at the contracted price. Credit policies are maintained to mitigate credit risk. These credit policies include evaluation of the financial condition of certain counterparties, use of credit risk-related contingent provisions in certain agreements that require credit support from counterparties not meeting specific criteria, diversification of counterparties to reduce concentrations of credit risk and the use of standardized agreements that facilitate the netting of cash flows associated with certain counterparties. Based on these credit policies and counterparty diversification, as well as utility cost recovery mechanisms, it is unlikely that counterparty non-performance would have a material effect on financial condition or results of operations. However, there is no assurance that these items will protect against all losses from counterparty non-performance. Refer to Notes 5(a) and 15 for details of allowances for expected credit losses and credit risk-related contingent features, respectively.

Segments Of Business

Segments Of Business	12 Months Ended
	Dec. 31, 2022
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2022 are: • Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.” • ATC Holdings, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s interest in ATC Holdings, Travero, a non-utility wind farm, corporate venture investments, the Sheboygan Falls Energy Facility and other non-utility holdings. Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions): ATC Holdings, Utility Non-utility, Alliant Energy 2022 Electric Gas Other Total Parent and Other Consolidated Revenues $3,421 $642 $49 $4,112 $93 $4,205 Depreciation and amortization 601 56 7 664 7 671 Operating income 805 97 3 905 23 928 Interest expense 269 56 325 Equity income from unconsolidated investments, net (1) — — (1) (50) (51) Income taxes 16 6 22 Net income attributable to Alliant Energy common shareowners 675 11 686 Total assets 16,571 1,631 860 19,062 1,101 20,163 Investments in equity method subsidiaries 20 — — 20 522 542 Construction and acquisition expenditures 1,318 74 — 1,392 92 1,484 ATC Holdings, Utility Non-utility, Alliant Energy 2021 Electric Gas Other Total Parent and Other Consolidated Revenues $3,081 $456 $49 $3,586 $83 $3,669 Depreciation and amortization 591 54 6 651 6 657 Operating income (loss) 716 63 (11) 768 27 795 Interest expense 244 33 277 Equity income from unconsolidated investments, net (2) — — (2) (60) (62) Income tax expense (benefit) (87) 13 (74) Net income attributable to Alliant Energy common shareowners 618 41 659 Total assets 14,924 1,487 1,103 17,514 1,039 18,553 Investments in equity method subsidiaries 17 — — 17 491 508 Construction and acquisition expenditures 980 90 — 1,070 99 1,169 ATC Holdings, Utility Non-utility, Alliant Energy 2020 Electric Gas Other Total Parent and Other Consolidated Revenues $2,920 $373 $49 $3,342 $74 $3,416 Depreciation and amortization 556 49 5 610 5 615 Operating income (loss) 643 74 (1) 716 24 740 Interest expense 243 32 275 Equity income from unconsolidated investments, net (2) — — (2) (59) (61) Income tax expense (benefit) (66) 9 (57) Net income attributable to Alliant Energy common shareowners 573 41 614 Total assets 14,358 1,413 990 16,761 949 17,710 Investments in equity method subsidiaries 11 — — 11 465 476 Construction and acquisition expenditures 1,109 182 2 1,293 73 1,366 IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,859 $351 $46 $2,256 Depreciation and amortization 342 32 7 381 Operating income 397 53 3 453 Interest expense 148 Income tax benefit (50) Net income available for common stock 360 Total assets 8,686 872 517 10,075 Construction and acquisition expenditures 336 36 — 372 2021 Electric Gas Other Total Revenues $1,752 $265 $46 $2,063 Depreciation and amortization 338 31 6 375 Operating income (loss) 420 43 (3) 460 Interest expense 139 Income tax benefit (36) Net income available for common stock 350 Total assets 8,602 819 575 9,996 Construction and acquisition expenditures 342 42 — 384 2020 Electric Gas Other Total Revenues $1,695 $208 $44 $1,947 Depreciation and amortization 321 30 5 356 Operating income 358 50 2 410 Interest expense 139 Income tax benefit (47) Net income available for common stock 324 Total assets 8,518 766 565 9,849 Construction and acquisition expenditures 626 59 2 687 WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,562 $291 $3 $1,856 Depreciation and amortization 259 24 — 283 Operating income 408 44 — 452 Interest expense 121 Income taxes 66 Net income 315 Total assets 7,885 759 343 8,987 Construction and acquisition expenditures 982 38 — 1,020 2021 Electric Gas Other Total Revenues $1,329 $191 $3 $1,523 Depreciation and amortization 253 23 — 276 Operating income (loss) 296 20 (8) 308 Interest expense 105 Income tax benefit (51) Net income 268 Total assets 6,322 668 528 7,518 Construction and acquisition expenditures 638 48 — 686 2020 Electric Gas Other Total Revenues $1,225 $165 $5 $1,395 Depreciation and amortization 235 19 — 254 Operating income (loss) 285 24 (3) 306 Interest expense 104 Income tax benefit (19) Net income 249 Total assets 5,840 647 425 6,912 Construction and acquisition expenditures 483 123 — 606
IPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2022 are: • Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.” • ATC Holdings, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s interest in ATC Holdings, Travero, a non-utility wind farm, corporate venture investments, the Sheboygan Falls Energy Facility and other non-utility holdings. Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions): ATC Holdings, Utility Non-utility, Alliant Energy 2022 Electric Gas Other Total Parent and Other Consolidated Revenues $3,421 $642 $49 $4,112 $93 $4,205 Depreciation and amortization 601 56 7 664 7 671 Operating income 805 97 3 905 23 928 Interest expense 269 56 325 Equity income from unconsolidated investments, net (1) — — (1) (50) (51) Income taxes 16 6 22 Net income attributable to Alliant Energy common shareowners 675 11 686 Total assets 16,571 1,631 860 19,062 1,101 20,163 Investments in equity method subsidiaries 20 — — 20 522 542 Construction and acquisition expenditures 1,318 74 — 1,392 92 1,484 ATC Holdings, Utility Non-utility, Alliant Energy 2021 Electric Gas Other Total Parent and Other Consolidated Revenues $3,081 $456 $49 $3,586 $83 $3,669 Depreciation and amortization 591 54 6 651 6 657 Operating income (loss) 716 63 (11) 768 27 795 Interest expense 244 33 277 Equity income from unconsolidated investments, net (2) — — (2) (60) (62) Income tax expense (benefit) (87) 13 (74) Net income attributable to Alliant Energy common shareowners 618 41 659 Total assets 14,924 1,487 1,103 17,514 1,039 18,553 Investments in equity method subsidiaries 17 — — 17 491 508 Construction and acquisition expenditures 980 90 — 1,070 99 1,169 ATC Holdings, Utility Non-utility, Alliant Energy 2020 Electric Gas Other Total Parent and Other Consolidated Revenues $2,920 $373 $49 $3,342 $74 $3,416 Depreciation and amortization 556 49 5 610 5 615 Operating income (loss) 643 74 (1) 716 24 740 Interest expense 243 32 275 Equity income from unconsolidated investments, net (2) — — (2) (59) (61) Income tax expense (benefit) (66) 9 (57) Net income attributable to Alliant Energy common shareowners 573 41 614 Total assets 14,358 1,413 990 16,761 949 17,710 Investments in equity method subsidiaries 11 — — 11 465 476 Construction and acquisition expenditures 1,109 182 2 1,293 73 1,366 IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,859 $351 $46 $2,256 Depreciation and amortization 342 32 7 381 Operating income 397 53 3 453 Interest expense 148 Income tax benefit (50) Net income available for common stock 360 Total assets 8,686 872 517 10,075 Construction and acquisition expenditures 336 36 — 372 2021 Electric Gas Other Total Revenues $1,752 $265 $46 $2,063 Depreciation and amortization 338 31 6 375 Operating income (loss) 420 43 (3) 460 Interest expense 139 Income tax benefit (36) Net income available for common stock 350 Total assets 8,602 819 575 9,996 Construction and acquisition expenditures 342 42 — 384 2020 Electric Gas Other Total Revenues $1,695 $208 $44 $1,947 Depreciation and amortization 321 30 5 356 Operating income 358 50 2 410 Interest expense 139 Income tax benefit (47) Net income available for common stock 324 Total assets 8,518 766 565 9,849 Construction and acquisition expenditures 626 59 2 687 WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,562 $291 $3 $1,856 Depreciation and amortization 259 24 — 283 Operating income 408 44 — 452 Interest expense 121 Income taxes 66 Net income 315 Total assets 7,885 759 343 8,987 Construction and acquisition expenditures 982 38 — 1,020 2021 Electric Gas Other Total Revenues $1,329 $191 $3 $1,523 Depreciation and amortization 253 23 — 276 Operating income (loss) 296 20 (8) 308 Interest expense 105 Income tax benefit (51) Net income 268 Total assets 6,322 668 528 7,518 Construction and acquisition expenditures 638 48 — 686 2020 Electric Gas Other Total Revenues $1,225 $165 $5 $1,395 Depreciation and amortization 235 19 — 254 Operating income (loss) 285 24 (3) 306 Interest expense 104 Income tax benefit (19) Net income 249 Total assets 5,840 647 425 6,912 Construction and acquisition expenditures 483 123 — 606
WPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2022 are: • Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.” • ATC Holdings, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s interest in ATC Holdings, Travero, a non-utility wind farm, corporate venture investments, the Sheboygan Falls Energy Facility and other non-utility holdings. Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions): ATC Holdings, Utility Non-utility, Alliant Energy 2022 Electric Gas Other Total Parent and Other Consolidated Revenues $3,421 $642 $49 $4,112 $93 $4,205 Depreciation and amortization 601 56 7 664 7 671 Operating income 805 97 3 905 23 928 Interest expense 269 56 325 Equity income from unconsolidated investments, net (1) — — (1) (50) (51) Income taxes 16 6 22 Net income attributable to Alliant Energy common shareowners 675 11 686 Total assets 16,571 1,631 860 19,062 1,101 20,163 Investments in equity method subsidiaries 20 — — 20 522 542 Construction and acquisition expenditures 1,318 74 — 1,392 92 1,484 ATC Holdings, Utility Non-utility, Alliant Energy 2021 Electric Gas Other Total Parent and Other Consolidated Revenues $3,081 $456 $49 $3,586 $83 $3,669 Depreciation and amortization 591 54 6 651 6 657 Operating income (loss) 716 63 (11) 768 27 795 Interest expense 244 33 277 Equity income from unconsolidated investments, net (2) — — (2) (60) (62) Income tax expense (benefit) (87) 13 (74) Net income attributable to Alliant Energy common shareowners 618 41 659 Total assets 14,924 1,487 1,103 17,514 1,039 18,553 Investments in equity method subsidiaries 17 — — 17 491 508 Construction and acquisition expenditures 980 90 — 1,070 99 1,169 ATC Holdings, Utility Non-utility, Alliant Energy 2020 Electric Gas Other Total Parent and Other Consolidated Revenues $2,920 $373 $49 $3,342 $74 $3,416 Depreciation and amortization 556 49 5 610 5 615 Operating income (loss) 643 74 (1) 716 24 740 Interest expense 243 32 275 Equity income from unconsolidated investments, net (2) — — (2) (59) (61) Income tax expense (benefit) (66) 9 (57) Net income attributable to Alliant Energy common shareowners 573 41 614 Total assets 14,358 1,413 990 16,761 949 17,710 Investments in equity method subsidiaries 11 — — 11 465 476 Construction and acquisition expenditures 1,109 182 2 1,293 73 1,366 IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,859 $351 $46 $2,256 Depreciation and amortization 342 32 7 381 Operating income 397 53 3 453 Interest expense 148 Income tax benefit (50) Net income available for common stock 360 Total assets 8,686 872 517 10,075 Construction and acquisition expenditures 336 36 — 372 2021 Electric Gas Other Total Revenues $1,752 $265 $46 $2,063 Depreciation and amortization 338 31 6 375 Operating income (loss) 420 43 (3) 460 Interest expense 139 Income tax benefit (36) Net income available for common stock 350 Total assets 8,602 819 575 9,996 Construction and acquisition expenditures 342 42 — 384 2020 Electric Gas Other Total Revenues $1,695 $208 $44 $1,947 Depreciation and amortization 321 30 5 356 Operating income 358 50 2 410 Interest expense 139 Income tax benefit (47) Net income available for common stock 324 Total assets 8,518 766 565 9,849 Construction and acquisition expenditures 626 59 2 687 WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,562 $291 $3 $1,856 Depreciation and amortization 259 24 — 283 Operating income 408 44 — 452 Interest expense 121 Income taxes 66 Net income 315 Total assets 7,885 759 343 8,987 Construction and acquisition expenditures 982 38 — 1,020 2021 Electric Gas Other Total Revenues $1,329 $191 $3 $1,523 Depreciation and amortization 253 23 — 276 Operating income (loss) 296 20 (8) 308 Interest expense 105 Income tax benefit (51) Net income 268 Total assets 6,322 668 528 7,518 Construction and acquisition expenditures 638 48 — 686 2020 Electric Gas Other Total Revenues $1,225 $165 $5 $1,395 Depreciation and amortization 235 19 — 254 Operating income (loss) 285 24 (3) 306 Interest expense 104 Income tax benefit (19) Net income 249 Total assets 5,840 647 425 6,912 Construction and acquisition expenditures 483 123 — 606

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2022
Related Party Transaction [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 were as follows (in millions): IPL WPL 2022 2021 2020 2022 2021 2020 Corporate Services billings $181 $180 $176 $155 $154 $142 Sales credited 19 22 35 74 23 3 Purchases billed 435 441 329 174 116 108 As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2022 2021 IPL $103 $110 WPL 56 83 ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties were as follows (in millions): 2022 2021 2020 ATC billings to WPL $140 $122 $108 WPL billings to ATC 18 18 10 As of December 31, 2022 and 2021, WPL owed ATC net amounts of $10 million and $10 million, respectively. In 2020, WPL received $46 million from ATC related to construction deposits WPL previously provided ATC for transmission network upgrades for West Riverside, which is substantially recorded in “Other” in Alliant Energy’s and WPL’s cash flows from investing activities. WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 10 for discussion of WPL’s Sheboygan Falls Energy Facility lease.
IPL [Member]
Related Party Transaction [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 were as follows (in millions): IPL WPL 2022 2021 2020 2022 2021 2020 Corporate Services billings $181 $180 $176 $155 $154 $142 Sales credited 19 22 35 74 23 3 Purchases billed 435 441 329 174 116 108 As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2022 2021 IPL $103 $110 WPL 56 83
WPL [Member]
Related Party Transaction [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 were as follows (in millions): IPL WPL 2022 2021 2020 2022 2021 2020 Corporate Services billings $181 $180 $176 $155 $154 $142 Sales credited 19 22 35 74 23 3 Purchases billed 435 441 329 174 116 108 As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2022 2021 IPL $103 $110 WPL 56 83 ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties were as follows (in millions): 2022 2021 2020 ATC billings to WPL $140 $122 $108 WPL billings to ATC 18 18 10 As of December 31, 2022 and 2021, WPL owed ATC net amounts of $10 million and $10 million, respectively. In 2020, WPL received $46 million from ATC related to construction deposits WPL previously provided ATC for transmission network upgrades for West Riverside, which is substantially recorded in “Other” in Alliant Energy’s and WPL’s cash flows from investing activities. WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 10 for discussion of WPL’s Sheboygan Falls Energy Facility lease.

Condensed Parent Company Financ

Condensed Parent Company Financial Statements	12 Months Ended
	Dec. 31, 2022
Condensed Financial Information Disclosure [Abstract]
Condensed Parent Company Financial Statements	SCHEDULE I - CONDENSED PARENT COMPANY FINANCIAL STATEMENTS ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF INCOME 2022 2021 2020 (in millions) Operating expenses $9 $5 $7 Operating loss (9) (5) (7) Other (income) and deductions: Equity earnings from consolidated subsidiaries (707) (664) (625) Interest expense 6 1 2 Other 1 1 4 Total other (income) and deductions (700) (662) (619) Income before income taxes 691 657 612 Income tax expense (benefit) 2 (5) (4) Net income $689 $662 $616 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) December 31, CONDENSED BALANCE SHEETS 2022 2021 (in millions) ASSETS Current assets: Notes receivable from affiliated companies $65 $16 Other 1 5 Total current assets 66 21 Investments: Investments in consolidated subsidiaries 7,801 7,061 Other 2 2 Total investments 7,803 7,063 Other assets 97 96 Total assets $7,966 $7,180 LIABILITIES AND EQUITY Current liabilities: Commercial paper $352 $279 Notes payable to affiliated companies 1,318 900 Other 10 4 Total current liabilities 1,680 1,183 Other liabilities 1 2 Common equity: Common stock and additional paid-in capital 2,780 2,752 Retained earnings 3,518 3,255 Shares in deferred compensation trust (13) (12) Total common equity 6,285 5,995 Total liabilities and equity $7,966 $7,180 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF CASH FLOWS 2022 2021 2020 (in millions) Net cash flows from operating activities $492 $494 $396 Cash flows used for investing activities: Capital contributions to consolidated subsidiaries (530) (295) (429) Net change in notes receivable from and payable to affiliates 369 (21) 201 Dividends from consolidated subsidiaries in excess of equity earnings — 50 — Net cash flows used for investing activities (161) (266) (228) Cash flows used for financing activities: Common stock dividends (428) (403) (377) Proceeds from issuance of common stock, net 25 28 247 Net change in commercial paper 73 147 (37) Other (1) — (1) Net cash flows used for financing activities (331) (228) (168) Net increase (decrease) in cash, cash equivalents and restricted cash — — — Cash, cash equivalents and restricted cash at beginning of period — — — Cash, cash equivalents and restricted cash at end of period $— $— $— Supplemental cash flows information: Cash (paid) refunded during the period for: Interest ($6) ($1) ($2) Income taxes, net $15 $4 $10 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) NOTES TO CONDENSED FINANCIAL STATEMENTS Pursuant to rules and regulations of the SEC, the Condensed Financial Statements of Alliant Energy Corporation (Parent Company Only) do not reflect all of the information and notes normally included with financial statements prepared in accordance with GAAP. Therefore, these Condensed Financial Statements should be read in conjunction with the Financial Statements and related Notes included in the combined 2022 Form 10-K, Part II, Item 8 , which is incorporated herein by reference. In the Condensed Financial Statements of Alliant Energy Corporation (Parent Company Only), investments in subsidiaries are accounted for using the equity method.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts And Reserves	12 Months Ended
	Dec. 31, 2022
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation and Qualifying Accounts And Reserves	SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES Additions Balance, Charged to Charged to Other Balance, Description January 1 Expense Accounts (a) Deductions (b) December 31 (in millions) Valuation and Qualifying Accounts Which are Deducted in the Balance Sheet from the Assets to Which They Apply: Accumulated Provision for Uncollectible Accounts: Alliant Energy (c) Year ended December 31, 2022 $11 $17 $— $21 $7 Year ended December 31, 2021 18 12 — 19 11 Year ended December 31, 2020 7 25 9 23 18 IPL (c) Year ended December 31, 2022 $1 $7 $— $8 $— Year ended December 31, 2021 1 6 — 6 1 Year ended December 31, 2020 1 18 — 18 1 WPL Year ended December 31, 2022 $10 $10 $— $13 $7 Year ended December 31, 2021 17 6 — 13 10 Year ended December 31, 2020 6 7 9 5 17 Note: The above provisions relate to various customer, notes and other receivable balances included in various line items on the respective balance sheets. (a) Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets. (b) Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off. (c) Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.
IPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation and Qualifying Accounts And Reserves	SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES Additions Balance, Charged to Charged to Other Balance, Description January 1 Expense Accounts (a) Deductions (b) December 31 (in millions) Valuation and Qualifying Accounts Which are Deducted in the Balance Sheet from the Assets to Which They Apply: Accumulated Provision for Uncollectible Accounts: Alliant Energy (c) Year ended December 31, 2022 $11 $17 $— $21 $7 Year ended December 31, 2021 18 12 — 19 11 Year ended December 31, 2020 7 25 9 23 18 IPL (c) Year ended December 31, 2022 $1 $7 $— $8 $— Year ended December 31, 2021 1 6 — 6 1 Year ended December 31, 2020 1 18 — 18 1 WPL Year ended December 31, 2022 $10 $10 $— $13 $7 Year ended December 31, 2021 17 6 — 13 10 Year ended December 31, 2020 6 7 9 5 17 Note: The above provisions relate to various customer, notes and other receivable balances included in various line items on the respective balance sheets. (a) Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets. (b) Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off. (c) Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.
WPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation and Qualifying Accounts And Reserves	SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES Additions Balance, Charged to Charged to Other Balance, Description January 1 Expense Accounts (a) Deductions (b) December 31 (in millions) Valuation and Qualifying Accounts Which are Deducted in the Balance Sheet from the Assets to Which They Apply: Accumulated Provision for Uncollectible Accounts: Alliant Energy (c) Year ended December 31, 2022 $11 $17 $— $21 $7 Year ended December 31, 2021 18 12 — 19 11 Year ended December 31, 2020 7 25 9 23 18 IPL (c) Year ended December 31, 2022 $1 $7 $— $8 $— Year ended December 31, 2021 1 6 — 6 1 Year ended December 31, 2020 1 18 — 18 1 WPL Year ended December 31, 2022 $10 $10 $— $13 $7 Year ended December 31, 2021 17 6 — 13 10 Year ended December 31, 2020 6 7 9 5 17 Note: The above provisions relate to various customer, notes and other receivable balances included in various line items on the respective balance sheets. (a) Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets. (b) Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off. (c) Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
General, Basis of Presentation	The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method.All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes.
General, Basis of Accounting	The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction.
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.
General, Use of Estimates	The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Regulatory Assets and Regulatory Liabilities	Alliant Energy, IPL and WPL are subject to regulation by FERC and various state regulatory commissions. As a result, Alliant Energy, IPL and WPL are subject to GAAP provisions for regulated operations, which provide that rate-regulated public utilities record certain costs and credits allowed in the rate-making process in different periods than for non-utility entities. Regulatory assets generally represent incurred costs that have been deferred as such costs are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the related costs have not yet been incurred. Amounts recorded as regulatory assets or regulatory liabilities are generally recognized in the income statements at the time they are reflected in rates.
Income Taxes	The liability method of accounting is followed for deferred taxes, which requires the establishment of deferred tax assets and liabilities, as appropriate, for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state apportionment. Changes in deferred tax assets and liabilities associated with certain property-related differences at IPL are accounted for differently than other subsidiaries of Alliant Energy due to rate-making practices in Iowa. Rate-making practices in Iowa do not allow the impact of certain deferred tax expenses (benefits) to be included in the determination of retail rates. Based on these rate-making practices, deferred tax expense (benefit) related to these property-related differences at IPL is not recorded in the income statement but instead recorded to regulatory assets or regulatory liabilities until these temporary differences reverse. In Wisconsin, the PSCW allows rate recovery of deferred tax expense on all temporary differences. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Federal Tax Reform repealed corporate federal alternative minimum tax and allowed unutilized alternative minimum tax credits to be refunded over four tax years beginning with the U.S. federal tax return for calendar year 2018. Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, Alliant Energy received the remaining alternative minimum tax credits refunds in 2020. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the modified separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). The difference in the income taxes recorded for IPL and WPL under the modified separate return method compared to the income taxes recorded on a separate return basis was not material in 2022, 2021 and 2020.
Cash, Cash Equivalents and Restricted Cash	Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days. At December 31, 2022 and 2021, Alliant Energy’s restricted cash related to requirements in Sheboygan Power, LLC’s debt agreement.
Property, Plant and Equipment	Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements.
Depreciation	IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023.
AFUDC	AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3% In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs.
Revenue Recognition	Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the end of each customer’s last billing period. The unbilled component is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2022, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed.
Utility Cost Recovery Mechanisms	Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.
Financial Instruments	Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement.
Asset Impairments	Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value.
Asset Retirement Obligations	The fair value of a legal obligation associated with the retirement of an asset is recorded as a liability when an asset is placed in service, when a legal obligation is subsequently identified or when sufficient information becomes available to determine a reasonable estimate of the fair value of future retirement costs. When an ARO is recorded as a liability, an equivalent amount is added to the asset cost. The fair value of AROs at inception is determined using discounted cash flows analyses. The liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset. Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory assets on the balance sheets. Revisions in estimated cash flows for IPL’s and WPL’s regulated operations are recorded as an increase or decrease to the ARO liability, with an offset to the asset cost, unless the asset is already retired and then the offset is recorded to regulatory assets or regulatory liabilities on the balance sheets. Upon regulatory approval to recover IPL’s AROs expenditures, its regulatory assets are amortized to depreciation and amortization expenses in Alliant Energy’s and IPL’s income statements over the same time period the ARO expenditures are recovered from IPL’s customers. WPL’s regulatory assets related to AROs are recovered as a component of depreciation rates pursuant to PSCW and FERC orders. Upon settlement of the ARO liability, an entity settles the obligation for its recorded amount or incurs a gain or loss. Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the balance sheets.
Debt Issuance and Retirement Costs	Debt issuance costs and debt premiums or discounts are presented on the balance sheets as a direct adjustment to the carrying amount of the related debt liability, and are deferred and amortized over the expected life of each debt issue, considering maturity dates and, if applicable, redemption rights held by others. Alliant Energy’s non-utility businesses and Corporate Services record to interest expense in the period of retirement any unamortized debt issuance costs and debt premiums or discounts on debt retired early.
Current Expected Credit Losses Estimates	Current expected credit losses are estimated for trade and other receivables and credit exposures on guarantees of the performance by third parties. The current expected credit losses for short-term trade receivables are based on estimates of losses resulting from the inability of customers to make required payments. The methodology used to estimate losses is based on historical write-offs, regional economic conditions, significant events that could impact collectability, such as impacts related to COVID-19, significant weather related matters including the derecho windstorm and related regulatory actions, and forecasted changes to the accounts receivable aging portfolio and write-offs. The current expected credit losses related to guarantees of the performance by third parties are estimated using both quantitative and qualitative information, which utilizes potential outcomes in a range of possible estimated amounts. In 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables, certain other assets and off-balance sheet credit exposures. Alliant Energy, IPL and WPL adopted this standard on January 1, 2020 using a modified retrospective method of adoption, which required cumulative effect adjustments to retained earnings on January 1, 2020. IPL and WPL did not record a cumulative effect adjustment to retained earnings and Alliant Energy recorded a pre-tax $12 million (after-tax $9 million) cumulative effect adjustment to decrease retained earnings related to Alliant Energy’s guarantees in the partnership obligations of an affiliate of Whiting Petroleum (refer to Note 17(d) for further discussion). This adjustment is included in “Adoption of new accounting standard” in Alliant Energy’s equity statement for 2020.
Variable Interest Entities	An entity is considered a VIE if its equity investors do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties, the entity is structured with disproportionate voting rights and substantially all of the entity’s activities are conducted on behalf of the investor with disproportionately fewer voting rights, or its equity investors lack any of the following characteristics: (1) power, through voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb expected losses of the entity; or (3) the right to receive expected benefits of the entity. The primary beneficiary of a VIE is required to consolidate the VIE. The financial statements do not reflect any consolidation of VIEs.In 2022, WPL 2022 Solar Holdco, LLC was formed as a joint venture to own and operate project companies responsible for the construction, ownership and operation of various solar generation assets. Members of the joint venture were a WPL subsidiary (the managing member) and a tax equity partner. In the second quarter of 2022, the WPL subsidiary and the tax equity partner contributed $62 million and $29 million, respectively, to WPL 2022 Solar Holdco, LLC in exchange for membership interests, and $88 million of the contributed funds were paid to WPL in exchange for equity interests in the project companies. The tax equity partner's contributions were represented as a noncontrolling interest within total equity on Alliant Energy’s and WPL’s balance sheets as of June 30, 2022. In the second quarter of 2022, Alliant Energy and WPL consolidated this joint venture as it was a VIE in which WPL held a variable interest, and WPL controlled decisions that were significant to the joint venture’s ongoing operations and economic results (i.e., WPL was the primary beneficiary).In August 2022, the Inflation Reduction Act of 2022 was enacted. Following its enactment, WPL evaluated the provisions of the new legislation and determined that retaining full ownership of the solar projects is expected to result in more cost benefits for its customers. As a result, in the third quarter of 2022, WPL and the tax equity partner terminated the tax equity partnership, and WPL returned the $29 million of initial funding to the tax equity partner, resulting in the reversal of the noncontrolling interest within total equity on Alliant Energy’s and WPL’s balance sheets as of December 31, 2022. Alliant Energy and WPL no longer expect their solar generation project construction costs to be financed with capital from tax equity partners, which would result in higher rate base amounts compared to those previously approved by the PSCW for WPL’s planned approximately 1,100 MW of solar generation. Alliant Energy and WPL concluded that no disallowance of anticipated higher rate base amounts was required as of December 31, 2022 given full ownership of WPL's planned solar generation is expected to result in more cost benefits for WPL's customers.
Leases	The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease, if known, is used to determine the present value of the lease payments. If the rate implicit in the lease is not known, the incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and amortization, and interest expenses. Finance lease assets related to leased land for solar generation are amortized on a straight-line basis over the lease term, and are accounted for as operating leases for rate-making purposes. All other finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.
IPL [Member]
Property, Plant and Equipment [Line Items]
General, Basis of Presentation	The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method.All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes.
General, Basis of Accounting	The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction.
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.
General, Use of Estimates	The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Regulatory Assets and Regulatory Liabilities	Alliant Energy, IPL and WPL are subject to regulation by FERC and various state regulatory commissions. As a result, Alliant Energy, IPL and WPL are subject to GAAP provisions for regulated operations, which provide that rate-regulated public utilities record certain costs and credits allowed in the rate-making process in different periods than for non-utility entities. Regulatory assets generally represent incurred costs that have been deferred as such costs are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the related costs have not yet been incurred. Amounts recorded as regulatory assets or regulatory liabilities are generally recognized in the income statements at the time they are reflected in rates.
Income Taxes	The liability method of accounting is followed for deferred taxes, which requires the establishment of deferred tax assets and liabilities, as appropriate, for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state apportionment. Changes in deferred tax assets and liabilities associated with certain property-related differences at IPL are accounted for differently than other subsidiaries of Alliant Energy due to rate-making practices in Iowa. Rate-making practices in Iowa do not allow the impact of certain deferred tax expenses (benefits) to be included in the determination of retail rates. Based on these rate-making practices, deferred tax expense (benefit) related to these property-related differences at IPL is not recorded in the income statement but instead recorded to regulatory assets or regulatory liabilities until these temporary differences reverse. In Wisconsin, the PSCW allows rate recovery of deferred tax expense on all temporary differences. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Federal Tax Reform repealed corporate federal alternative minimum tax and allowed unutilized alternative minimum tax credits to be refunded over four tax years beginning with the U.S. federal tax return for calendar year 2018. Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, Alliant Energy received the remaining alternative minimum tax credits refunds in 2020. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the modified separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). The difference in the income taxes recorded for IPL and WPL under the modified separate return method compared to the income taxes recorded on a separate return basis was not material in 2022, 2021 and 2020.
Cash, Cash Equivalents and Restricted Cash	Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days. At December 31, 2022 and 2021, Alliant Energy’s restricted cash related to requirements in Sheboygan Power, LLC’s debt agreement.
Property, Plant and Equipment	Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements.
Depreciation	IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9%
AFUDC	AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3% In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs.
Revenue Recognition	Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the end of each customer’s last billing period. The unbilled component is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2022, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed.
Utility Cost Recovery Mechanisms	Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.
Financial Instruments	Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement.
Asset Impairments	Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value.
Asset Retirement Obligations	The fair value of a legal obligation associated with the retirement of an asset is recorded as a liability when an asset is placed in service, when a legal obligation is subsequently identified or when sufficient information becomes available to determine a reasonable estimate of the fair value of future retirement costs. When an ARO is recorded as a liability, an equivalent amount is added to the asset cost. The fair value of AROs at inception is determined using discounted cash flows analyses. The liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset. Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory assets on the balance sheets. Revisions in estimated cash flows for IPL’s and WPL’s regulated operations are recorded as an increase or decrease to the ARO liability, with an offset to the asset cost, unless the asset is already retired and then the offset is recorded to regulatory assets or regulatory liabilities on the balance sheets. Upon regulatory approval to recover IPL’s AROs expenditures, its regulatory assets are amortized to depreciation and amortization expenses in Alliant Energy’s and IPL’s income statements over the same time period the ARO expenditures are recovered from IPL’s customers. WPL’s regulatory assets related to AROs are recovered as a component of depreciation rates pursuant to PSCW and FERC orders. Upon settlement of the ARO liability, an entity settles the obligation for its recorded amount or incurs a gain or loss. Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the balance sheets.
Debt Issuance and Retirement Costs	Debt issuance costs and debt premiums or discounts are presented on the balance sheets as a direct adjustment to the carrying amount of the related debt liability, and are deferred and amortized over the expected life of each debt issue, considering maturity dates and, if applicable, redemption rights held by others. Alliant Energy’s non-utility businesses and Corporate Services record to interest expense in the period of retirement any unamortized debt issuance costs and debt premiums or discounts on debt retired early.
Current Expected Credit Losses Estimates	Current expected credit losses are estimated for trade and other receivables and credit exposures on guarantees of the performance by third parties. The current expected credit losses for short-term trade receivables are based on estimates of losses resulting from the inability of customers to make required payments. The methodology used to estimate losses is based on historical write-offs, regional economic conditions, significant events that could impact collectability, such as impacts related to COVID-19, significant weather related matters including the derecho windstorm and related regulatory actions, and forecasted changes to the accounts receivable aging portfolio and write-offs. The current expected credit losses related to guarantees of the performance by third parties are estimated using both quantitative and qualitative information, which utilizes potential outcomes in a range of possible estimated amounts. In 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables, certain other assets and off-balance sheet credit exposures. Alliant Energy, IPL and WPL adopted this standard on January 1, 2020 using a modified retrospective method of adoption, which required cumulative effect adjustments to retained earnings on January 1, 2020. IPL and WPL did not record a cumulative effect adjustment to retained earnings and Alliant Energy recorded a pre-tax $12 million (after-tax $9 million) cumulative effect adjustment to decrease retained earnings related to Alliant Energy’s guarantees in the partnership obligations of an affiliate of Whiting Petroleum (refer to Note 17(d) for further discussion). This adjustment is included in “Adoption of new accounting standard” in Alliant Energy’s equity statement for 2020.
Variable Interest Entities	An entity is considered a VIE if its equity investors do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties, the entity is structured with disproportionate voting rights and substantially all of the entity’s activities are conducted on behalf of the investor with disproportionately fewer voting rights, or its equity investors lack any of the following characteristics: (1) power, through voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb expected losses of the entity; or (3) the right to receive expected benefits of the entity. The primary beneficiary of a VIE is required to consolidate the VIE. The financial statements do not reflect any consolidation of VIEs.In 2022, WPL 2022 Solar Holdco, LLC was formed as a joint venture to own and operate project companies responsible for the construction, ownership and operation of various solar generation assets. Members of the joint venture were a WPL subsidiary (the managing member) and a tax equity partner. In the second quarter of 2022, the WPL subsidiary and the tax equity partner contributed $62 million and $29 million, respectively, to WPL 2022 Solar Holdco, LLC in exchange for membership interests, and $88 million of the contributed funds were paid to WPL in exchange for equity interests in the project companies. The tax equity partner's contributions were represented as a noncontrolling interest within total equity on Alliant Energy’s and WPL’s balance sheets as of June 30, 2022. In the second quarter of 2022, Alliant Energy and WPL consolidated this joint venture as it was a VIE in which WPL held a variable interest, and WPL controlled decisions that were significant to the joint venture’s ongoing operations and economic results (i.e., WPL was the primary beneficiary).In August 2022, the Inflation Reduction Act of 2022 was enacted. Following its enactment, WPL evaluated the provisions of the new legislation and determined that retaining full ownership of the solar projects is expected to result in more cost benefits for its customers. As a result, in the third quarter of 2022, WPL and the tax equity partner terminated the tax equity partnership, and WPL returned the $29 million of initial funding to the tax equity partner, resulting in the reversal of the noncontrolling interest within total equity on Alliant Energy’s and WPL’s balance sheets as of December 31, 2022. Alliant Energy and WPL no longer expect their solar generation project construction costs to be financed with capital from tax equity partners, which would result in higher rate base amounts compared to those previously approved by the PSCW for WPL’s planned approximately 1,100 MW of solar generation. Alliant Energy and WPL concluded that no disallowance of anticipated higher rate base amounts was required as of December 31, 2022 given full ownership of WPL's planned solar generation is expected to result in more cost benefits for WPL's customers.
Leases	The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease, if known, is used to determine the present value of the lease payments. If the rate implicit in the lease is not known, the incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and amortization, and interest expenses. Finance lease assets related to leased land for solar generation are amortized on a straight-line basis over the lease term, and are accounted for as operating leases for rate-making purposes. All other finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.
WPL [Member]
Property, Plant and Equipment [Line Items]
General, Basis of Presentation	The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method.All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes.
General, Basis of Accounting	The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction.
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.
General, Use of Estimates	The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Regulatory Assets and Regulatory Liabilities	Alliant Energy, IPL and WPL are subject to regulation by FERC and various state regulatory commissions. As a result, Alliant Energy, IPL and WPL are subject to GAAP provisions for regulated operations, which provide that rate-regulated public utilities record certain costs and credits allowed in the rate-making process in different periods than for non-utility entities. Regulatory assets generally represent incurred costs that have been deferred as such costs are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the related costs have not yet been incurred. Amounts recorded as regulatory assets or regulatory liabilities are generally recognized in the income statements at the time they are reflected in rates.
Income Taxes	The liability method of accounting is followed for deferred taxes, which requires the establishment of deferred tax assets and liabilities, as appropriate, for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state apportionment. Changes in deferred tax assets and liabilities associated with certain property-related differences at IPL are accounted for differently than other subsidiaries of Alliant Energy due to rate-making practices in Iowa. Rate-making practices in Iowa do not allow the impact of certain deferred tax expenses (benefits) to be included in the determination of retail rates. Based on these rate-making practices, deferred tax expense (benefit) related to these property-related differences at IPL is not recorded in the income statement but instead recorded to regulatory assets or regulatory liabilities until these temporary differences reverse. In Wisconsin, the PSCW allows rate recovery of deferred tax expense on all temporary differences. The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation. Federal Tax Reform repealed corporate federal alternative minimum tax and allowed unutilized alternative minimum tax credits to be refunded over four tax years beginning with the U.S. federal tax return for calendar year 2018. Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, Alliant Energy received the remaining alternative minimum tax credits refunds in 2020. Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the modified separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis). The difference in the income taxes recorded for IPL and WPL under the modified separate return method compared to the income taxes recorded on a separate return basis was not material in 2022, 2021 and 2020.
Cash, Cash Equivalents and Restricted Cash	Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days. At December 31, 2022 and 2021, Alliant Energy’s restricted cash related to requirements in Sheboygan Power, LLC’s debt agreement.
Property, Plant and Equipment	Utility Plant - General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement. Non-utility and Other Property - General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements. Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements.
Depreciation	IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023.
AFUDC	AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3% In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs.
Revenue Recognition	Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is estimated and recorded at the end of each reporting period based on estimated amounts of energy delivered to customers since the end of each customer’s last billing period. The unbilled component is based on estimates of daily system demand volumes, customer usage by class, temperature impacts, line losses and the most recent customer rates. IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2022, the related amounts accrued for IPL and WPL were not material. IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements. Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers. Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues. Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed.
Utility Cost Recovery Mechanisms	Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements. IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers. IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism. Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements. IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers. WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers. IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation. Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.
Financial Instruments	Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement.
Asset Impairments	Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized. Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value.
Asset Retirement Obligations	The fair value of a legal obligation associated with the retirement of an asset is recorded as a liability when an asset is placed in service, when a legal obligation is subsequently identified or when sufficient information becomes available to determine a reasonable estimate of the fair value of future retirement costs. When an ARO is recorded as a liability, an equivalent amount is added to the asset cost. The fair value of AROs at inception is determined using discounted cash flows analyses. The liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset. Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory assets on the balance sheets. Revisions in estimated cash flows for IPL’s and WPL’s regulated operations are recorded as an increase or decrease to the ARO liability, with an offset to the asset cost, unless the asset is already retired and then the offset is recorded to regulatory assets or regulatory liabilities on the balance sheets. Upon regulatory approval to recover IPL’s AROs expenditures, its regulatory assets are amortized to depreciation and amortization expenses in Alliant Energy’s and IPL’s income statements over the same time period the ARO expenditures are recovered from IPL’s customers. WPL’s regulatory assets related to AROs are recovered as a component of depreciation rates pursuant to PSCW and FERC orders. Upon settlement of the ARO liability, an entity settles the obligation for its recorded amount or incurs a gain or loss. Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the balance sheets.
Debt Issuance and Retirement Costs	Debt issuance costs and debt premiums or discounts are presented on the balance sheets as a direct adjustment to the carrying amount of the related debt liability, and are deferred and amortized over the expected life of each debt issue, considering maturity dates and, if applicable, redemption rights held by others. Alliant Energy’s non-utility businesses and Corporate Services record to interest expense in the period of retirement any unamortized debt issuance costs and debt premiums or discounts on debt retired early.
Current Expected Credit Losses Estimates	Current expected credit losses are estimated for trade and other receivables and credit exposures on guarantees of the performance by third parties. The current expected credit losses for short-term trade receivables are based on estimates of losses resulting from the inability of customers to make required payments. The methodology used to estimate losses is based on historical write-offs, regional economic conditions, significant events that could impact collectability, such as impacts related to COVID-19, significant weather related matters including the derecho windstorm and related regulatory actions, and forecasted changes to the accounts receivable aging portfolio and write-offs. The current expected credit losses related to guarantees of the performance by third parties are estimated using both quantitative and qualitative information, which utilizes potential outcomes in a range of possible estimated amounts. In 2016, the Financial Accounting Standards Board issued an accounting standard requiring use of a current expected credit loss model rather than an incurred loss method, which is intended to result in more timely recognition of credit losses on trade receivables, certain other assets and off-balance sheet credit exposures. Alliant Energy, IPL and WPL adopted this standard on January 1, 2020 using a modified retrospective method of adoption, which required cumulative effect adjustments to retained earnings on January 1, 2020. IPL and WPL did not record a cumulative effect adjustment to retained earnings and Alliant Energy recorded a pre-tax $12 million (after-tax $9 million) cumulative effect adjustment to decrease retained earnings related to Alliant Energy’s guarantees in the partnership obligations of an affiliate of Whiting Petroleum (refer to Note 17(d) for further discussion). This adjustment is included in “Adoption of new accounting standard” in Alliant Energy’s equity statement for 2020.
Variable Interest Entities	An entity is considered a VIE if its equity investors do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties, the entity is structured with disproportionate voting rights and substantially all of the entity’s activities are conducted on behalf of the investor with disproportionately fewer voting rights, or its equity investors lack any of the following characteristics: (1) power, through voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb expected losses of the entity; or (3) the right to receive expected benefits of the entity. The primary beneficiary of a VIE is required to consolidate the VIE. The financial statements do not reflect any consolidation of VIEs.In 2022, WPL 2022 Solar Holdco, LLC was formed as a joint venture to own and operate project companies responsible for the construction, ownership and operation of various solar generation assets. Members of the joint venture were a WPL subsidiary (the managing member) and a tax equity partner. In the second quarter of 2022, the WPL subsidiary and the tax equity partner contributed $62 million and $29 million, respectively, to WPL 2022 Solar Holdco, LLC in exchange for membership interests, and $88 million of the contributed funds were paid to WPL in exchange for equity interests in the project companies. The tax equity partner's contributions were represented as a noncontrolling interest within total equity on Alliant Energy’s and WPL’s balance sheets as of June 30, 2022. In the second quarter of 2022, Alliant Energy and WPL consolidated this joint venture as it was a VIE in which WPL held a variable interest, and WPL controlled decisions that were significant to the joint venture’s ongoing operations and economic results (i.e., WPL was the primary beneficiary).In August 2022, the Inflation Reduction Act of 2022 was enacted. Following its enactment, WPL evaluated the provisions of the new legislation and determined that retaining full ownership of the solar projects is expected to result in more cost benefits for its customers. As a result, in the third quarter of 2022, WPL and the tax equity partner terminated the tax equity partnership, and WPL returned the $29 million of initial funding to the tax equity partner, resulting in the reversal of the noncontrolling interest within total equity on Alliant Energy’s and WPL’s balance sheets as of December 31, 2022. Alliant Energy and WPL no longer expect their solar generation project construction costs to be financed with capital from tax equity partners, which would result in higher rate base amounts compared to those previously approved by the PSCW for WPL’s planned approximately 1,100 MW of solar generation. Alliant Energy and WPL concluded that no disallowance of anticipated higher rate base amounts was required as of December 31, 2022 given full ownership of WPL's planned solar generation is expected to result in more cost benefits for WPL's customers.
Leases	The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease, if known, is used to determine the present value of the lease payments. If the rate implicit in the lease is not known, the incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and amortization, and interest expenses. Finance lease assets related to leased land for solar generation are amortized on a straight-line basis over the lease term, and are accounted for as operating leases for rate-making purposes. All other finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

Summary Of Significant Accoun_3

Summary Of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of Average Rates of Depreciation	The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023.
Schedule of Allowance for Funds Used During Construction Rate	The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3%
IPL [Member]
Schedule of Average Rates of Depreciation	The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9% In December 2021, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2023 as a result of a recently completed depreciation study. WPL estimates the new average rates of depreciation for its electric generation, electric distribution and gas properties will be approximately 3.6%, 2.7% and 2.9%, respectively, during 2023.
Schedule of Allowance for Funds Used During Construction Rate	The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3%
WPL [Member]
Schedule of Average Rates of Depreciation	The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows: IPL WPL 2022 2021 2020 2022 2021 2020 Electric - generation 3.4% 3.4% 3.5% 3.4% 3.5% 3.5% Electric - distribution 2.8% 2.9% 2.8% 2.5% 2.6% 2.6% Electric - other 5.7% 5.7% 5.2% 6.8% 7.4% 6.1% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.4% Other 6.1% 6.1% 6.3% 4.9% 5.4% 5.9%
Schedule of Allowance for Funds Used During Construction Rate	The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2022 2021 2020 IPL (Wind generation CWIP) 6.9% 7.0% 7.1% IPL (other CWIP) 7.0% 7.2% 7.2% WPL (retail jurisdiction) 7.0% 7.0% 7.0% WPL (wholesale jurisdiction) 6.2% 5.6% 6.3%

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2022
Regulatory Assets [Line Items]
Schedule of Regulatory Assets	At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $929 $934 $848 $884 $81 $50 Pension and OPEB costs 392 462 197 228 195 234 Commodity cost recovery 160 42 1 2 159 40 AROs 151 128 110 89 41 39 Derivatives 84 8 48 4 36 4 Assets retired early 70 92 53 66 17 26 IPL’s DAEC PPA amendment 66 90 66 90 — — WPL’s Western Wisconsin gas distribution expansion investments 48 52 — — 48 52 Other 146 132 63 80 83 52 $2,046 $1,940 $1,386 $1,443 $660 $497
Assets Retired Early	Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2022 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $16 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 13 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 24 Return of remaining net book value through 2028 IUB and FERC WPL Edgewater Unit 4 2018 17 Return of and return on remaining net book value through 2028 PSCW and FERC
Schedule of Regulatory Liabilities	At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $579 $585 $303 $312 $276 $273 Cost of removal obligations 398 384 259 252 139 132 Derivatives 210 166 115 77 95 89 Commodity cost recovery 40 17 38 15 2 2 WPL’s West Riverside liquidated damages 32 36 — — 32 36 Electric transmission cost recovery 20 51 10 27 10 24 Other 45 32 29 8 16 24 $1,324 $1,271 $754 $691 $570 $580
IPL [Member]
Regulatory Assets [Line Items]
Schedule of Regulatory Assets	At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $929 $934 $848 $884 $81 $50 Pension and OPEB costs 392 462 197 228 195 234 Commodity cost recovery 160 42 1 2 159 40 AROs 151 128 110 89 41 39 Derivatives 84 8 48 4 36 4 Assets retired early 70 92 53 66 17 26 IPL’s DAEC PPA amendment 66 90 66 90 — — WPL’s Western Wisconsin gas distribution expansion investments 48 52 — — 48 52 Other 146 132 63 80 83 52 $2,046 $1,940 $1,386 $1,443 $660 $497
Assets Retired Early	Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2022 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $16 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 13 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 24 Return of remaining net book value through 2028 IUB and FERC WPL Edgewater Unit 4 2018 17 Return of and return on remaining net book value through 2028 PSCW and FERC
Schedule of Regulatory Liabilities	At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $579 $585 $303 $312 $276 $273 Cost of removal obligations 398 384 259 252 139 132 Derivatives 210 166 115 77 95 89 Commodity cost recovery 40 17 38 15 2 2 WPL’s West Riverside liquidated damages 32 36 — — 32 36 Electric transmission cost recovery 20 51 10 27 10 24 Other 45 32 29 8 16 24 $1,324 $1,271 $754 $691 $570 $580
WPL [Member]
Regulatory Assets [Line Items]
Schedule of Regulatory Assets	At December 31, regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $929 $934 $848 $884 $81 $50 Pension and OPEB costs 392 462 197 228 195 234 Commodity cost recovery 160 42 1 2 159 40 AROs 151 128 110 89 41 39 Derivatives 84 8 48 4 36 4 Assets retired early 70 92 53 66 17 26 IPL’s DAEC PPA amendment 66 90 66 90 — — WPL’s Western Wisconsin gas distribution expansion investments 48 52 — — 48 52 Other 146 132 63 80 83 52 $2,046 $1,940 $1,386 $1,443 $660 $497
Assets Retired Early	Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions): Entity Asset Retirement Date Regulatory Asset Balance as of Dec. 31, 2022 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $16 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 13 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 24 Return of remaining net book value through 2028 IUB and FERC WPL Edgewater Unit 4 2018 17 Return of and return on remaining net book value through 2028 PSCW and FERC
Schedule of Regulatory Liabilities	At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Tax-related $579 $585 $303 $312 $276 $273 Cost of removal obligations 398 384 259 252 139 132 Derivatives 210 166 115 77 95 89 Commodity cost recovery 40 17 38 15 2 2 WPL’s West Riverside liquidated damages 32 36 — — 32 36 Electric transmission cost recovery 20 51 10 27 10 24 Other 45 32 29 8 16 24 $1,324 $1,271 $754 $691 $570 $580

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Utility: Electric plant: Generation in service $8,060 $7,539 $4,962 $4,922 $3,098 $2,617 Distribution in service 6,912 6,537 3,876 3,652 3,036 2,885 Other in service 543 540 354 363 189 177 Anticipated to be retired early (a) 2,103 2,094 491 487 1,612 1,607 Total electric plant 17,618 16,710 9,683 9,424 7,935 7,286 Gas plant in service 1,705 1,636 910 878 795 758 Other plant in service 624 621 402 398 222 223 Accumulated depreciation (5,690) (5,263) (3,149) (2,897) (2,541) (2,366) Net plant 14,257 13,704 7,846 7,803 6,411 5,901 Leased Sheboygan Falls Energy Facility, net (b) — — — — 15 21 Leased land for solar generation, net 133 11 — — 133 11 Construction work in progress 1,357 778 194 174 1,163 604 Other, net 6 7 6 6 — 1 Total utility 15,753 14,500 8,046 7,983 7,722 6,538 Non-utility and other: Non-utility Generation, net (c) 71 75 — — — — Corporate Services and other, net (d) 423 412 — — — — Total non-utility and other 494 487 — — — — Total property, plant and equipment $16,247 $14,987 $8,046 $7,983 $7,722 $6,538 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing in the first half of 2023 and Edgewater Unit 5 by June 1, 2025. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and IPL concluded that Lansing, and Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2, met the criteria to be considered probable of abandonment as of December 31, 2022. IPL and WPL are currently allowed a full recovery of and a full return on its respective EGUs from both its retail and wholesale customers, and as a result, Alliant Energy, IPL and WPL concluded that no disallowance was required as of December 31, 2022. As of December 31, 2022, net book values were $233 million for Lansing, $511 million for Edgewater Unit 5, and $440 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $106 million and $100 million for WPL as of December 31, 2022 and 2021, respectively. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (c) Less accumulated depreciation of $71 million and $67 million for Alliant Energy as of December 31, 2022 and 2021, respectively. (d) Less accumulated depreciation of $269 million and $245 million for Alliant Energy as of December 31, 2022 and 2021, respectively.
Allowance For Funds Used During Construction	The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Equity $44 $18 $39 $8 $7 $17 $36 $11 $22 Debt 16 7 16 3 2 7 13 5 9 $60 $25 $55 $11 $9 $24 $49 $16 $31
IPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Utility: Electric plant: Generation in service $8,060 $7,539 $4,962 $4,922 $3,098 $2,617 Distribution in service 6,912 6,537 3,876 3,652 3,036 2,885 Other in service 543 540 354 363 189 177 Anticipated to be retired early (a) 2,103 2,094 491 487 1,612 1,607 Total electric plant 17,618 16,710 9,683 9,424 7,935 7,286 Gas plant in service 1,705 1,636 910 878 795 758 Other plant in service 624 621 402 398 222 223 Accumulated depreciation (5,690) (5,263) (3,149) (2,897) (2,541) (2,366) Net plant 14,257 13,704 7,846 7,803 6,411 5,901 Leased Sheboygan Falls Energy Facility, net (b) — — — — 15 21 Leased land for solar generation, net 133 11 — — 133 11 Construction work in progress 1,357 778 194 174 1,163 604 Other, net 6 7 6 6 — 1 Total utility 15,753 14,500 8,046 7,983 7,722 6,538 Non-utility and other: Non-utility Generation, net (c) 71 75 — — — — Corporate Services and other, net (d) 423 412 — — — — Total non-utility and other 494 487 — — — — Total property, plant and equipment $16,247 $14,987 $8,046 $7,983 $7,722 $6,538 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing in the first half of 2023 and Edgewater Unit 5 by June 1, 2025. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and IPL concluded that Lansing, and Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2, met the criteria to be considered probable of abandonment as of December 31, 2022. IPL and WPL are currently allowed a full recovery of and a full return on its respective EGUs from both its retail and wholesale customers, and as a result, Alliant Energy, IPL and WPL concluded that no disallowance was required as of December 31, 2022. As of December 31, 2022, net book values were $233 million for Lansing, $511 million for Edgewater Unit 5, and $440 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $106 million and $100 million for WPL as of December 31, 2022 and 2021, respectively. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (c) Less accumulated depreciation of $71 million and $67 million for Alliant Energy as of December 31, 2022 and 2021, respectively. (d) Less accumulated depreciation of $269 million and $245 million for Alliant Energy as of December 31, 2022 and 2021, respectively.
Allowance For Funds Used During Construction	The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Equity $44 $18 $39 $8 $7 $17 $36 $11 $22 Debt 16 7 16 3 2 7 13 5 9 $60 $25 $55 $11 $9 $24 $49 $16 $31
WPL [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Utility: Electric plant: Generation in service $8,060 $7,539 $4,962 $4,922 $3,098 $2,617 Distribution in service 6,912 6,537 3,876 3,652 3,036 2,885 Other in service 543 540 354 363 189 177 Anticipated to be retired early (a) 2,103 2,094 491 487 1,612 1,607 Total electric plant 17,618 16,710 9,683 9,424 7,935 7,286 Gas plant in service 1,705 1,636 910 878 795 758 Other plant in service 624 621 402 398 222 223 Accumulated depreciation (5,690) (5,263) (3,149) (2,897) (2,541) (2,366) Net plant 14,257 13,704 7,846 7,803 6,411 5,901 Leased Sheboygan Falls Energy Facility, net (b) — — — — 15 21 Leased land for solar generation, net 133 11 — — 133 11 Construction work in progress 1,357 778 194 174 1,163 604 Other, net 6 7 6 6 — 1 Total utility 15,753 14,500 8,046 7,983 7,722 6,538 Non-utility and other: Non-utility Generation, net (c) 71 75 — — — — Corporate Services and other, net (d) 423 412 — — — — Total non-utility and other 494 487 — — — — Total property, plant and equipment $16,247 $14,987 $8,046 $7,983 $7,722 $6,538 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing in the first half of 2023 and Edgewater Unit 5 by June 1, 2025. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and IPL concluded that Lansing, and Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2, met the criteria to be considered probable of abandonment as of December 31, 2022. IPL and WPL are currently allowed a full recovery of and a full return on its respective EGUs from both its retail and wholesale customers, and as a result, Alliant Energy, IPL and WPL concluded that no disallowance was required as of December 31, 2022. As of December 31, 2022, net book values were $233 million for Lansing, $511 million for Edgewater Unit 5, and $440 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $106 million and $100 million for WPL as of December 31, 2022 and 2021, respectively. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment. (c) Less accumulated depreciation of $71 million and $67 million for Alliant Energy as of December 31, 2022 and 2021, respectively. (d) Less accumulated depreciation of $269 million and $245 million for Alliant Energy as of December 31, 2022 and 2021, respectively.
Allowance For Funds Used During Construction	The amount of AFUDC generated by equity and debt components was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Equity $44 $18 $39 $8 $7 $17 $36 $11 $22 Debt 16 7 16 3 2 7 13 5 9 $60 $25 $55 $11 $9 $24 $49 $16 $31

Jointly-Owned Electric Utilit_2

Jointly-Owned Electric Utility Plant (Tables)	12 Months Ended
	Dec. 31, 2022
Jointly Owned Electric Utility Plant [Line Items]
Components of Jointly-Owned Electric Utility Plants	Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2022 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $612 $241 $17 George Neal Unit 4 25.7% 193 103 4 George Neal Unit 3 28.0% 176 80 6 Louisa Unit 1 4.0% 43 21 — 1,024 445 27 WPL Columbia Units 1-2 53.5% 805 338 13 West Riverside Energy Center and Solar Facility 91.0% 716 53 2 Forward Wind Energy Center 42.6% 118 50 — 1,639 441 15 Alliant Energy $2,663 $886 $42
IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Components of Jointly-Owned Electric Utility Plants	Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2022 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $612 $241 $17 George Neal Unit 4 25.7% 193 103 4 George Neal Unit 3 28.0% 176 80 6 Louisa Unit 1 4.0% 43 21 — 1,024 445 27 WPL Columbia Units 1-2 53.5% 805 338 13 West Riverside Energy Center and Solar Facility 91.0% 716 53 2 Forward Wind Energy Center 42.6% 118 50 — 1,639 441 15 Alliant Energy $2,663 $886 $42
WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Components of Jointly-Owned Electric Utility Plants	Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2022 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $612 $241 $17 George Neal Unit 4 25.7% 193 103 4 George Neal Unit 3 28.0% 176 80 6 Louisa Unit 1 4.0% 43 21 — 1,024 445 27 WPL Columbia Units 1-2 53.5% 805 338 13 West Riverside Energy Center and Solar Facility 91.0% 716 53 2 Forward Wind Energy Center 42.6% 118 50 — 1,639 441 15 Alliant Energy $2,663 $886 $42

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2022
Accounts Receivable [Line Items]
Accounts Receivable Details	Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Customer $114 $93 $— $— $102 $82 Unbilled utility revenues 115 91 — — 115 91 Deferred proceeds 185 214 185 214 — — Other 109 53 74 28 34 25 Allowance for expected credit losses (7) (11) — (1) (7) (10) $516 $440 $259 $241 $244 $188
Maximum And Average Outstanding Cash Proceeds	IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program were as follows (in millions): Maximum Average 2022 2021 2020 2022 2021 2020 Outstanding aggregate cash proceeds $80 $110 $96 $14 $46 $9
Receivables Sold Under the Agreement	As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 Customer accounts receivable $145 $125 Unbilled utility revenues 132 104 Receivables sold to third party 277 229 Less: cash proceeds 80 1 Deferred proceeds 197 228 Less: allowance for expected credit losses 12 14 Fair value of deferred proceeds $185 $214 Outstanding receivables past due $26 $22
Additional Attributes Of Receivables Sold Under The Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 2020 Collections $2,302 $2,134 $2,025 Write-offs, net of recoveries 9 9 7
IPL [Member]
Accounts Receivable [Line Items]
Accounts Receivable Details	Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Customer $114 $93 $— $— $102 $82 Unbilled utility revenues 115 91 — — 115 91 Deferred proceeds 185 214 185 214 — — Other 109 53 74 28 34 25 Allowance for expected credit losses (7) (11) — (1) (7) (10) $516 $440 $259 $241 $244 $188
Maximum And Average Outstanding Cash Proceeds	IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program were as follows (in millions): Maximum Average 2022 2021 2020 2022 2021 2020 Outstanding aggregate cash proceeds $80 $110 $96 $14 $46 $9
Receivables Sold Under the Agreement	As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 Customer accounts receivable $145 $125 Unbilled utility revenues 132 104 Receivables sold to third party 277 229 Less: cash proceeds 80 1 Deferred proceeds 197 228 Less: allowance for expected credit losses 12 14 Fair value of deferred proceeds $185 $214 Outstanding receivables past due $26 $22
Additional Attributes Of Receivables Sold Under The Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2022 2021 2020 Collections $2,302 $2,134 $2,025 Write-offs, net of recoveries 9 9 7
WPL [Member]
Accounts Receivable [Line Items]
Accounts Receivable Details	Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Customer $114 $93 $— $— $102 $82 Unbilled utility revenues 115 91 — — 115 91 Deferred proceeds 185 214 185 214 — — Other 109 53 74 28 34 25 Allowance for expected credit losses (7) (11) — (1) (7) (10) $516 $440 $259 $241 $244 $188

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Unconsolidated Equity Investments	Alliant Energy’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions): Ownership Interest at Carrying Value at December 31, Equity (Income) / Loss December 31, 2022 2022 2021 2022 2021 2020 ATC Holdings 16%, 20% $358 $338 ($41) ($43) ($47) Non-utility wind farm in Oklahoma 50% 101 99 (5) (4) (8) Corporate venture investments Various 62 52 (3) (13) (4) Other Various 21 19 (2) (2) (2) $542 $508 ($51) ($62) ($61)
Summary Financial Information	Summary aggregate financial information from the financial statements of these holdings is as follows (in millions): Alliant Energy 2022 2021 2020 Revenues $813 $802 $801 Operating income 350 357 376 Net income 675 358 343 As of December 31: Current assets 227 112 Non-current assets 8,292 7,036 Current liabilities 620 455 Non-current liabilities 3,285 3,110 Noncontrolling interest 289 247

Common Equity (Tables)

Common Equity (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of Common Equity [Line Items]
Common Stock Activity	A summary of Alliant Energy’s common stock activity was as follows: 2022 2021 2020 Shares outstanding, January 1 250,474,529 249,868,415 245,022,800 Equity forward agreements — — 4,275,127 Shareowner Direct Plan 437,669 492,565 472,283 Equity-based compensation plans 222,768 113,549 98,205 Shares outstanding, December 31 251,134,966 250,474,529 249,868,415

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2022
Debt Instrument [Line Items]
Schedule of 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): Alliant Energy IPL WPL December 31 2022 2021 2022 2021 2022 2021 Amount outstanding $642 $515 $— $— $290 $236 Weighted average interest rates 4.6% 0.2% N/A N/A 4.5% 0.2% Available credit facility capacity $358 $485 $100 $250 $110 $64 Alliant Energy IPL WPL For the year ended 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $665 $648 $— $19 $325 $320 Average amount outstanding (based on daily outstanding balances) $411 $459 $— $— $153 $172 Weighted average interest rates 2.1% 0.2% —% 0.2% 1.6% 0.1%
Schedule of Long-term Debt	Long-term debt, net as of December 31 was as follows (dollars in millions): 2022 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 3.25%, due 2024 $500 $500 $— $500 $500 $— 3.4%, due 2025 250 250 — 250 250 — 5.5%, due 2025 50 50 — 50 50 — 4.1%, due 2028 500 500 — 500 500 — 3.6%, due 2029 300 300 — 300 300 — 2.3%, due 2030 400 400 — 400 400 — 6.45%, due 2033 100 100 — 100 100 — 6.3%, due 2034 125 125 — 125 125 — 6.25%, due 2039 300 300 — 300 300 — 4.7%, due 2043 250 250 — 250 250 — 3.7%, due 2046 300 300 — 300 300 — 3.5%, due 2049 300 300 — 300 300 — 3.1%, due 2051 300 300 — 300 300 — 3,675 3,675 — 3,675 3,675 — Debentures (a): 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 300 — 300 300 — 300 3.95%, due 2032 (b) 600 — 600 — — — 6.25%, due 2034 100 — 100 100 — 100 6.375%, due 2037 300 — 300 300 — 300 7.6%, due 2038 250 — 250 250 — 250 4.1%, due 2044 250 — 250 250 — 250 3.65%, due 2050 350 — 350 350 — 350 2.25% (Retired in 2022) — — — 250 — 250 2,800 — 2,800 2,450 — 2,450 Other: AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 400 — — AEF term loan credit agreement through March 2024, 5% at December 31, 2022 (with Alliant Energy as guarantor) (c) 400 — — — — — AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)(d) 350 — — — — — Sheboygan Power, LLC 5.06% senior secured notes, due 2023 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 17 — — 24 — — AEF term loan credit agreement, 1% at December 31, 2021 (with Alliant Energy as guarantor) (Retired in 2022) — — — 300 — — Corporate Services 3.45% senior notes (Retired in 2022) — — — 75 — — Other, 1% at December 31, 2022, due 2023 to 2025 1 — — 1 — — 1,668 — — 1,300 — — Subtotal 8,143 3,675 2,800 7,425 3,675 2,450 Current maturities (408) — — (633) — (250) Unamortized debt issuance costs (45) (21) (19) (42) (23) (15) Unamortized debt (discount) and premium, net (22) (8) (11) (15) (9) (6) Long-term debt, net (e) $7,668 $3,646 $2,770 $6,735 $3,643 $2,179 (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In August 2022, WPL issued $600 million of 3.95% debentures due 2032. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of WPL’s solar EGUs. (c) In March 2022, AEF entered into a $300 million variable rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022. In December 2022, AEF increased the amount outstanding under the new term loan credit agreement by $100 million and used the additional borrowings to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026. Under the terms of the swap, AEF exchanged variable rate borrowings for a fixed rate of 3.93%. (d) In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. (e) There were no significant sinking fund requirements related to the outstanding long-term debt.
Schedule of Maturities of Long-term Debt	At December 31, 2022, long-term debt maturities for 2023 through 2027 were as follows (in millions): 2023 2024 2025 2026 2027 IPL $— $500 $300 $— $— WPL — — — — 300 AEF 408 409 — 200 — Alliant Energy $408 $909 $300 $200 $300
IPL [Member]
Debt Instrument [Line Items]
Schedule of 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): Alliant Energy IPL WPL December 31 2022 2021 2022 2021 2022 2021 Amount outstanding $642 $515 $— $— $290 $236 Weighted average interest rates 4.6% 0.2% N/A N/A 4.5% 0.2% Available credit facility capacity $358 $485 $100 $250 $110 $64 Alliant Energy IPL WPL For the year ended 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $665 $648 $— $19 $325 $320 Average amount outstanding (based on daily outstanding balances) $411 $459 $— $— $153 $172 Weighted average interest rates 2.1% 0.2% —% 0.2% 1.6% 0.1%
Schedule of Long-term Debt	Long-term debt, net as of December 31 was as follows (dollars in millions): 2022 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 3.25%, due 2024 $500 $500 $— $500 $500 $— 3.4%, due 2025 250 250 — 250 250 — 5.5%, due 2025 50 50 — 50 50 — 4.1%, due 2028 500 500 — 500 500 — 3.6%, due 2029 300 300 — 300 300 — 2.3%, due 2030 400 400 — 400 400 — 6.45%, due 2033 100 100 — 100 100 — 6.3%, due 2034 125 125 — 125 125 — 6.25%, due 2039 300 300 — 300 300 — 4.7%, due 2043 250 250 — 250 250 — 3.7%, due 2046 300 300 — 300 300 — 3.5%, due 2049 300 300 — 300 300 — 3.1%, due 2051 300 300 — 300 300 — 3,675 3,675 — 3,675 3,675 — Debentures (a): 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 300 — 300 300 — 300 3.95%, due 2032 (b) 600 — 600 — — — 6.25%, due 2034 100 — 100 100 — 100 6.375%, due 2037 300 — 300 300 — 300 7.6%, due 2038 250 — 250 250 — 250 4.1%, due 2044 250 — 250 250 — 250 3.65%, due 2050 350 — 350 350 — 350 2.25% (Retired in 2022) — — — 250 — 250 2,800 — 2,800 2,450 — 2,450 Other: AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 400 — — AEF term loan credit agreement through March 2024, 5% at December 31, 2022 (with Alliant Energy as guarantor) (c) 400 — — — — — AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)(d) 350 — — — — — Sheboygan Power, LLC 5.06% senior secured notes, due 2023 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 17 — — 24 — — AEF term loan credit agreement, 1% at December 31, 2021 (with Alliant Energy as guarantor) (Retired in 2022) — — — 300 — — Corporate Services 3.45% senior notes (Retired in 2022) — — — 75 — — Other, 1% at December 31, 2022, due 2023 to 2025 1 — — 1 — — 1,668 — — 1,300 — — Subtotal 8,143 3,675 2,800 7,425 3,675 2,450 Current maturities (408) — — (633) — (250) Unamortized debt issuance costs (45) (21) (19) (42) (23) (15) Unamortized debt (discount) and premium, net (22) (8) (11) (15) (9) (6) Long-term debt, net (e) $7,668 $3,646 $2,770 $6,735 $3,643 $2,179 (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In August 2022, WPL issued $600 million of 3.95% debentures due 2032. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of WPL’s solar EGUs. (c) In March 2022, AEF entered into a $300 million variable rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022. In December 2022, AEF increased the amount outstanding under the new term loan credit agreement by $100 million and used the additional borrowings to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026. Under the terms of the swap, AEF exchanged variable rate borrowings for a fixed rate of 3.93%. (d) In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. (e) There were no significant sinking fund requirements related to the outstanding long-term debt.
Schedule of Maturities of Long-term Debt	At December 31, 2022, long-term debt maturities for 2023 through 2027 were as follows (in millions): 2023 2024 2025 2026 2027 IPL $— $500 $300 $— $— WPL — — — — 300 AEF 408 409 — 200 — Alliant Energy $408 $909 $300 $200 $300
WPL [Member]
Debt Instrument [Line Items]
Schedule of 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): Alliant Energy IPL WPL December 31 2022 2021 2022 2021 2022 2021 Amount outstanding $642 $515 $— $— $290 $236 Weighted average interest rates 4.6% 0.2% N/A N/A 4.5% 0.2% Available credit facility capacity $358 $485 $100 $250 $110 $64 Alliant Energy IPL WPL For the year ended 2022 2021 2022 2021 2022 2021 Maximum amount outstanding (based on daily outstanding balances) $665 $648 $— $19 $325 $320 Average amount outstanding (based on daily outstanding balances) $411 $459 $— $— $153 $172 Weighted average interest rates 2.1% 0.2% —% 0.2% 1.6% 0.1%
Schedule of Long-term Debt	Long-term debt, net as of December 31 was as follows (dollars in millions): 2022 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Senior Debentures (a): 3.25%, due 2024 $500 $500 $— $500 $500 $— 3.4%, due 2025 250 250 — 250 250 — 5.5%, due 2025 50 50 — 50 50 — 4.1%, due 2028 500 500 — 500 500 — 3.6%, due 2029 300 300 — 300 300 — 2.3%, due 2030 400 400 — 400 400 — 6.45%, due 2033 100 100 — 100 100 — 6.3%, due 2034 125 125 — 125 125 — 6.25%, due 2039 300 300 — 300 300 — 4.7%, due 2043 250 250 — 250 250 — 3.7%, due 2046 300 300 — 300 300 — 3.5%, due 2049 300 300 — 300 300 — 3.1%, due 2051 300 300 — 300 300 — 3,675 3,675 — 3,675 3,675 — Debentures (a): 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 300 — 300 300 — 300 3.95%, due 2032 (b) 600 — 600 — — — 6.25%, due 2034 100 — 100 100 — 100 6.375%, due 2037 300 — 300 300 — 300 7.6%, due 2038 250 — 250 250 — 250 4.1%, due 2044 250 — 250 250 — 250 3.65%, due 2050 350 — 350 350 — 350 2.25% (Retired in 2022) — — — 250 — 250 2,800 — 2,800 2,450 — 2,450 Other: AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 400 — — AEF term loan credit agreement through March 2024, 5% at December 31, 2022 (with Alliant Energy as guarantor) (c) 400 — — — — — AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a) 200 — — 200 — — AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a) 300 — — 300 — — AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)(d) 350 — — — — — Sheboygan Power, LLC 5.06% senior secured notes, due 2023 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 17 — — 24 — — AEF term loan credit agreement, 1% at December 31, 2021 (with Alliant Energy as guarantor) (Retired in 2022) — — — 300 — — Corporate Services 3.45% senior notes (Retired in 2022) — — — 75 — — Other, 1% at December 31, 2022, due 2023 to 2025 1 — — 1 — — 1,668 — — 1,300 — — Subtotal 8,143 3,675 2,800 7,425 3,675 2,450 Current maturities (408) — — (633) — (250) Unamortized debt issuance costs (45) (21) (19) (42) (23) (15) Unamortized debt (discount) and premium, net (22) (8) (11) (15) (9) (6) Long-term debt, net (e) $7,668 $3,646 $2,770 $6,735 $3,643 $2,179 (a) Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption. (b) In August 2022, WPL issued $600 million of 3.95% debentures due 2032. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds were disbursed for the development and acquisition of WPL’s solar EGUs. (c) In March 2022, AEF entered into a $300 million variable rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable rate term loan credit agreement that expired in March 2022. In December 2022, AEF increased the amount outstanding under the new term loan credit agreement by $100 million and used the additional borrowings to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026. Under the terms of the swap, AEF exchanged variable rate borrowings for a fixed rate of 3.93%. (d) In February 2022, AEF issued $350 million of 3.6% senior notes due 2032. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. (e) There were no significant sinking fund requirements related to the outstanding long-term debt.
Schedule of Maturities of Long-term Debt	At December 31, 2022, long-term debt maturities for 2023 through 2027 were as follows (in millions): 2023 2024 2025 2026 2027 IPL $— $500 $300 $— $— WPL — — — — 300 AEF 408 409 — 200 — Alliant Energy $408 $909 $300 $200 $300

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Leases [Line Items]
Schedule of Lease Details	Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12
Schedule of Operating Lease Liability Maturities	As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
Schedule of Finance Lease Liability Maturities	As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
IPL [Member]
Leases [Line Items]
Schedule of Lease Details	Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4%
Schedule of Operating Lease Liability Maturities	As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
WPL [Member]
Leases [Line Items]
Schedule of Lease Details	Operating lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $16 $9 $6 $14 $9 $5 Other current liabilities $3 $1 $1 $2 $1 $1 Other liabilities 13 8 5 12 8 4 Total operating lease liabilities $16 $9 $6 $14 $9 $5 Weighted average remaining lease term 10 years 11 years 9 years 9 years 11 years 8 years Weighted average discount rate 4% 4% 4% 4% 4% 4% Finance lease details are as follows (dollars in millions): December 31, 2022 December 31, 2021 Alliant Energy WPL Alliant Energy WPL Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $15 n/a $21 Leased land for solar generation $133 133 $11 11 $133 $148 $11 $32 Other current liabilities: Sheboygan Falls Energy Facility n/a $12 n/a $10 Leased land for solar generation $5 5 $1 1 5 17 1 11 Other liabilities: Sheboygan Falls Energy Facility n/a 19 n/a 31 Leased land for solar generation 131 131 11 11 131 150 11 42 Total finance lease liabilities $136 $167 $12 $53 Weighted average remaining lease term 34 years 28 years 34 years 10 years Weighted average discount rate 5% 5% 3% 9% Alliant Energy WPL 2022 2021 2020 2022 2021 2020 Depreciation and amortization expenses $— $— $— $6 $6 $6 Interest expense 3 — — 7 5 6 Total finance lease expense $3 $— $— $13 $11 $12
Schedule of Operating Lease Liability Maturities	As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167
Schedule of Finance Lease Liability Maturities	As of December 31, 2022, expected maturities of lease liabilities were as follows (in millions): 2023 2024 2025 2026 2027 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $3 $2 $2 $2 $2 $9 $20 $4 $16 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 2 7 1 6 Finance Leases: Alliant Energy 5 6 6 6 6 262 291 155 136 WPL 20 21 12 6 6 262 327 160 167

Revenues (Tables)

Revenues (Tables)	12 Months Ended
	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Disaggregation of 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 2022 2021 2020 2022 2021 2020 2022 2021 2020 Electric Utility: Retail - residential $1,233 $1,115 $1,093 $673 $620 $602 $560 $495 $491 Retail - commercial 821 763 718 536 508 474 285 255 244 Retail - industrial 965 893 841 538 505 488 427 388 353 Wholesale 233 187 168 64 57 57 169 130 111 Bulk power and other 169 123 100 48 62 74 121 61 26 Total Electric Utility 3,421 3,081 2,920 1,859 1,752 1,695 1,562 1,329 1,225 Gas Utility: Retail - residential 371 257 214 202 146 116 169 111 98 Retail - commercial 197 139 107 101 79 59 96 60 48 Retail - industrial 20 17 12 14 12 8 6 5 4 Transportation/other 54 43 40 34 28 25 20 15 15 Total Gas Utility 642 456 373 351 265 208 291 191 165 Other Utility: Steam 39 36 36 39 36 36 — — — Other utility 10 13 13 7 10 8 3 3 5 Total Other Utility 49 49 49 46 46 44 3 3 5 Non-Utility and Other: Travero and other 93 83 74 — — — — — — Total Non-Utility and Other 93 83 74 — — — — — — Total revenues $4,205 $3,669 $3,416 $2,256 $2,063 $1,947 $1,856 $1,523 $1,395
IPL [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of 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 2022 2021 2020 2022 2021 2020 2022 2021 2020 Electric Utility: Retail - residential $1,233 $1,115 $1,093 $673 $620 $602 $560 $495 $491 Retail - commercial 821 763 718 536 508 474 285 255 244 Retail - industrial 965 893 841 538 505 488 427 388 353 Wholesale 233 187 168 64 57 57 169 130 111 Bulk power and other 169 123 100 48 62 74 121 61 26 Total Electric Utility 3,421 3,081 2,920 1,859 1,752 1,695 1,562 1,329 1,225 Gas Utility: Retail - residential 371 257 214 202 146 116 169 111 98 Retail - commercial 197 139 107 101 79 59 96 60 48 Retail - industrial 20 17 12 14 12 8 6 5 4 Transportation/other 54 43 40 34 28 25 20 15 15 Total Gas Utility 642 456 373 351 265 208 291 191 165 Other Utility: Steam 39 36 36 39 36 36 — — — Other utility 10 13 13 7 10 8 3 3 5 Total Other Utility 49 49 49 46 46 44 3 3 5 Non-Utility and Other: Travero and other 93 83 74 — — — — — — Total Non-Utility and Other 93 83 74 — — — — — — Total revenues $4,205 $3,669 $3,416 $2,256 $2,063 $1,947 $1,856 $1,523 $1,395
WPL [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of 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 2022 2021 2020 2022 2021 2020 2022 2021 2020 Electric Utility: Retail - residential $1,233 $1,115 $1,093 $673 $620 $602 $560 $495 $491 Retail - commercial 821 763 718 536 508 474 285 255 244 Retail - industrial 965 893 841 538 505 488 427 388 353 Wholesale 233 187 168 64 57 57 169 130 111 Bulk power and other 169 123 100 48 62 74 121 61 26 Total Electric Utility 3,421 3,081 2,920 1,859 1,752 1,695 1,562 1,329 1,225 Gas Utility: Retail - residential 371 257 214 202 146 116 169 111 98 Retail - commercial 197 139 107 101 79 59 96 60 48 Retail - industrial 20 17 12 14 12 8 6 5 4 Transportation/other 54 43 40 34 28 25 20 15 15 Total Gas Utility 642 456 373 351 265 208 291 191 165 Other Utility: Steam 39 36 36 39 36 36 — — — Other utility 10 13 13 7 10 8 3 3 5 Total Other Utility 49 49 49 46 46 44 3 3 5 Non-Utility and Other: Travero and other 93 83 74 — — — — — — Total Non-Utility and Other 93 83 74 — — — — — — Total revenues $4,205 $3,669 $3,416 $2,256 $2,063 $1,947 $1,856 $1,523 $1,395

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax [Line Items]
Schedule of Components of Income Tax Expense (Benefit)	The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Current tax expense (benefit): Federal $7 $1 $1 ($29) ($21) $6 $46 $22 ($11) State 2 3 8 (8) (1) (1) 16 6 7 Deferred tax expense (benefit): Federal 109 9 22 91 73 30 10 (75) (9) State 28 15 8 1 — (2) 12 11 10 Production tax credits (123) (101) (95) (105) (87) (80) (18) (14) (15) Investment tax credits (1) (1) (1) — — — — (1) (1) $22 ($74) ($57) ($50) ($36) ($47) $66 ($51) ($19)
Schedule Of Effective Income Tax Rates	The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Statutory federal income tax rate 21% 21% 21% 21% 21% 21% 21% 21% 21% State income taxes, net of federal benefits 3 2 2 (2) (1) (1) 6 6 6 Production tax credits (18) (17) (17) (34) (27) (28) (5) (6) (7) Amortization of excess deferred taxes (Refer to Note 2 ) (2) (18) (13) (2) (4) (5) (3) (43) (26) Effect of rate-making on property-related differences (1) (1) (3) (1) (2) (4) (2) (1) (2) Adjustment for prior period taxes 1 1 1 1 2 1 — — — Other items, net (1) — (1) 1 — — — (1) — Overall income tax rate 3% (12%) (10%) (16%) (11%) (16%) 17% (24%) (8%)
Schedule of Deferred Tax Assets and Liabilities	The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Deferred tax liabilities: Property $2,442 $2,389 $1,440 $1,416 $938 $913 ATC Holdings 125 123 — — — — Other 155 111 86 76 80 50 Total deferred tax liabilities 2,722 2,623 1,526 1,492 1,018 963 Deferred tax assets: Federal credit carryforwards 672 560 450 345 209 192 Net operating losses carryforwards - federal — 39 — 36 — — Net operating losses carryforwards - state 32 38 — 3 — — Other 75 65 29 25 20 18 Subtotal deferred tax assets 779 702 479 409 229 210 Valuation allowances — (6) — — — — Total deferred tax assets 779 696 479 409 229 210 Total deferred tax liabilities, net $1,943 $1,927 $1,047 $1,083 $789 $753
Summary Of Tax Credit Carryforwards	At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2042 $527 $10 $1 Federal tax credits 2024-2042 672 450 209
Schedule Of Open Tax Years	Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2019 - 2021 Consolidated Iowa income tax returns (b) 2019 - 2021 Wisconsin combined tax returns (c) 2018 - 2021 (a) The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.
IPL [Member]
Income Tax [Line Items]
Schedule of Components of Income Tax Expense (Benefit)	The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Current tax expense (benefit): Federal $7 $1 $1 ($29) ($21) $6 $46 $22 ($11) State 2 3 8 (8) (1) (1) 16 6 7 Deferred tax expense (benefit): Federal 109 9 22 91 73 30 10 (75) (9) State 28 15 8 1 — (2) 12 11 10 Production tax credits (123) (101) (95) (105) (87) (80) (18) (14) (15) Investment tax credits (1) (1) (1) — — — — (1) (1) $22 ($74) ($57) ($50) ($36) ($47) $66 ($51) ($19)
Schedule Of Effective Income Tax Rates	The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Statutory federal income tax rate 21% 21% 21% 21% 21% 21% 21% 21% 21% State income taxes, net of federal benefits 3 2 2 (2) (1) (1) 6 6 6 Production tax credits (18) (17) (17) (34) (27) (28) (5) (6) (7) Amortization of excess deferred taxes (Refer to Note 2 ) (2) (18) (13) (2) (4) (5) (3) (43) (26) Effect of rate-making on property-related differences (1) (1) (3) (1) (2) (4) (2) (1) (2) Adjustment for prior period taxes 1 1 1 1 2 1 — — — Other items, net (1) — (1) 1 — — — (1) — Overall income tax rate 3% (12%) (10%) (16%) (11%) (16%) 17% (24%) (8%)
Schedule of Deferred Tax Assets and Liabilities	The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Deferred tax liabilities: Property $2,442 $2,389 $1,440 $1,416 $938 $913 ATC Holdings 125 123 — — — — Other 155 111 86 76 80 50 Total deferred tax liabilities 2,722 2,623 1,526 1,492 1,018 963 Deferred tax assets: Federal credit carryforwards 672 560 450 345 209 192 Net operating losses carryforwards - federal — 39 — 36 — — Net operating losses carryforwards - state 32 38 — 3 — — Other 75 65 29 25 20 18 Subtotal deferred tax assets 779 702 479 409 229 210 Valuation allowances — (6) — — — — Total deferred tax assets 779 696 479 409 229 210 Total deferred tax liabilities, net $1,943 $1,927 $1,047 $1,083 $789 $753
Summary Of Tax Credit Carryforwards	At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2042 $527 $10 $1 Federal tax credits 2024-2042 672 450 209
Schedule Of Open Tax Years	Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2019 - 2021 Consolidated Iowa income tax returns (b) 2019 - 2021 Wisconsin combined tax returns (c) 2018 - 2021 (a) The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.
WPL [Member]
Income Tax [Line Items]
Schedule of Components of Income Tax Expense (Benefit)	The components of “Income tax expense (benefit)” in the income statements were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Current tax expense (benefit): Federal $7 $1 $1 ($29) ($21) $6 $46 $22 ($11) State 2 3 8 (8) (1) (1) 16 6 7 Deferred tax expense (benefit): Federal 109 9 22 91 73 30 10 (75) (9) State 28 15 8 1 — (2) 12 11 10 Production tax credits (123) (101) (95) (105) (87) (80) (18) (14) (15) Investment tax credits (1) (1) (1) — — — — (1) (1) $22 ($74) ($57) ($50) ($36) ($47) $66 ($51) ($19)
Schedule Of Effective Income Tax Rates	The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Statutory federal income tax rate 21% 21% 21% 21% 21% 21% 21% 21% 21% State income taxes, net of federal benefits 3 2 2 (2) (1) (1) 6 6 6 Production tax credits (18) (17) (17) (34) (27) (28) (5) (6) (7) Amortization of excess deferred taxes (Refer to Note 2 ) (2) (18) (13) (2) (4) (5) (3) (43) (26) Effect of rate-making on property-related differences (1) (1) (3) (1) (2) (4) (2) (1) (2) Adjustment for prior period taxes 1 1 1 1 2 1 — — — Other items, net (1) — (1) 1 — — — (1) — Overall income tax rate 3% (12%) (10%) (16%) (11%) (16%) 17% (24%) (8%)
Schedule of Deferred Tax Assets and Liabilities	The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Deferred tax liabilities: Property $2,442 $2,389 $1,440 $1,416 $938 $913 ATC Holdings 125 123 — — — — Other 155 111 86 76 80 50 Total deferred tax liabilities 2,722 2,623 1,526 1,492 1,018 963 Deferred tax assets: Federal credit carryforwards 672 560 450 345 209 192 Net operating losses carryforwards - federal — 39 — 36 — — Net operating losses carryforwards - state 32 38 — 3 — — Other 75 65 29 25 20 18 Subtotal deferred tax assets 779 702 479 409 229 210 Valuation allowances — (6) — — — — Total deferred tax assets 779 696 479 409 229 210 Total deferred tax liabilities, net $1,943 $1,927 $1,047 $1,083 $789 $753
Summary Of Tax Credit Carryforwards	At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL State net operating losses 2025-2042 $527 $10 $1 Federal tax credits 2024-2042 672 450 209
Schedule Of Open Tax Years	Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows: Consolidated federal income tax returns (a) 2019 - 2021 Consolidated Iowa income tax returns (b) 2019 - 2021 Wisconsin combined tax returns (c) 2018 - 2021 (a) The 2019 and 2020 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date. (b) The statute of limitations for these Iowa tax returns expires three years from each filing date. (c) The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

Benefit Plans (Tables)

Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Assumptions Used To Measure Benefit Plans	The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.91% 2.57% 5.53% 2.81% 2.31% Discount rate for net periodic cost 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.40% 4.80% 4.50% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 9.22% 4.18% 4.76% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.30% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.55% 2.94% 2.61% 5.53% 2.80% 2.28% Discount rate for net periodic cost 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.50% 5.10% 4.50% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.94% 2.64% 5.53% 2.79% 2.27% Discount rate for net periodic cost 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 5.49% 4.02% 3.28% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A
Net Periodic Benefit Costs	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $9 $11 $11 $3 $4 $3 Interest cost 36 34 43 6 5 7 Expected return on plan assets (a) (69) (69) (70) (5) (5) (5) Amortization of prior service credit (b) (1) — — — — — Amortization of actuarial loss (c) 32 39 34 2 5 3 Settlement losses (d) 26 — 12 — — — $33 $15 $30 $6 $9 $8 IPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $6 $7 $7 $1 $1 $1 Interest cost 16 16 20 2 2 3 Expected return on plan assets (a) (31) (32) (33) (4) (3) (4) Amortization of actuarial loss (c) 13 17 15 1 2 1 Settlement losses (d) 13 — 7 — — — $17 $8 $16 $— $2 $1 WPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $3 $4 $4 $1 $1 $2 Interest cost 16 15 19 2 2 3 Expected return on plan assets (a) (31) (31) (31) (1) — (1) Amortization of prior service credit (b) — — — — — (1) Amortization of actuarial loss (c) 15 19 16 2 2 2 Settlement losses (d) 13 — — — — — $16 $7 $8 $4 $5 $5 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. (d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan.
Funded Status Of Benefit Plans	A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $1,251 $1,351 $210 $227 Service cost 9 11 3 4 Interest cost 36 34 6 5 Plan participants’ contributions — — 4 5 Actuarial gain (269) (46) (37) (12) Gross benefits paid (152) (99) (18) (19) Net benefit obligation at December 31 875 1,251 168 210 Change in plan assets: Fair value of plan assets at January 1 1,011 984 106 108 Actual return on plan assets (204) 87 (17) 4 Employer contributions 51 39 8 8 Plan participants’ contributions — — 4 5 Gross benefits paid (152) (99) (18) (19) Fair value of plan assets at December 31 706 1,011 83 106 Under funded status at December 31 ($169) ($240) ($85) ($104) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $9 $13 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (167) (238) (86) (109) Net amounts recognized at December 31 ($169) ($240) ($85) ($104) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $376 $429 $20 $38 Prior service credit (3) (4) — (1) $373 $425 $20 $37 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $567 $615 $84 $91 Service cost 6 7 1 1 Interest cost 16 16 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (123) (23) (14) (4) Gross benefits paid (77) (48) (7) (8) Net benefit obligation at December 31 389 567 68 84 Change in plan assets: Fair value of plan assets at January 1 462 453 74 74 Actual return on plan assets (92) 40 (12) 4 Employer contributions 51 17 1 2 Plan participants’ contributions — — 2 2 Gross benefits paid (77) (48) (7) (8) Fair value of plan assets at December 31 344 462 58 74 Under funded status at December 31 ($45) ($105) ($10) ($10) Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $6 $10 Current liabilities — — (2) (2) Pension and other benefit obligations (45) (105) (14) (18) Net amounts recognized at December 31 ($45) ($105) ($10) ($10) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $154 $180 $14 $13 Prior service credit (1) (1) — — $153 $179 $14 $13 Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $546 $588 $81 $89 Service cost 3 4 1 1 Interest cost 16 15 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (117) (18) (13) (5) Gross benefits paid (67) (43) (8) (8) Net benefit obligation at December 31 381 546 65 81 Change in plan assets: Fair value of plan assets at January 1 450 436 17 18 Actual return on plan assets (92) 39 (2) — Employer contributions — 18 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (67) (43) (8) (8) Fair value of plan assets at December 31 291 450 14 17 Under funded status at December 31 ($90) ($96) ($51) ($64) Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (5) (6) Pension and other benefit obligations (90) (96) (49) (61) Net amounts recognized at December 31 ($90) ($96) ($51) ($64) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $165 $188 $6 $18 Prior service credit — (1) — (1) $165 $187 $6 $17
Accumulated Benefit Obligations	Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Accumulated benefit obligations $857 $1,214 $168 $210 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 857 1,214 168 210 Fair value of plan assets 706 1,011 83 106 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 875 1,251 N/A N/A Fair value of plan assets 706 1,011 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Accumulated benefit obligations $379 $546 $68 $84 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 379 546 68 84 Fair value of plan assets 344 462 58 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 389 567 N/A N/A Fair value of plan assets 344 462 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Accumulated benefit obligations $373 $532 $65 $81 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 373 532 65 81 Fair value of plan assets 291 450 14 17 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 381 546 N/A N/A Fair value of plan assets 291 450 N/A N/A
Regulatory Assets	In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2022 2021 2022 2021 Regulatory assets $30 $35 $25 $30
Estimated Future Employer Contributions	Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2023 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $12 $1 $10 OPEB plans 8 2 6 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.
Expected Benefit Payments	Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $72 $71 $72 $74 $74 $349 OPEB 18 18 18 17 16 69 $90 $89 $90 $91 $90 $418 IPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $34 $33 $34 $33 $32 $155 OPEB 7 7 7 7 7 27 $41 $40 $41 $40 $39 $182 WPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $32 $31 $31 $31 $31 $148 OPEB 7 7 7 7 6 26 $39 $38 $38 $38 $37 $174
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 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Compensation expense $13 $14 $16 $7 $8 $9 $5 $6 $6 Income tax benefits 3 4 4 2 2 2 1 2 2
Schedule of Carrying Value and Fair Market Value of the Deferred Compensation Obligation	At December 31, the carrying value of the deferred compensation obligation for the company stock account and the shares in the deferred compensation trust based on the historical value of the shares of Alliant Energy common stock contributed to the rabbi trust, and the fair market value of the shares held in the rabbi trust, were as follows (in millions): 2022 2021 Carrying value $13 $12 Fair market value 22 24
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions Used To Measure Benefit Plans	The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.91% 2.57% 5.53% 2.81% 2.31% Discount rate for net periodic cost 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.40% 4.80% 4.50% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 9.22% 4.18% 4.76% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.30% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.55% 2.94% 2.61% 5.53% 2.80% 2.28% Discount rate for net periodic cost 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.50% 5.10% 4.50% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.94% 2.64% 5.53% 2.79% 2.27% Discount rate for net periodic cost 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 5.49% 4.02% 3.28% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A
Net Periodic Benefit Costs	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $9 $11 $11 $3 $4 $3 Interest cost 36 34 43 6 5 7 Expected return on plan assets (a) (69) (69) (70) (5) (5) (5) Amortization of prior service credit (b) (1) — — — — — Amortization of actuarial loss (c) 32 39 34 2 5 3 Settlement losses (d) 26 — 12 — — — $33 $15 $30 $6 $9 $8 IPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $6 $7 $7 $1 $1 $1 Interest cost 16 16 20 2 2 3 Expected return on plan assets (a) (31) (32) (33) (4) (3) (4) Amortization of actuarial loss (c) 13 17 15 1 2 1 Settlement losses (d) 13 — 7 — — — $17 $8 $16 $— $2 $1 WPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $3 $4 $4 $1 $1 $2 Interest cost 16 15 19 2 2 3 Expected return on plan assets (a) (31) (31) (31) (1) — (1) Amortization of prior service credit (b) — — — — — (1) Amortization of actuarial loss (c) 15 19 16 2 2 2 Settlement losses (d) 13 — — — — — $16 $7 $8 $4 $5 $5 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. (d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan.
Funded Status Of Benefit Plans	A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $1,251 $1,351 $210 $227 Service cost 9 11 3 4 Interest cost 36 34 6 5 Plan participants’ contributions — — 4 5 Actuarial gain (269) (46) (37) (12) Gross benefits paid (152) (99) (18) (19) Net benefit obligation at December 31 875 1,251 168 210 Change in plan assets: Fair value of plan assets at January 1 1,011 984 106 108 Actual return on plan assets (204) 87 (17) 4 Employer contributions 51 39 8 8 Plan participants’ contributions — — 4 5 Gross benefits paid (152) (99) (18) (19) Fair value of plan assets at December 31 706 1,011 83 106 Under funded status at December 31 ($169) ($240) ($85) ($104) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $9 $13 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (167) (238) (86) (109) Net amounts recognized at December 31 ($169) ($240) ($85) ($104) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $376 $429 $20 $38 Prior service credit (3) (4) — (1) $373 $425 $20 $37 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $567 $615 $84 $91 Service cost 6 7 1 1 Interest cost 16 16 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (123) (23) (14) (4) Gross benefits paid (77) (48) (7) (8) Net benefit obligation at December 31 389 567 68 84 Change in plan assets: Fair value of plan assets at January 1 462 453 74 74 Actual return on plan assets (92) 40 (12) 4 Employer contributions 51 17 1 2 Plan participants’ contributions — — 2 2 Gross benefits paid (77) (48) (7) (8) Fair value of plan assets at December 31 344 462 58 74 Under funded status at December 31 ($45) ($105) ($10) ($10) Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $6 $10 Current liabilities — — (2) (2) Pension and other benefit obligations (45) (105) (14) (18) Net amounts recognized at December 31 ($45) ($105) ($10) ($10) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $154 $180 $14 $13 Prior service credit (1) (1) — — $153 $179 $14 $13 Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $546 $588 $81 $89 Service cost 3 4 1 1 Interest cost 16 15 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (117) (18) (13) (5) Gross benefits paid (67) (43) (8) (8) Net benefit obligation at December 31 381 546 65 81 Change in plan assets: Fair value of plan assets at January 1 450 436 17 18 Actual return on plan assets (92) 39 (2) — Employer contributions — 18 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (67) (43) (8) (8) Fair value of plan assets at December 31 291 450 14 17 Under funded status at December 31 ($90) ($96) ($51) ($64) Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (5) (6) Pension and other benefit obligations (90) (96) (49) (61) Net amounts recognized at December 31 ($90) ($96) ($51) ($64) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $165 $188 $6 $18 Prior service credit — (1) — (1) $165 $187 $6 $17
Accumulated Benefit Obligations	Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Accumulated benefit obligations $857 $1,214 $168 $210 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 857 1,214 168 210 Fair value of plan assets 706 1,011 83 106 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 875 1,251 N/A N/A Fair value of plan assets 706 1,011 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Accumulated benefit obligations $379 $546 $68 $84 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 379 546 68 84 Fair value of plan assets 344 462 58 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 389 567 N/A N/A Fair value of plan assets 344 462 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Accumulated benefit obligations $373 $532 $65 $81 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 373 532 65 81 Fair value of plan assets 291 450 14 17 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 381 546 N/A N/A Fair value of plan assets 291 450 N/A N/A
Regulatory Assets	In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2022 2021 2022 2021 Regulatory assets $30 $35 $25 $30
Estimated Future Employer Contributions	Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2023 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $12 $1 $10 OPEB plans 8 2 6 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.
Expected Benefit Payments	Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $72 $71 $72 $74 $74 $349 OPEB 18 18 18 17 16 69 $90 $89 $90 $91 $90 $418 IPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $34 $33 $34 $33 $32 $155 OPEB 7 7 7 7 7 27 $41 $40 $41 $40 $39 $182 WPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $32 $31 $31 $31 $31 $148 OPEB 7 7 7 7 6 26 $39 $38 $38 $38 $37 $174
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 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Compensation expense $13 $14 $16 $7 $8 $9 $5 $6 $6 Income tax benefits 3 4 4 2 2 2 1 2 2
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions Used To Measure Benefit Plans	The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows: Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.91% 2.57% 5.53% 2.81% 2.31% Discount rate for net periodic cost 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.40% 4.80% 4.50% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 9.22% 4.18% 4.76% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.30% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.55% 2.94% 2.61% 5.53% 2.80% 2.28% Discount rate for net periodic cost 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 6.50% 5.10% 4.50% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2022 2021 2020 2022 2021 2020 Discount rate for benefit obligations 5.54% 2.94% 2.64% 5.53% 2.79% 2.27% Discount rate for net periodic cost 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Expected rate of return on plan assets 7.80% 7.10% 7.10% 5.49% 4.02% 3.28% Rate of compensation increase 3.30% 3.30% 3.65% N/A N/A N/A
Net Periodic Benefit Costs	The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $9 $11 $11 $3 $4 $3 Interest cost 36 34 43 6 5 7 Expected return on plan assets (a) (69) (69) (70) (5) (5) (5) Amortization of prior service credit (b) (1) — — — — — Amortization of actuarial loss (c) 32 39 34 2 5 3 Settlement losses (d) 26 — 12 — — — $33 $15 $30 $6 $9 $8 IPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $6 $7 $7 $1 $1 $1 Interest cost 16 16 20 2 2 3 Expected return on plan assets (a) (31) (32) (33) (4) (3) (4) Amortization of actuarial loss (c) 13 17 15 1 2 1 Settlement losses (d) 13 — 7 — — — $17 $8 $16 $— $2 $1 WPL Defined Benefit Pension Plans OPEB Plans 2022 2021 2020 2022 2021 2020 Service cost $3 $4 $4 $1 $1 $2 Interest cost 16 15 19 2 2 3 Expected return on plan assets (a) (31) (31) (31) (1) — (1) Amortization of prior service credit (b) — — — — — (1) Amortization of actuarial loss (c) 15 19 16 2 2 2 Settlement losses (d) 13 — — — — — $16 $7 $8 $4 $5 $5 (a) The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets. (b) Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan. (c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits. (d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan.
Funded Status Of Benefit Plans	A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $1,251 $1,351 $210 $227 Service cost 9 11 3 4 Interest cost 36 34 6 5 Plan participants’ contributions — — 4 5 Actuarial gain (269) (46) (37) (12) Gross benefits paid (152) (99) (18) (19) Net benefit obligation at December 31 875 1,251 168 210 Change in plan assets: Fair value of plan assets at January 1 1,011 984 106 108 Actual return on plan assets (204) 87 (17) 4 Employer contributions 51 39 8 8 Plan participants’ contributions — — 4 5 Gross benefits paid (152) (99) (18) (19) Fair value of plan assets at December 31 706 1,011 83 106 Under funded status at December 31 ($169) ($240) ($85) ($104) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $9 $13 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (167) (238) (86) (109) Net amounts recognized at December 31 ($169) ($240) ($85) ($104) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $376 $429 $20 $38 Prior service credit (3) (4) — (1) $373 $425 $20 $37 Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $567 $615 $84 $91 Service cost 6 7 1 1 Interest cost 16 16 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (123) (23) (14) (4) Gross benefits paid (77) (48) (7) (8) Net benefit obligation at December 31 389 567 68 84 Change in plan assets: Fair value of plan assets at January 1 462 453 74 74 Actual return on plan assets (92) 40 (12) 4 Employer contributions 51 17 1 2 Plan participants’ contributions — — 2 2 Gross benefits paid (77) (48) (7) (8) Fair value of plan assets at December 31 344 462 58 74 Under funded status at December 31 ($45) ($105) ($10) ($10) Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $6 $10 Current liabilities — — (2) (2) Pension and other benefit obligations (45) (105) (14) (18) Net amounts recognized at December 31 ($45) ($105) ($10) ($10) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $154 $180 $14 $13 Prior service credit (1) (1) — — $153 $179 $14 $13 Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Change in benefit obligation: Net benefit obligation at January 1 $546 $588 $81 $89 Service cost 3 4 1 1 Interest cost 16 15 2 2 Plan participants’ contributions — — 2 2 Actuarial gain (117) (18) (13) (5) Gross benefits paid (67) (43) (8) (8) Net benefit obligation at December 31 381 546 65 81 Change in plan assets: Fair value of plan assets at January 1 450 436 17 18 Actual return on plan assets (92) 39 (2) — Employer contributions — 18 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (67) (43) (8) (8) Fair value of plan assets at December 31 291 450 14 17 Under funded status at December 31 ($90) ($96) ($51) ($64) Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (5) (6) Pension and other benefit obligations (90) (96) (49) (61) Net amounts recognized at December 31 ($90) ($96) ($51) ($64) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $165 $188 $6 $18 Prior service credit — (1) — (1) $165 $187 $6 $17
Accumulated Benefit Obligations	Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions): Defined Benefit Pension Plans OPEB Plans Alliant Energy 2022 2021 2022 2021 Accumulated benefit obligations $857 $1,214 $168 $210 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 857 1,214 168 210 Fair value of plan assets 706 1,011 83 106 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 875 1,251 N/A N/A Fair value of plan assets 706 1,011 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2022 2021 2022 2021 Accumulated benefit obligations $379 $546 $68 $84 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 379 546 68 84 Fair value of plan assets 344 462 58 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 389 567 N/A N/A Fair value of plan assets 344 462 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2022 2021 2022 2021 Accumulated benefit obligations $373 $532 $65 $81 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 373 532 65 81 Fair value of plan assets 291 450 14 17 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 381 546 N/A N/A Fair value of plan assets 291 450 N/A N/A
Regulatory Assets	In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions): IPL WPL 2022 2021 2022 2021 Regulatory assets $30 $35 $25 $30
Estimated Future Employer Contributions	Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2023 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $12 $1 $10 OPEB plans 8 2 6 (a) Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.
Expected Benefit Payments	Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $72 $71 $72 $74 $74 $349 OPEB 18 18 18 17 16 69 $90 $89 $90 $91 $90 $418 IPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $34 $33 $34 $33 $32 $155 OPEB 7 7 7 7 7 27 $41 $40 $41 $40 $39 $182 WPL 2023 2024 2025 2026 2027 2028 - 2032 Defined benefit pension benefits $32 $31 $31 $31 $31 $148 OPEB 7 7 7 7 6 26 $39 $38 $38 $38 $37 $174
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 was as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 Compensation expense $13 $14 $16 $7 $8 $9 $5 $6 $6 Income tax benefits 3 4 4 2 2 2 1 2 2
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets By Asset Category, Fair Value Hierarchy Level and Allocations	At December 31, 2022, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 4% Equity securities - U.S. 14% - 61% 33% Equity securities - international 11% - 31% 21% Global asset securities 2% - 11% 5% Fixed income securities 27% - 47% 37% At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $79 $— $79 $— $35 $— $35 $— Equity securities - U.S. 185 185 — — 256 256 — — Global asset securities 35 35 — — 52 52 — — Fixed income securities 130 30 100 — 191 47 144 — Total assets in fair value hierarchy 429 $250 $179 $— 534 $355 $179 $— Assets measured at net asset value 276 477 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) — (1) Total pension plan assets $706 $1,011 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $62 $— $62 $— $16 $— $16 $— Equity securities - U.S. 83 83 — — 117 117 — — Global asset securities 16 16 — — 24 24 — — Fixed income securities 58 13 45 — 87 21 66 — Total assets in fair value hierarchy 219 $112 $107 $— 244 $162 $82 $— Assets measured at net asset value 124 218 Accrued investment income 1 — Total pension plan assets $344 $462 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $13 $— $13 $— $16 $— $16 $— Equity securities - U.S. 82 82 — — 114 114 — — Global asset securities 16 16 — — 23 23 — — Fixed income securities 57 13 44 — 85 21 64 — Total assets in fair value hierarchy 168 $111 $57 $— 238 $158 $80 $— Assets measured at net asset value 122 212 Accrued investment income 1 — Total pension plan assets $291 $450
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets By Asset Category, Fair Value Hierarchy Level and Allocations	At December 31, 2022, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 4% Equity securities - U.S. 14% - 61% 33% Equity securities - international 11% - 31% 21% Global asset securities 2% - 11% 5% Fixed income securities 27% - 47% 37% At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $79 $— $79 $— $35 $— $35 $— Equity securities - U.S. 185 185 — — 256 256 — — Global asset securities 35 35 — — 52 52 — — Fixed income securities 130 30 100 — 191 47 144 — Total assets in fair value hierarchy 429 $250 $179 $— 534 $355 $179 $— Assets measured at net asset value 276 477 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) — (1) Total pension plan assets $706 $1,011 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $62 $— $62 $— $16 $— $16 $— Equity securities - U.S. 83 83 — — 117 117 — — Global asset securities 16 16 — — 24 24 — — Fixed income securities 58 13 45 — 87 21 66 — Total assets in fair value hierarchy 219 $112 $107 $— 244 $162 $82 $— Assets measured at net asset value 124 218 Accrued investment income 1 — Total pension plan assets $344 $462 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $13 $— $13 $— $16 $— $16 $— Equity securities - U.S. 82 82 — — 114 114 — — Global asset securities 16 16 — — 23 23 — — Fixed income securities 57 13 44 — 85 21 64 — Total assets in fair value hierarchy 168 $111 $57 $— 238 $158 $80 $— Assets measured at net asset value 122 212 Accrued investment income 1 — Total pension plan assets $291 $450
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets By Asset Category, Fair Value Hierarchy Level and Allocations	At December 31, 2022, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 4% Equity securities - U.S. 14% - 61% 33% Equity securities - international 11% - 31% 21% Global asset securities 2% - 11% 5% Fixed income securities 27% - 47% 37% At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $79 $— $79 $— $35 $— $35 $— Equity securities - U.S. 185 185 — — 256 256 — — Global asset securities 35 35 — — 52 52 — — Fixed income securities 130 30 100 — 191 47 144 — Total assets in fair value hierarchy 429 $250 $179 $— 534 $355 $179 $— Assets measured at net asset value 276 477 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) — (1) Total pension plan assets $706 $1,011 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $62 $— $62 $— $16 $— $16 $— Equity securities - U.S. 83 83 — — 117 117 — — Global asset securities 16 16 — — 24 24 — — Fixed income securities 58 13 45 — 87 21 66 — Total assets in fair value hierarchy 219 $112 $107 $— 244 $162 $82 $— Assets measured at net asset value 124 218 Accrued investment income 1 — Total pension plan assets $344 $462 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $13 $— $13 $— $16 $— $16 $— Equity securities - U.S. 82 82 — — 114 114 — — Global asset securities 16 16 — — 23 23 — — Fixed income securities 57 13 44 — 85 21 64 — Total assets in fair value hierarchy 168 $111 $57 $— 238 $158 $80 $— Assets measured at net asset value 122 212 Accrued investment income 1 — Total pension plan assets $291 $450
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets By Asset Category, Fair Value Hierarchy Level and Allocations	At December 31, 2022, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 1% Equity securities - U.S. 0% - 55% 35% Fixed income securities 40% - 100% 64% At December 31, the fair values of OPEB plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $3 $— $3 $— $5 $— $5 $— Equity securities - U.S. 9 9 — — 11 11 — — Global asset securities 1 1 — — 1 1 — — Fixed income securities 47 46 1 — 60 58 2 — Total assets in fair value hierarchy 60 $56 $4 $— 77 $70 $7 $— Assets measured at net asset value 23 29 Total OPEB plan assets $83 $106 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $1 $— $1 $— $1 $— $1 $— Equity securities - U.S. 5 5 — — 8 8 — — Fixed income securities 34 34 — — 42 42 — — Total assets in fair value hierarchy 40 $39 $1 $— 51 $50 $1 $— Assets measured at net asset value 18 23 Total OPEB plan assets $58 $74 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $— $— $— $— $1 $— $1 $— Equity securities - U.S. 1 1 — — 1 1 — — Fixed income securities 13 13 — — 15 15 — — Total OPEB plan assets $14 $14 $— $— $17 $16 $1 $—
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets By Asset Category, Fair Value Hierarchy Level and Allocations	At December 31, 2022, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 1% Equity securities - U.S. 0% - 55% 35% Fixed income securities 40% - 100% 64% At December 31, the fair values of OPEB plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $3 $— $3 $— $5 $— $5 $— Equity securities - U.S. 9 9 — — 11 11 — — Global asset securities 1 1 — — 1 1 — — Fixed income securities 47 46 1 — 60 58 2 — Total assets in fair value hierarchy 60 $56 $4 $— 77 $70 $7 $— Assets measured at net asset value 23 29 Total OPEB plan assets $83 $106 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $1 $— $1 $— $1 $— $1 $— Equity securities - U.S. 5 5 — — 8 8 — — Fixed income securities 34 34 — — 42 42 — — Total assets in fair value hierarchy 40 $39 $1 $— 51 $50 $1 $— Assets measured at net asset value 18 23 Total OPEB plan assets $58 $74 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $— $— $— $— $1 $— $1 $— Equity securities - U.S. 1 1 — — 1 1 — — Fixed income securities 13 13 — — 15 15 — — Total OPEB plan assets $14 $14 $— $— $17 $16 $1 $—
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets By Asset Category, Fair Value Hierarchy Level and Allocations	At December 31, 2022, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows: Target Range Actual Allocation Allocation Cash and equivalents 0% - 5% 1% Equity securities - U.S. 0% - 55% 35% Fixed income securities 40% - 100% 64% At December 31, the fair values of OPEB plan assets were as follows (in millions): 2022 2021 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $3 $— $3 $— $5 $— $5 $— Equity securities - U.S. 9 9 — — 11 11 — — Global asset securities 1 1 — — 1 1 — — Fixed income securities 47 46 1 — 60 58 2 — Total assets in fair value hierarchy 60 $56 $4 $— 77 $70 $7 $— Assets measured at net asset value 23 29 Total OPEB plan assets $83 $106 2022 2021 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $1 $— $1 $— $1 $— $1 $— Equity securities - U.S. 5 5 — — 8 8 — — Fixed income securities 34 34 — — 42 42 — — Total assets in fair value hierarchy 40 $39 $1 $— 51 $50 $1 $— Assets measured at net asset value 18 23 Total OPEB plan assets $58 $74 2022 2021 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $— $— $— $— $1 $— $1 $— Equity securities - U.S. 1 1 — — 1 1 — — Fixed income securities 13 13 — — 15 15 — — Total OPEB plan assets $14 $14 $— $— $17 $16 $1 $—
401(k) Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employees Participate In Defined Contribution Retirement Plans	Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 401(k) costs $28 $26 $25 $13 $13 $13 $13 $12 $12
401(k) Savings Plan [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Employees Participate In Defined Contribution Retirement Plans	Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 401(k) costs $28 $26 $25 $13 $13 $13 $13 $12 $12
401(k) Savings Plan [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Employees Participate In Defined Contribution Retirement Plans	Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions): Alliant Energy IPL WPL 2022 2021 2020 2022 2021 2020 2022 2021 2020 401(k) costs $28 $26 $25 $13 $13 $13 $13 $12 $12
Performance Shares Equity Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of the performance shares activity, with amounts representing the target number of awards, was as follows: 2022 2021 2020 Shares Weighted Shares Weighted Shares Weighted Nonvested awards, January 1 196,429 $51.59 129,156 $54.63 74,193 $47.44 Granted 74,106 54.45 73,112 46.19 56,204 64.04 Vested (71,101) 47.48 — — — — Forfeited (9,161) 53.99 (5,839) 51.07 (1,241) 50.94 Nonvested awards, December 31 190,273 54.13 196,429 51.59 129,156 54.63
Restricted Stock Units Equity Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of the restricted stock units activity was as follows: 2022 2021 2020 Units Weighted Units Weighted Units Weighted Nonvested units, January 1 217,819 $50.54 146,549 $51.54 89,281 $46.04 Granted 77,122 56.88 80,152 48.65 61,056 59.42 Vested (82,770) 46.08 — — — — Forfeited (13,896) 55.53 (8,882) 49.84 (3,788) 49.01 Nonvested units, December 31 198,275 54.53 217,819 50.54 146,549 51.54
Performance Restricted Stock Units Equity Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of the performance restricted stock units activity, with amounts representing the target number of units, was as follows: 2022 2021 2020 Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Nonvested units, January 1 196,429 $50.74 197,463 $47.31 206,065 $41.50 Granted 84,670 57.01 73,112 48.66 56,204 59.37 Vested (71,101) 46.24 (68,307) 38.60 (63,565) 39.12 Forfeited (10,124) 55.92 (5,839) 50.46 (1,241) 49.25 Nonvested units, December 31 199,874 54.74 196,429 50.74 197,463 47.31

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2022
Schedule of Asset Retirement Obligations [Line Items]
Reconciliation Of Changes In Asset Retirement Obligations (AROs)	A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Balance, January 1 $294 $251 $213 $177 $81 $74 Revisions in estimated cash flows 19 50 15 44 4 6 Liabilities settled (48) (17) (39) (13) (9) (4) Liabilities incurred 6 3 — — 6 3 Accretion expense 8 7 6 5 2 2 Balance, December 31 $279 $294 $195 $213 $84 $81
IPL [Member]
Schedule of Asset Retirement Obligations [Line Items]
Reconciliation Of Changes In Asset Retirement Obligations (AROs)	A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Balance, January 1 $294 $251 $213 $177 $81 $74 Revisions in estimated cash flows 19 50 15 44 4 6 Liabilities settled (48) (17) (39) (13) (9) (4) Liabilities incurred 6 3 — — 6 3 Accretion expense 8 7 6 5 2 2 Balance, December 31 $279 $294 $195 $213 $84 $81
WPL [Member]
Schedule of Asset Retirement Obligations [Line Items]
Reconciliation Of Changes In Asset Retirement Obligations (AROs)	A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Balance, January 1 $294 $251 $213 $177 $81 $74 Revisions in estimated cash flows 19 50 15 44 4 6 Liabilities settled (48) (17) (39) (13) (9) (4) Liabilities incurred 6 3 — — 6 3 Accretion expense 8 7 6 5 2 2 Balance, December 31 $279 $294 $195 $213 $84 $81

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2022
Derivative [Line Items]
Notional Amounts of Derivative Instruments	As of December 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 1,132 2023-2025 9,046 2023 224,060 2023-2032 781 2023 IPL 589 2023-2025 3,999 2023 115,237 2023-2030 396 2023 WPL 543 2023 5,047 2023 108,823 2023-2032 385 2023
Fair Value of Financial Instruments	At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Current derivative assets $111 $113 $69 $48 $42 $65 Non-current derivative assets 126 63 69 36 57 27 Current derivative liabilities 59 8 40 4 19 4 Non-current derivative liabilities 20 1 6 — 14 1
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 at December 31 as follows: Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net 2022 Derivative assets $237 $193 $138 $108 $99 $85 Derivative liabilities 79 35 46 16 33 19 2021 Derivative assets 176 171 84 83 92 88 Derivative liabilities 9 4 4 3 5 1
IPL [Member]
Derivative [Line Items]
Notional Amounts of Derivative Instruments	As of December 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 1,132 2023-2025 9,046 2023 224,060 2023-2032 781 2023 IPL 589 2023-2025 3,999 2023 115,237 2023-2030 396 2023 WPL 543 2023 5,047 2023 108,823 2023-2032 385 2023
Fair Value of Financial Instruments	At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Current derivative assets $111 $113 $69 $48 $42 $65 Non-current derivative assets 126 63 69 36 57 27 Current derivative liabilities 59 8 40 4 19 4 Non-current derivative liabilities 20 1 6 — 14 1
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 at December 31 as follows: Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net 2022 Derivative assets $237 $193 $138 $108 $99 $85 Derivative liabilities 79 35 46 16 33 19 2021 Derivative assets 176 171 84 83 92 88 Derivative liabilities 9 4 4 3 5 1
WPL [Member]
Derivative [Line Items]
Notional Amounts of Derivative Instruments	As of December 31, 2022, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): Electricity FTRs Natural Gas Coal MWhs Years MWhs Years Dths Years Tons Years Alliant Energy 1,132 2023-2025 9,046 2023 224,060 2023-2032 781 2023 IPL 589 2023-2025 3,999 2023 115,237 2023-2030 396 2023 WPL 543 2023 5,047 2023 108,823 2023-2032 385 2023
Fair Value of Financial Instruments	At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions): Alliant Energy IPL WPL 2022 2021 2022 2021 2022 2021 Current derivative assets $111 $113 $69 $48 $42 $65 Non-current derivative assets 126 63 69 36 57 27 Current derivative liabilities 59 8 40 4 19 4 Non-current derivative liabilities 20 1 6 — 14 1
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 at December 31 as follows: Alliant Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net 2022 Derivative assets $237 $193 $138 $108 $99 $85 Derivative liabilities 79 35 46 16 33 19 2021 Derivative assets 176 171 84 83 92 88 Derivative liabilities 9 4 4 3 5 1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Recurring Fair Value Measurements	Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions): Alliant Energy 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 237 — 206 31 237 176 — 146 30 176 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 79 — 67 12 79 9 — 8 1 9 Long-term debt (incl. current maturities) 8,076 — 7,338 1 7,339 7,368 — 8,329 1 8,330 IPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 138 — 111 27 138 84 — 65 19 84 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 46 — 35 11 46 4 — 3 1 4 Long-term debt 3,646 — 3,228 — 3,228 3,643 — 4,124 — 4,124 WPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $99 $— $95 $4 $99 $92 $— $81 $11 $92 Liabilities and equity: Derivatives 33 — 32 1 33 5 — 5 — 5 Long-term debt (incl. current maturities) 2,770 — 2,542 — 2,542 2,429 — 2,862 — 2,862
Fair Value Measurements Using Significant Unobservable Inputs	Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (18) 6 — — Purchases 79 21 — — Sales (2) (1) — — Settlements (a) (69) (26) (29) 26 Ending balance, December 31 $19 $29 $185 $214 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($18) $6 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (12) (3) — — Purchases 58 16 — — Sales (1) (1) — — Settlements (a) (47) (20) (29) 26 Ending balance, December 31 $16 $18 $185 $214 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 December 31 ($13) ($3) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2022 2021 Beginning balance, January 1 $11 $3 Total net gains (losses) included in changes in net assets (realized/unrealized) (6) 9 Purchases 21 5 Sales (1) — Settlements (a) (22) (6) Ending balance, December 31 $3 $11 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($5) $9 (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 derivativ e assets (liabiliti es) at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2022 ($10) $29 ($9) $25 ($1) $4 2021 9 20 8 10 1 10
IPL [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Recurring Fair Value Measurements	Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions): Alliant Energy 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 237 — 206 31 237 176 — 146 30 176 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 79 — 67 12 79 9 — 8 1 9 Long-term debt (incl. current maturities) 8,076 — 7,338 1 7,339 7,368 — 8,329 1 8,330 IPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 138 — 111 27 138 84 — 65 19 84 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 46 — 35 11 46 4 — 3 1 4 Long-term debt 3,646 — 3,228 — 3,228 3,643 — 4,124 — 4,124 WPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $99 $— $95 $4 $99 $92 $— $81 $11 $92 Liabilities and equity: Derivatives 33 — 32 1 33 5 — 5 — 5 Long-term debt (incl. current maturities) 2,770 — 2,542 — 2,542 2,429 — 2,862 — 2,862
Fair Value Measurements Using Significant Unobservable Inputs	Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (18) 6 — — Purchases 79 21 — — Sales (2) (1) — — Settlements (a) (69) (26) (29) 26 Ending balance, December 31 $19 $29 $185 $214 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($18) $6 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (12) (3) — — Purchases 58 16 — — Sales (1) (1) — — Settlements (a) (47) (20) (29) 26 Ending balance, December 31 $16 $18 $185 $214 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 December 31 ($13) ($3) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2022 2021 Beginning balance, January 1 $11 $3 Total net gains (losses) included in changes in net assets (realized/unrealized) (6) 9 Purchases 21 5 Sales (1) — Settlements (a) (22) (6) Ending balance, December 31 $3 $11 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($5) $9 (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 derivativ e assets (liabiliti es) at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2022 ($10) $29 ($9) $25 ($1) $4 2021 9 20 8 10 1 10
WPL [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Recurring Fair Value Measurements	Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions): Alliant Energy 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 237 — 206 31 237 176 — 146 30 176 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 79 — 67 12 79 9 — 8 1 9 Long-term debt (incl. current maturities) 8,076 — 7,338 1 7,339 7,368 — 8,329 1 8,330 IPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $10 $10 $— $— $10 $32 $32 $— $— $32 Derivatives 138 — 111 27 138 84 — 65 19 84 Deferred proceeds 185 — — 185 185 214 — — 214 214 Liabilities and equity: Derivatives 46 — 35 11 46 4 — 3 1 4 Long-term debt 3,646 — 3,228 — 3,228 3,643 — 4,124 — 4,124 WPL 2022 2021 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $99 $— $95 $4 $99 $92 $— $81 $11 $92 Liabilities and equity: Derivatives 33 — 32 1 33 5 — 5 — 5 Long-term debt (incl. current maturities) 2,770 — 2,542 — 2,542 2,429 — 2,862 — 2,862
Fair Value Measurements Using Significant Unobservable Inputs	Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $29 $29 $214 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (18) 6 — — Purchases 79 21 — — Sales (2) (1) — — Settlements (a) (69) (26) (29) 26 Ending balance, December 31 $19 $29 $185 $214 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($18) $6 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2022 2021 2022 2021 Beginning balance, January 1 $18 $26 $214 $188 Total net losses included in changes in net assets (realized/unrealized) (12) (3) — — Purchases 58 16 — — Sales (1) (1) — — Settlements (a) (47) (20) (29) 26 Ending balance, December 31 $16 $18 $185 $214 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 December 31 ($13) ($3) $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2022 2021 Beginning balance, January 1 $11 $3 Total net gains (losses) included in changes in net assets (realized/unrealized) (6) 9 Purchases 21 5 Sales (1) — Settlements (a) (22) (6) Ending balance, December 31 $3 $11 The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($5) $9 (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 derivativ e assets (liabiliti es) at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2022 ($10) $29 ($9) $25 ($1) $4 2021 9 20 8 10 1 10

Commitments And Contingencies (

Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2022
Long-term Purchase Commitment [Line Items]
Other Purchase Commitments	At December 31, 2022, the related minimum future commitments were as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 Thereafter Total Natural gas $558 $297 $199 $136 $85 $209 $1,484 Coal 89 64 22 3 3 — 181 Other (a) 72 12 9 9 2 24 128 $719 $373 $230 $148 $90 $233 $1,793 IPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $319 $167 $85 $48 $36 $39 $694 Coal 45 26 20 3 3 — 97 Other (a) 28 2 2 2 2 22 58 $392 $195 $107 $53 $41 $61 $849 WPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $239 $130 $114 $88 $49 $170 $790 Coal 44 38 2 — — — 84 Other (a) 28 1 1 1 — — 31 $311 $169 $117 $89 $49 $170 $905 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2022.
Schedule of Environmental Liabilities	At December 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $9 - $25 $6 - $19 Current and non-current environmental liabilities $11 $8
IPL [Member]
Long-term Purchase Commitment [Line Items]
Other Purchase Commitments	At December 31, 2022, the related minimum future commitments were as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 Thereafter Total Natural gas $558 $297 $199 $136 $85 $209 $1,484 Coal 89 64 22 3 3 — 181 Other (a) 72 12 9 9 2 24 128 $719 $373 $230 $148 $90 $233 $1,793 IPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $319 $167 $85 $48 $36 $39 $694 Coal 45 26 20 3 3 — 97 Other (a) 28 2 2 2 2 22 58 $392 $195 $107 $53 $41 $61 $849 WPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $239 $130 $114 $88 $49 $170 $790 Coal 44 38 2 — — — 84 Other (a) 28 1 1 1 — — 31 $311 $169 $117 $89 $49 $170 $905 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2022.
Schedule of Environmental Liabilities	At December 31, 2022, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2022, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $9 - $25 $6 - $19 Current and non-current environmental liabilities $11 $8
WPL [Member]
Long-term Purchase Commitment [Line Items]
Other Purchase Commitments	At December 31, 2022, the related minimum future commitments were as follows (in millions): Alliant Energy 2023 2024 2025 2026 2027 Thereafter Total Natural gas $558 $297 $199 $136 $85 $209 $1,484 Coal 89 64 22 3 3 — 181 Other (a) 72 12 9 9 2 24 128 $719 $373 $230 $148 $90 $233 $1,793 IPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $319 $167 $85 $48 $36 $39 $694 Coal 45 26 20 3 3 — 97 Other (a) 28 2 2 2 2 22 58 $392 $195 $107 $53 $41 $61 $849 WPL 2023 2024 2025 2026 2027 Thereafter Total Natural gas $239 $130 $114 $88 $49 $170 $790 Coal 44 38 2 — — — 84 Other (a) 28 1 1 1 — — 31 $311 $169 $117 $89 $49 $170 $905 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2022.

Segments Of Business (Tables)

Segments Of Business (Tables)	12 Months Ended
	Dec. 31, 2022
Segment Reporting Information [Line Items]
Schedule of Segments of Business	Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions): ATC Holdings, Utility Non-utility, Alliant Energy 2022 Electric Gas Other Total Parent and Other Consolidated Revenues $3,421 $642 $49 $4,112 $93 $4,205 Depreciation and amortization 601 56 7 664 7 671 Operating income 805 97 3 905 23 928 Interest expense 269 56 325 Equity income from unconsolidated investments, net (1) — — (1) (50) (51) Income taxes 16 6 22 Net income attributable to Alliant Energy common shareowners 675 11 686 Total assets 16,571 1,631 860 19,062 1,101 20,163 Investments in equity method subsidiaries 20 — — 20 522 542 Construction and acquisition expenditures 1,318 74 — 1,392 92 1,484 ATC Holdings, Utility Non-utility, Alliant Energy 2021 Electric Gas Other Total Parent and Other Consolidated Revenues $3,081 $456 $49 $3,586 $83 $3,669 Depreciation and amortization 591 54 6 651 6 657 Operating income (loss) 716 63 (11) 768 27 795 Interest expense 244 33 277 Equity income from unconsolidated investments, net (2) — — (2) (60) (62) Income tax expense (benefit) (87) 13 (74) Net income attributable to Alliant Energy common shareowners 618 41 659 Total assets 14,924 1,487 1,103 17,514 1,039 18,553 Investments in equity method subsidiaries 17 — — 17 491 508 Construction and acquisition expenditures 980 90 — 1,070 99 1,169 ATC Holdings, Utility Non-utility, Alliant Energy 2020 Electric Gas Other Total Parent and Other Consolidated Revenues $2,920 $373 $49 $3,342 $74 $3,416 Depreciation and amortization 556 49 5 610 5 615 Operating income (loss) 643 74 (1) 716 24 740 Interest expense 243 32 275 Equity income from unconsolidated investments, net (2) — — (2) (59) (61) Income tax expense (benefit) (66) 9 (57) Net income attributable to Alliant Energy common shareowners 573 41 614 Total assets 14,358 1,413 990 16,761 949 17,710 Investments in equity method subsidiaries 11 — — 11 465 476 Construction and acquisition expenditures 1,109 182 2 1,293 73 1,366
IPL [Member]
Segment Reporting Information [Line Items]
Schedule of Segments of Business	Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,859 $351 $46 $2,256 Depreciation and amortization 342 32 7 381 Operating income 397 53 3 453 Interest expense 148 Income tax benefit (50) Net income available for common stock 360 Total assets 8,686 872 517 10,075 Construction and acquisition expenditures 336 36 — 372 2021 Electric Gas Other Total Revenues $1,752 $265 $46 $2,063 Depreciation and amortization 338 31 6 375 Operating income (loss) 420 43 (3) 460 Interest expense 139 Income tax benefit (36) Net income available for common stock 350 Total assets 8,602 819 575 9,996 Construction and acquisition expenditures 342 42 — 384 2020 Electric Gas Other Total Revenues $1,695 $208 $44 $1,947 Depreciation and amortization 321 30 5 356 Operating income 358 50 2 410 Interest expense 139 Income tax benefit (47) Net income available for common stock 324 Total assets 8,518 766 565 9,849 Construction and acquisition expenditures 626 59 2 687
WPL [Member]
Segment Reporting Information [Line Items]
Schedule of Segments of Business	Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions): 2022 Electric Gas Other Total Revenues $1,562 $291 $3 $1,856 Depreciation and amortization 259 24 — 283 Operating income 408 44 — 452 Interest expense 121 Income taxes 66 Net income 315 Total assets 7,885 759 343 8,987 Construction and acquisition expenditures 982 38 — 1,020 2021 Electric Gas Other Total Revenues $1,329 $191 $3 $1,523 Depreciation and amortization 253 23 — 276 Operating income (loss) 296 20 (8) 308 Interest expense 105 Income tax benefit (51) Net income 268 Total assets 6,322 668 528 7,518 Construction and acquisition expenditures 638 48 — 686 2020 Electric Gas Other Total Revenues $1,225 $165 $5 $1,395 Depreciation and amortization 235 19 — 254 Operating income (loss) 285 24 (3) 306 Interest expense 104 Income tax benefit (19) Net income 249 Total assets 5,840 647 425 6,912 Construction and acquisition expenditures 483 123 — 606

Related Parties (Tables)

Related Parties (Tables)	12 Months Ended
	Dec. 31, 2022
Related Party Transaction [Line Items]
Services Provided, Sales Credited And Purchases Billed	The amounts billed for services provided, sales credited and purchases were as follows (in millions): IPL WPL 2022 2021 2020 2022 2021 2020 Corporate Services billings $181 $180 $176 $155 $154 $142 Sales credited 19 22 35 74 23 3 Purchases billed 435 441 329 174 116 108
Net Intercompany Payables	As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2022 2021 IPL $103 $110 WPL 56 83
Related Amounts Billed Between Parties	The related amounts billed between the parties were as follows (in millions): 2022 2021 2020 ATC billings to WPL $140 $122 $108 WPL billings to ATC 18 18 10
IPL [Member]
Related Party Transaction [Line Items]
Services Provided, Sales Credited And Purchases Billed	The amounts billed for services provided, sales credited and purchases were as follows (in millions): IPL WPL 2022 2021 2020 2022 2021 2020 Corporate Services billings $181 $180 $176 $155 $154 $142 Sales credited 19 22 35 74 23 3 Purchases billed 435 441 329 174 116 108
Net Intercompany Payables	As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2022 2021 IPL $103 $110 WPL 56 83
WPL [Member]
Related Party Transaction [Line Items]
Services Provided, Sales Credited And Purchases Billed	The amounts billed for services provided, sales credited and purchases were as follows (in millions): IPL WPL 2022 2021 2020 2022 2021 2020 Corporate Services billings $181 $180 $176 $155 $154 $142 Sales credited 19 22 35 74 23 3 Purchases billed 435 441 329 174 116 108
Net Intercompany Payables	As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2022 2021 IPL $103 $110 WPL 56 83
Related Amounts Billed Between Parties	The related amounts billed between the parties were as follows (in millions): 2022 2021 2020 ATC billings to WPL $140 $122 $108 WPL billings to ATC 18 18 10

Condensed Parent Company Fina_2

Condensed Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2022
Condensed Financial Information Disclosure [Abstract]
Condensed Statements of Income	ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF INCOME 2022 2021 2020 (in millions) Operating expenses $9 $5 $7 Operating loss (9) (5) (7) Other (income) and deductions: Equity earnings from consolidated subsidiaries (707) (664) (625) Interest expense 6 1 2 Other 1 1 4 Total other (income) and deductions (700) (662) (619) Income before income taxes 691 657 612 Income tax expense (benefit) 2 (5) (4) Net income $689 $662 $616 Refer to accompanying Notes to Condensed Financial Statements.
Condensed Balance Sheets	ALLIANT ENERGY CORPORATION (Parent Company Only) December 31, CONDENSED BALANCE SHEETS 2022 2021 (in millions) ASSETS Current assets: Notes receivable from affiliated companies $65 $16 Other 1 5 Total current assets 66 21 Investments: Investments in consolidated subsidiaries 7,801 7,061 Other 2 2 Total investments 7,803 7,063 Other assets 97 96 Total assets $7,966 $7,180 LIABILITIES AND EQUITY Current liabilities: Commercial paper $352 $279 Notes payable to affiliated companies 1,318 900 Other 10 4 Total current liabilities 1,680 1,183 Other liabilities 1 2 Common equity: Common stock and additional paid-in capital 2,780 2,752 Retained earnings 3,518 3,255 Shares in deferred compensation trust (13) (12) Total common equity 6,285 5,995 Total liabilities and equity $7,966 $7,180 Refer to accompanying Notes to Condensed Financial Statements.
Condensed Statements of Cash Flows	ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF CASH FLOWS 2022 2021 2020 (in millions) Net cash flows from operating activities $492 $494 $396 Cash flows used for investing activities: Capital contributions to consolidated subsidiaries (530) (295) (429) Net change in notes receivable from and payable to affiliates 369 (21) 201 Dividends from consolidated subsidiaries in excess of equity earnings — 50 — Net cash flows used for investing activities (161) (266) (228) Cash flows used for financing activities: Common stock dividends (428) (403) (377) Proceeds from issuance of common stock, net 25 28 247 Net change in commercial paper 73 147 (37) Other (1) — (1) Net cash flows used for financing activities (331) (228) (168) Net increase (decrease) in cash, cash equivalents and restricted cash — — — Cash, cash equivalents and restricted cash at beginning of period — — — Cash, cash equivalents and restricted cash at end of period $— $— $— Supplemental cash flows information: Cash (paid) refunded during the period for: Interest ($6) ($1) ($2) Income taxes, net $15 $4 $10 Refer to accompanying Notes to Condensed Financial Statements.

Summary Of Significant Accoun_4

Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2024 MWd	Dec. 31, 2023	Dec. 31, 2022 USD ($) customer MW	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Current Expected Credit Losses Estimates:
New accounting standard, cumulative effect adjustment to retained earnings, after-tax					$ (3,509)	$ (3,250)
Variable Interest Entities
Distributions to noncontrolling interest					$ 29	0	$ 0
Non-utility wind farm in Oklahoma [Member]
General:
Ownership interest					50%
Cumulative Effect, Period of Adoption, Adjustment [Member]
Current Expected Credit Losses Estimates:
New accounting standard, cumulative effect adjustment to retained earnings, pre-tax							12
New accounting standard, cumulative effect adjustment to retained earnings, after-tax							9	$ 9
IPL [Member]
General:
Generation and distribution of steam, number of customers served (in customers) | customer					2
Electric capacity of wind farm (in megawatts) | MW					1,000
Property, Plant and Equipment:
AFUDC accrual recorded, percentage of estimated CWIP					100%
Current Expected Credit Losses Estimates:
New accounting standard, cumulative effect adjustment to retained earnings, after-tax					$ (968)	(929)
WPL [Member]
Property, Plant and Equipment:
AFUDC accrual recorded, percentage of estimated CWIP					50%
AFUDC accrual recorded, percentage earning a return as part of rate base					50%
AFUDC rates, projects with approval					100%
Current Expected Credit Losses Estimates:
New accounting standard, cumulative effect adjustment to retained earnings, after-tax					$ (1,192)	(1,053)
Variable Interest Entities
WPL's cash contribution		$ 62
Tax equity partner's cash contribution		29
Contributed funds paid to WPL for equity interests		$ 88
Distributions to noncontrolling interest	$ 29				$ 29	$ 0	$ 0
Alliant Energy Finance, LLC [Member]
General:
Electric capacity of wind farm (in megawatts) | MW					225
Alliant Energy Finance, LLC [Member] | Non-utility wind farm in Oklahoma [Member]
General:
Ownership interest					50%
Sheboygan Falls Energy Facility [Member]
General:
Fossil-fueled EGU capacity (in megawatts) | MW					347
Finance lease, lease term					20 years
Electric Generation Equipment [Member] | IPL [Member]
Property, Plant and Equipment:
Average rate of depreciation					3.40%	3.40%	3.50%
Electric Generation Equipment [Member] | WPL [Member]
Property, Plant and Equipment:
Average rate of depreciation					3.40%	3.50%	3.50%
Distribution [Member] | IPL [Member]
Property, Plant and Equipment:
Average rate of depreciation					2.80%	2.90%	2.80%
Distribution [Member] | WPL [Member]
Property, Plant and Equipment:
Average rate of depreciation					2.50%	2.60%	2.60%
Gas [Member] | IPL [Member]
Property, Plant and Equipment:
Average rate of depreciation					3.30%	3.30%	3.30%
Gas [Member] | WPL [Member]
Property, Plant and Equipment:
Average rate of depreciation					2.40%	2.40%	2.40%
Forecast [Member] | Solar [Member] | WPL [Member]
Variable Interest Entities
Nameplate capacity (in MWs) | MWd			1,100
Forecast [Member] | Electric Generation Equipment [Member] | WPL [Member]
Property, Plant and Equipment:
Average rate of depreciation				3.60%
Forecast [Member] | Distribution [Member] | WPL [Member]
Property, Plant and Equipment:
Average rate of depreciation				2.70%
Forecast [Member] | Gas [Member] | WPL [Member]
Property, Plant and Equipment:
Average rate of depreciation				2.90%

Summary Of Significant Accoun_5

Summary Of Significant Accounting Policies (Schedule Of Average Rates Of Depreciation) (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Electric - generation [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.40%	3.40%	3.50%
Electric - generation [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.40%	3.50%	3.50%
Electric - distribution [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.80%	2.90%	2.80%
Electric - distribution [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.50%	2.60%	2.60%
Electric - other [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	5.70%	5.70%	5.20%
Electric - other [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	6.80%	7.40%	6.10%
Gas [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.30%	3.30%	3.30%
Gas [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.40%	2.40%	2.40%
Other [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	6.10%	6.10%	6.30%
Other [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	4.90%	5.40%	5.90%

Summary Of Significant Accoun_6

Summary Of Significant Accounting Policies (Schedule Of Allowance For Funds Used During Construction Recovery Rate) (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
IPL [Member] | IPL (Wind generation CWIP) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	6.90%	7%	7.10%
IPL [Member] | IPL (other CWIP) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	7%	7.20%	7.20%
WPL [Member] | WPL (retail jurisdiction) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	7%	7%	7%
WPL [Member] | WPL (wholesale jurisdiction) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	6.20%	5.60%	6.30%

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2020 customer	Dec. 31, 2022 USD ($) MW	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Regulatory Matters [Line Items]
Regulatory assets		$ 2,046	$ 1,940
Credits issued to customers		22	(66)	$ (113)
Regulatory liabilities		1,324	1,271
Electric transmission cost recovery [Member]
Regulatory Matters [Line Items]
Regulatory liabilities		20	51
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return		66
Regulatory assets		1,386	1,443
Credits issued to customers		$ 53	1	(20)
Electric capacity of wind farm (in megawatts) | MW		1,000
Regulatory liabilities		$ 754	691
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Matters [Line Items]
Credits issued to customers				42
Regulatory liabilities		10	27
IPL [Member] | Derecho windstorm [Member]
Regulatory Matters [Line Items]
Number of customers without power, derecho windstorm (number of customers) | customer	250,000
Derecho windstorm repair and rebuilding costs		140
Net regulatory liability, derecho windstorm		8
WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return		28
Regulatory assets		660	497
Credits issued to customers		(31)	(67)	(93)
Regulatory liabilities		570	580
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Matters [Line Items]
Regulatory liabilities		10	$ 24
2021 Test Period Fuel-related Costs [Member] | WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets		37
2022 Test Period Fuel-related Costs [Member] | WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets		117
2020 Test Period Retail Electric [Member] | IPL [Member]
Regulatory Matters [Line Items]
Interim rate increase (decrease), amount					$ 90
Authorized increase (decrease) in final rates, amount				127
2020 Test Period Retail Electric [Member] | IPL [Member] | Tax-related [Member]
Regulatory Matters [Line Items]
Regulatory liabilities		27
2020 Test Period Retail Electric [Member] | IPL [Member] | Revenue Subject to Refund [Member]
Regulatory Matters [Line Items]
Regulatory liabilities		8
2020 Test Period Retail Gas [Member] | IPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount				12
2019 Test Period Retail Electric [Member] | WPL [Member] | Revenue Subject to Refund [Member]
Regulatory Matters [Line Items]
Credits issued to customers				12
2022 Test Period Retail Electric [Member] | WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		114
2022 Test Period Retail Gas [Member] | WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount		$ 15
DAEC PPA [Member]
Regulatory Matters [Line Items]
Buyout payment				$ 110
PPA term amendment		5 years

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Regulatory Assets [Line Items]
Regulatory assets	$ 2,046	$ 1,940
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	929	934
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	392	462
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	160	42
AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	151	128
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	84	8
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	70	92
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	90
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	52
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	146	132
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,386	1,443
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	848	884
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	197	228
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	1	2
IPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	110	89
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	4
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	53	66
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	90
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	63	80
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	660	497
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	81	50
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	195	234
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	159	40
WPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	41	39
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	36	4
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	17	26
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	52
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 83	$ 52

Regulatory Matters (Assets Reti

Regulatory Matters (Assets Retired Early) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Regulatory Assets [Line Items]
Regulatory assets	$ 2,046	$ 1,940
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	70	92
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,386	1,443
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	53	66
IPL [Member] | Assets retired early [Member] | Sutherland Units 1 and 3 [Member]
Regulatory Assets [Line Items]
Regulatory assets	16
IPL [Member] | Assets retired early [Member] | M.L. Kapp Unit 2 [Member]
Regulatory Assets [Line Items]
Regulatory assets	13
IPL [Member] | Assets retired early [Member] | Analog Electric Meters [Member]
Regulatory Assets [Line Items]
Regulatory assets	24
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	660	497
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	17	$ 26
WPL [Member] | Assets retired early [Member] | Edgewater Unit 4 [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 17

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,324	$ 1,271
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	579	585
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	398	384
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	210	166
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	40	17
West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	32	36
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	20	51
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	45	32
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	754	691
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	303	312
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	259	252
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	115	77
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	38	15
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	10	27
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	29	8
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	570	580
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	276	273
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	139	132
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	95	89
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	2	2
WPL [Member] | West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	32	36
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	10	24
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 16	$ 24

Property, Plant and Equipment_2

Property, Plant and Equipment (Narrative) (Details)	12 Months Ended
	Dec. 31, 2022
Corporate Services [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Corporate Services [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	30 years
Sheboygan Falls Energy Facility [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	35 years
Customer Billing And Information System [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	12 years
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years

Property, Plant and Equipment_3

Property, Plant and Equipment (Property, Plant and Equipment) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	$ 2,103	$ 2,094
Total electric plant	17,618	16,710
Gas plant in service	1,705	1,636
Other plant in service	624	621
Accumulated depreciation	(5,690)	(5,263)
Net plant	14,257	13,704
Leased land for solar generation, net	133	11
Construction work in progress	1,357	778
Other, net	6	7
Total utility	15,753	14,500
Non-utility Generation, net	71	75
Corporate Services and other, net	423	412
Total non-utility and other	494	487
Total property, plant and equipment	16,247	14,987
Non-utility Generation, accumulated depreciation	71	67
Corporate Services and other, accumulated depreciation	269	245
Generation [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	8,060	7,539
Distribution [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	6,912	6,537
Other [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	543	540
IPL [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	491	487
Total electric plant	9,683	9,424
Gas plant in service	910	878
Other plant in service	402	398
Accumulated depreciation	(3,149)	(2,897)
Net plant	7,846	7,803
Leased land for solar generation, net	0	0
Construction work in progress	194	174
Other, net	6	6
Total utility	8,046	7,983
Total property, plant and equipment	8,046	7,983
IPL [Member] | Lansing [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	233
IPL [Member] | Generation [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	4,962	4,922
IPL [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	3,876	3,652
IPL [Member] | Other [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	354	363
WPL [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	1,612	1,607
Total electric plant	7,935	7,286
Gas plant in service	795	758
Other plant in service	222	223
Accumulated depreciation	(2,541)	(2,366)
Net plant	6,411	5,901
Leased Sheboygan Falls Energy Facility, net	15	21
Leased land for solar generation, net	133	11
Construction work in progress	1,163	604
Other, net	0	1
Total utility	7,722	6,538
Total property, plant and equipment	7,722	6,538
Leased Sheboygan Falls Energy Facility, accumulated depreciation	106	100
WPL [Member] | Edgewater Unit 5 [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	511
WPL [Member] | Columbia Units 1-2 [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	440
WPL [Member] | Generation [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	3,098	2,617
WPL [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	3,036	2,885
WPL [Member] | Other [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	$ 189	$ 177

Property, Plant and Equipment_4

Property, Plant and Equipment (Equity and Debt AFUDC) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	$ 60	$ 25	$ 55
Equity [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	44	18	39
Debt [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	16	7	16
IPL [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	11	9	24
IPL [Member] | Equity [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	8	7	17
IPL [Member] | Debt [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	3	2	7
WPL [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	49	16	31
WPL [Member] | Equity [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	36	11	22
WPL [Member] | Debt [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	$ 13	$ 5	$ 9

Jointly-Owned Electric Utilit_3

Jointly-Owned Electric Utility Plant (Details) $ in Millions	Dec. 31, 2022 USD ($)
Jointly Owned Electric Utility Plant [Line Items]
Electric Plant	$ 2,663
Accumulated Provision for Depreciation	886
Construction Work in Progress	42
IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Electric Plant	1,024
Accumulated Provision for Depreciation	445
Construction Work in Progress	27
WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Electric Plant	1,639
Accumulated Provision for Depreciation	441
Construction Work in Progress	$ 15
Ottumwa Unit 1 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	48%
Electric Plant	$ 612
Accumulated Provision for Depreciation	241
Construction Work in Progress	$ 17
George Neal Unit 4 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	25.70%
Electric Plant	$ 193
Accumulated Provision for Depreciation	103
Construction Work in Progress	$ 4
George Neal Unit 3 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	28%
Electric Plant	$ 176
Accumulated Provision for Depreciation	80
Construction Work in Progress	$ 6
Louisa Unit 1 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	4%
Electric Plant	$ 43
Accumulated Provision for Depreciation	21
Construction Work in Progress	$ 0
Columbia Units 1-2 [Member] | WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	53.50%
Electric Plant	$ 805
Accumulated Provision for Depreciation	338
Construction Work in Progress	$ 13
West Riverside [Member] | WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	91%
Electric Plant	$ 716
Accumulated Provision for Depreciation	53
Construction Work in Progress	$ 2
Forward Wind Energy Center [Member] | WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	42.60%
Electric Plant	$ 118
Accumulated Provision for Depreciation	50
Construction Work in Progress	$ 0

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) $ in Millions	Dec. 31, 2022 USD ($)
Maximum [Member]
Accounts Receivable [Line Items]
Limit on cash proceeds to be received from third-party	$ 110
Financing Receivable [Member] | IPL [Member]
Accounts Receivable [Line Items]
Available capacity	$ 30

Receivables (Details of Account

Receivables (Details of Accounts Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Accounts Receivable [Line Items]
Customer	$ 114	$ 93
Unbilled utility revenues	115	91
Deferred proceeds	185	214
Other	109	53
Allowance for expected credit losses	(7)	(11)
Accounts receivable, less allowance for expected credit losses	516	440
IPL [Member]
Accounts Receivable [Line Items]
Customer	0	0
Unbilled utility revenues	0	0
Deferred proceeds	185	214
Other	74	28
Allowance for expected credit losses	0	(1)
Accounts receivable, less allowance for expected credit losses	259	241
WPL [Member]
Accounts Receivable [Line Items]
Customer	102	82
Unbilled utility revenues	115	91
Other	34	25
Allowance for expected credit losses	(7)	(10)
Accounts receivable, less allowance for expected credit losses	$ 244	$ 188

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Maximum [Member]
Accounts Receivable [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 80	$ 110	$ 96
Average [Member]
Accounts Receivable [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 14	$ 46	$ 9

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Accounts Receivable [Line Items]
Fair value of deferred proceeds	$ 185	$ 214
IPL [Member]
Accounts Receivable [Line Items]
Fair value of deferred proceeds	185	214
Financing Receivable [Member] | IPL [Member]
Accounts Receivable [Line Items]
Customer accounts receivable	145	125
Unbilled utility revenues	132	104
Receivables sold to third party	277	229
Less: cash proceeds	80	1
Deferred proceeds	197	228
Less: allowance for expected credit losses	12	14
Fair value of deferred proceeds	185	214
Outstanding receivables past due	$ 26	$ 22

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable [Line Items]
Collections	$ 2,302	$ 2,134	$ 2,025
Write-offs, net of recoveries	$ 9	$ 9	$ 7

Investments (Narrative) (Detail

Investments (Narrative) (Details)	Dec. 31, 2022
ATC LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	16%
ATC Holdco LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	20%

Investments (Unconsolidated Equ

Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Carrying value	$ 542	$ 508	$ 476
Equity (income) / loss	(51)	(62)	(61)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	358	338
Equity (income) / loss	$ (41)	(43)	(47)
ATC LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	16%
ATC Holdco LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	20%
Non-utility wind farm in Oklahoma [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	50%
Carrying value	$ 101	99
Equity (income) / loss	(5)	(4)	(8)
Corporate venture investments [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	62	52
Equity (income) / loss	(3)	(13)	(4)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	21	19
Equity (income) / loss	(2)	(2)	(2)
Total [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	542	508
Equity (income) / loss	$ (51)	$ (62)	$ (61)

Investments (Summary Financial

Investments (Summary Financial Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues	$ 4,205	$ 3,669	$ 3,416
Current assets	1,250	1,069
Current liabilities	2,363	2,054
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Revenues	813	802	801
Operating income	350	357	376
Net income	675	358	$ 343
Current assets	227	112
Non-current assets	8,292	7,036
Current liabilities	620	455
Non-current liabilities	3,285	3,110
Noncontrolling interest	$ 289	$ 247

Common Equity (Narrative) (Deta

Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Common Equity [Line Items]
Shares available for issuance under the 2020 OIP, Shareowner Direct Plan and 401(k) Savings Plan (in shares)		13,000,000
Proceeds from issuance of common stock, net		$ 25	$ 28	$ 247
Equity Forward Agreements [Member]
Schedule of Common Equity [Line Items]
Proceeds from issuance of common stock, net				$ 222
Common stock issued during the period (in shares)		0	0	4,275,127
Initial forward sale price (in dollars per share)				$ 51.98
Forecast [Member] | At-the-market Offering Program [Member]
Schedule of Common Equity [Line Items]
Proceeds from issuance of common stock, net	$ 225

Common Equity (Common Share Act

Common Equity (Common Share Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1 (in shares)	250,474,529	249,868,415	245,022,800
Common stock issued during the period, Shareowner Direct Plan (in shares)	437,669	492,565	472,283
Common stock issued during the period, Equity-based compensation plans (in shares)	222,768	113,549	98,205
Shares outstanding, December 31 (in shares)	251,134,966	250,474,529	249,868,415
Equity Forward Agreements [Member]
Common Stock Oustanding [Roll Forward]
Common stock issued during the period (in shares)	0	0	4,275,127

Preferred Stock (Narrative) (De

Preferred Stock (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Temporary Equity [Line Items]
Redemption of IPL's cumulative preferred stock	$ 0	$ 200	$ 0
IPL [Member]
Temporary Equity [Line Items]
Redemption of IPL's cumulative preferred stock	$ 0	200	$ 0
IPL [Member] | Cumulative Preferred Stock [Member]
Temporary Equity [Line Items]
Shares outstanding (in shares)			8,000
Cumulative preferred stock rate			5.10%
Preferred stock redemption price per share (in dollars per share)			$ 25
Redemption of IPL's cumulative preferred stock		200
Non-cash charge, preferred stock redemption		$ 5

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Jan. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			$ 1,000
Long-term debt			8,143	$ 7,425
Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			500
IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			100
Long-term debt			3,675	3,675
WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			400
Long-term debt			$ 2,800	$ 2,450
Alliant Energy Finance, LLC [Member] | Term loan credit agreement through January 2024 [Member] | Term Loan Credit Agreement [Member] | Subsequent Event
Debt Instrument [Line Items]
Long-term debt		$ 50
Forecast [Member] | Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500
Forecast [Member] | IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	400
Forecast [Member] | WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500

Debt (Credit Facilities) (Detai

Debt (Credit Facilities) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 642	$ 515
Weighted average interest rates	4.60%	0.20%
Available credit facility capacity	$ 358	$ 485
IPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	0	0
Available credit facility capacity	100	250
WPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 290	$ 236
Weighted average interest rates	4.50%	0.20%
Available credit facility capacity	$ 110	$ 64

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 665	$ 648
Average amount outstanding (based on daily outstanding balances)	$ 411	$ 459
Weighted average interest rates	2.10%	0.20%
IPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 0	$ 19
Average amount outstanding (based on daily outstanding balances)	$ 0	$ 0
Weighted average interest rates	0%	0.20%
WPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 325	$ 320
Average amount outstanding (based on daily outstanding balances)	$ 153	$ 172
Weighted average interest rates	1.60%	0.10%

Debt (Long-term Debt) (Details)

Debt (Long-term Debt) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Mar. 31, 2022
Debt Instrument [Line Items]
Long-term debt	$ 8,143	$ 8,143	$ 7,425
Current maturities	(408)	(408)	(633)
Unamortized debt issuance costs	(45)	(45)	(42)
Unamortized debt (discount) and premium, net	(22)	(22)	(15)
Long-term debt, net	7,668	7,668	6,735
Proceeds from issuance of long-term debt		1,338	600	$ 1,250
Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,675	3,675	3,675
Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500	$ 500
Interest rate	3.25%	3.25%	3.25%
Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	3.40%	3.40%	3.40%
Senior Debentures [Member] | 5.5% senior debenture, due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50	$ 50	$ 50
Interest rate	5.50%	5.50%	5.50%
Senior Debentures [Member] | 4.1% senior debenture, due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500	$ 500
Interest rate	4.10%	4.10%	4.10%
Senior Debentures [Member] | 3.6% senior debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.60%	3.60%	3.60%
Senior Debentures [Member] | 2.3% senior debenture, due 2030 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400	$ 400
Interest rate	2.30%	2.30%	2.30%
Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100	$ 100
Interest rate	6.45%	6.45%	6.45%
Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 125	$ 125	$ 125
Interest rate	6.30%	6.30%	6.30%
Senior Debentures [Member] | 6.25% senior debenture, due 2039 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	6.25%	6.25%	6.25%
Senior Debentures [Member] | 4.7% senior debenture, due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	4.70%	4.70%	4.70%
Senior Debentures [Member] | 3.7% senior debenture, due 2046 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.70%	3.70%	3.70%
Senior Debentures [Member] | 3.5% senior debenture, due 2049 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.50%	3.50%	3.50%
Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.10%	3.10%	3.10%
Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,800	$ 2,800	$ 2,450
Debentures [Member] | 3.05% debenture, due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.05%	3.05%	3.05%
Debentures [Member] | 3% debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350	$ 350
Interest rate	3%	3%	3%
Debentures [Member] | 1.95% debenture, due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	1.95%	1.95%	1.95%
Debentures [Member] | 3.95% debenture, due 2032 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 600	$ 600	$ 0
Interest rate	3.95%	3.95%
Debentures [Member] | 6.25% debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100	$ 100
Interest rate	6.25%	6.25%	6.25%
Debentures [Member] | 6.375% debenture, due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	6.375%	6.375%	6.375%
Debentures [Member] | 7.6% debenture, due 2038 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	7.60%	7.60%	7.60%
Debentures [Member] | 4.1% debenture, due 2044 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	4.10%	4.10%	4.10%
Debentures [Member] | 3.65% debenture, due 2050 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350	$ 350
Interest rate	3.65%	3.65%	3.65%
Debentures [Member] | 2.25% debenture, due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	$ 0	$ 250
Interest rate			2.25%
Other Long Term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	1,668	1,668	$ 1,300
Other [Member] | Other, 1% at December 31, 2022, due 2023 to 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1	$ 1	1
Interest rate	1%	1%
IPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,675	$ 3,675	3,675
Current maturities	0	0	0
Unamortized debt issuance costs	(21)	(21)	(23)
Unamortized debt (discount) and premium, net	(8)	(8)	(9)
Long-term debt, net	3,646	3,646	3,643
Proceeds from issuance of long-term debt		0	300	400
IPL [Member] | Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,675	3,675	3,675
IPL [Member] | Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500	$ 500
Interest rate	3.25%	3.25%	3.25%
IPL [Member] | Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	3.40%	3.40%	3.40%
IPL [Member] | Senior Debentures [Member] | 5.5% senior debenture, due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50	$ 50	$ 50
Interest rate	5.50%	5.50%	5.50%
IPL [Member] | Senior Debentures [Member] | 4.1% senior debenture, due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500	$ 500
Interest rate	4.10%	4.10%	4.10%
IPL [Member] | Senior Debentures [Member] | 3.6% senior debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.60%	3.60%	3.60%
IPL [Member] | Senior Debentures [Member] | 2.3% senior debenture, due 2030 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400	$ 400
Interest rate	2.30%	2.30%	2.30%
IPL [Member] | Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100	$ 100
Interest rate	6.45%	6.45%	6.45%
IPL [Member] | Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 125	$ 125	$ 125
Interest rate	6.30%	6.30%	6.30%
IPL [Member] | Senior Debentures [Member] | 6.25% senior debenture, due 2039 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	6.25%	6.25%	6.25%
IPL [Member] | Senior Debentures [Member] | 4.7% senior debenture, due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	4.70%	4.70%	4.70%
IPL [Member] | Senior Debentures [Member] | 3.7% senior debenture, due 2046 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.70%	3.70%	3.70%
IPL [Member] | Senior Debentures [Member] | 3.5% senior debenture, due 2049 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.50%	3.50%	3.50%
IPL [Member] | Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.10%	3.10%	3.10%
WPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,800	$ 2,800	$ 2,450
Current maturities	0	0	(250)
Unamortized debt issuance costs	(19)	(19)	(15)
Unamortized debt (discount) and premium, net	(11)	(11)	(6)
Long-term debt, net	2,770	2,770	2,179
Proceeds from issuance of long-term debt		588	300	$ 350
WPL [Member] | Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	2,800	2,800	2,450
WPL [Member] | Debentures [Member] | 3.05% debenture, due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	3.05%	3.05%	3.05%
WPL [Member] | Debentures [Member] | 3% debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350	$ 350
Interest rate	3%	3%	3%
WPL [Member] | Debentures [Member] | 1.95% debenture, due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	1.95%	1.95%	1.95%
WPL [Member] | Debentures [Member] | 3.95% debenture, due 2032 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 600	$ 600	$ 0
Interest rate	3.95%	3.95%
WPL [Member] | Debentures [Member] | 6.25% debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100	$ 100
Interest rate	6.25%	6.25%	6.25%
WPL [Member] | Debentures [Member] | 6.375% debenture, due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	6.375%	6.375%	6.375%
WPL [Member] | Debentures [Member] | 7.6% debenture, due 2038 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	7.60%	7.60%	7.60%
WPL [Member] | Debentures [Member] | 4.1% debenture, due 2044 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250	$ 250
Interest rate	4.10%	4.10%	4.10%
WPL [Member] | Debentures [Member] | 3.65% debenture, due 2050 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350	$ 350
Interest rate	3.65%	3.65%	3.65%
WPL [Member] | Debentures [Member] | 2.25% debenture, due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	$ 0	$ 250
Interest rate			2.25%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.75% senior notes, due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400	$ 400
Interest rate	3.75%	3.75%	3.75%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 1.4% senior notes, due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 200	$ 200	$ 200
Interest rate	1.40%	1.40%	1.40%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 4.25% senior notes, due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300	$ 300
Interest rate	4.25%	4.25%	4.25%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.6% senior notes, due 2032 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350	$ 0
Interest rate	3.60%	3.60%
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024, Variable Rate [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400	0		$ 300
Interest rate	5%	5%
Proceeds from issuance of long-term debt	$ 100
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	$ 0	$ 300
Interest rate			1%
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2024, Fixed Rate [Member]
Debt Instrument [Line Items]
Interest rate	3.93%	3.93%
Sheboygan Power, LLC [Member] | Senior Secured Notes [Member] | 5.06% senior secured notes, due 2023 to 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 17	$ 17	$ 24
Interest rate	5.06%	5.06%	5.06%
Corporate Services [Member] | Senior Notes [Member] | 3.45% senior notes, due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 0	$ 0	$ 75
Interest rate			3.45%

Debt (Schedule Of Debt Maturiti

Debt (Schedule Of Debt Maturities) (Details) $ in Millions	Dec. 31, 2022 USD ($)
2023	$ 408
2024	909
2025	300
2026	200
2027	300
IPL [Member]
2023	0
2024	500
2025	300
2026	0
2027	0
WPL [Member]
2023	0
2024	0
2025	0
2026	0
2027	300
Alliant Energy Finance, LLC [Member]
2023	408
2024	409
2025	0
2026	200
2027	$ 0

Leases (Narrative) (Details)

Leases (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) lease_renewal_period_option
Leases [Line Items]
Finance lease liabilities arising from obtaining leased assets	$ 125
WPL [Member]
Leases [Line Items]
Finance lease liabilities arising from obtaining leased assets	$ 125
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance lease, renewal options (in number of renewal periods) | lease_renewal_period_option	2

Leases (Operating Leases) (Deta

Leases (Operating Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 16	$ 14
Operating leases liabilities, Other current liabilities	3	2
Operating leases liabilities, Other liabilities	13	12
Operating leases liabilities, Total	$ 16	$ 14
Operating leases, Weighted average remaining lease term	10 years	9 years
Operating leases, Weighted average discount rate, percent	4%	4%
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other	Other
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other	Other
IPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 9	$ 9
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	8	8
Operating leases liabilities, Total	$ 9	$ 9
Operating leases, Weighted average remaining lease term	11 years	11 years
Operating leases, Weighted average discount rate, percent	4%	4%
WPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 6	$ 5
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	5	4
Operating leases liabilities, Total	$ 6	$ 5
Operating leases, Weighted average remaining lease term	9 years	8 years
Operating leases, Weighted average discount rate, percent	4%	4%

Leases (Finance Lease) (Details

Leases (Finance Lease) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 133	$ 11
Finance lease liabilities, Other current liabilities	5	1
Finance lease liabilities, Other liabilities	131	11
Finance lease liabilities, Total	$ 136	$ 12
Finance lease, Remaining lease term	34 years	34 years
Finance lease, Discount rate, percent	5%	3%
Finance lease, Depreciation expense	$ 0	$ 0	$ 0
Finance lease, Interest expense	3	0	0
Finance lease, Total expense	$ 3	$ 0	0
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 133	$ 11
Finance lease liabilities, Other current liabilities	5	1
Finance lease liabilities, Other liabilities	$ 131	$ 11
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant and equipment, net	Property, plant and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
WPL [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 148	$ 32
Finance lease liabilities, Other current liabilities	17	11
Finance lease liabilities, Other liabilities	150	42
Finance lease liabilities, Total	$ 167	$ 53
Finance lease, Remaining lease term	28 years	10 years
Finance lease, Discount rate, percent	5%	9%
Finance lease, Depreciation expense	$ 6	$ 6	6
Finance lease, Interest expense	7	5	6
Finance lease, Total expense	13	11	$ 12
WPL [Member] | Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	15	21
Finance lease liabilities, Other current liabilities	12	10
Finance lease liabilities, Other liabilities	19	31
WPL [Member] | Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	133	11
Finance lease liabilities, Other current liabilities	5	1
Finance lease liabilities, Other liabilities	$ 131	$ 11

Leases (Expected Maturities of

Leases (Expected Maturities of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Leases [Line Items]
Operating Leases Liability, 2023	$ 3
Operating Leases Liability, 2024	2
Operating Leases Liability, 2025	2
Operating Leases Liability, 2026	2
Operating Leases Liability, 2027	2
Operating Leases Liability, Thereafter	9
Operating Leases Liability, Total	20
Operating Leases Liability, Less: amount representing interest	4
Operating Leases Liability, Present value of minimum lease payments	16	$ 14
Finance Lease Liability, 2023	5
Finance Lease Liability, 2024	6
Finance Lease Liability, 2025	6
Finance Lease Liability, 2026	6
Finance Lease Liability, 2027	6
Finance Lease Liability, Thereafter	262
Finance Lease Liability, Total	291
Finance Lease Liability, Less: amount representing interest	155
Finance Lease Liability, Present value of minimum lease payments	136	12
IPL [Member]
Leases [Line Items]
Operating Leases Liability, 2023	1
Operating Leases Liability, 2024	1
Operating Leases Liability, 2025	1
Operating Leases Liability, 2026	1
Operating Leases Liability, 2027	1
Operating Leases Liability, Thereafter	6
Operating Leases Liability, Total	11
Operating Leases Liability, Less: amount representing interest	2
Operating Leases Liability, Present value of minimum lease payments	9	9
WPL [Member]
Leases [Line Items]
Operating Leases Liability, 2023	1
Operating Leases Liability, 2024	1
Operating Leases Liability, 2025	1
Operating Leases Liability, 2026	1
Operating Leases Liability, 2027	1
Operating Leases Liability, Thereafter	2
Operating Leases Liability, Total	7
Operating Leases Liability, Less: amount representing interest	1
Operating Leases Liability, Present value of minimum lease payments	6	5
Finance Lease Liability, 2023	20
Finance Lease Liability, 2024	21
Finance Lease Liability, 2025	12
Finance Lease Liability, 2026	6
Finance Lease Liability, 2027	6
Finance Lease Liability, Thereafter	262
Finance Lease Liability, Total	327
Finance Lease Liability, Less: amount representing interest	160
Finance Lease Liability, Present value of minimum lease payments	$ 167	$ 53

Disaggregation of Revenues (Det

Disaggregation of Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 4,205	$ 3,669	$ 3,416
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,256	2,063	1,947
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,856	1,523	1,395
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,421	3,081	2,920
Electric [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,859	1,752	1,695
Electric [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,562	1,329	1,225
Electric [Member] | Retail - Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,233	1,115	1,093
Electric [Member] | Retail - Residential [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	673	620	602
Electric [Member] | Retail - Residential [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	560	495	491
Electric [Member] | Retail - Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues	821	763	718
Electric [Member] | Retail - Commercial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	536	508	474
Electric [Member] | Retail - Commercial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	285	255	244
Electric [Member] | Retail - Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	965	893	841
Electric [Member] | Retail - Industrial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	538	505	488
Electric [Member] | Retail - Industrial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	427	388	353
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenues	233	187	168
Electric [Member] | Wholesale [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	64	57	57
Electric [Member] | Wholesale [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	169	130	111
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	169	123	100
Electric [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	48	62	74
Electric [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	121	61	26
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues	642	456	373
Gas [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	351	265	208
Gas [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	291	191	165
Gas [Member] | Retail - Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	371	257	214
Gas [Member] | Retail - Residential [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	202	146	116
Gas [Member] | Retail - Residential [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	169	111	98
Gas [Member] | Retail - Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues	197	139	107
Gas [Member] | Retail - Commercial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	101	79	59
Gas [Member] | Retail - Commercial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	96	60	48
Gas [Member] | Retail - Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	20	17	12
Gas [Member] | Retail - Industrial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	14	12	8
Gas [Member] | Retail - Industrial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	6	5	4
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	54	43	40
Gas [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	34	28	25
Gas [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	20	15	15
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenues	49	49	49
Other Utility [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	46	46	44
Other Utility [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	3	3	5
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	10	13	13
Other Utility [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	7	10	8
Other Utility [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	3	3	5
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenues	39	36	36
Other Utility [Member] | Steam [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	39	36	36
Non-Utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	93	83	74
Non-Utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 93	$ 83	$ 74

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax [Line Items]
Overall income tax rate			3%	(12.00%)	(10.00%)
State income tax rate, percent			3%	2%	2%
Reduction of tax-related regulatory assets			$ (108)	$ 51	$ (130)
Income tax expense (benefit)			22	$ (74)	$ (57)
Tax-related [Member]
Income Tax [Line Items]
Reduction of tax-related regulatory assets			77
Income tax expense (benefit)			$ 8
IPL [Member]
Income Tax [Line Items]
Overall income tax rate			(16.00%)	(11.00%)	(16.00%)
State income tax rate, percent			(2.00%)	(1.00%)	(1.00%)
Reduction of tax-related regulatory assets			$ 56	$ 30	$ (93)
Income tax expense (benefit)			(50)	$ (36)	$ (47)
IPL [Member] | Tax-related [Member]
Income Tax [Line Items]
Reduction of tax-related regulatory assets			$ 77
WPL [Member]
Income Tax [Line Items]
Overall income tax rate			17%	(24.00%)	(8.00%)
State income tax rate, percent			6%	6%	6%
Reduction of tax-related regulatory assets			$ (163)	$ 21	$ (37)
Income tax expense (benefit)			$ 66	$ (51)	$ (19)
State [Member]
Income Tax [Line Items]
Overall income tax rate				9.80%	12%
State [Member] | Forecast [Member]
Income Tax [Line Items]
State income tax rate, percent	5.50%	8.40%

Income Taxes (Schedule Of Compo

Income Taxes (Schedule Of Components Of Income Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current tax expense (benefit):
Federal	$ 7	$ 1	$ 1
State	2	3	8
Deferred tax expense (benefit):
Federal	109	9	22
State	28	15	8
Production tax credits	(123)	(101)	(95)
Investment tax credits	(1)	(1)	(1)
Income tax expense (benefit)	22	(74)	(57)
IPL [Member]
Current tax expense (benefit):
Federal	(29)	(21)	6
State	(8)	(1)	(1)
Deferred tax expense (benefit):
Federal	91	73	30
State	1	0	(2)
Production tax credits	(105)	(87)	(80)
Investment tax credits	0	0	0
Income tax expense (benefit)	(50)	(36)	(47)
WPL [Member]
Current tax expense (benefit):
Federal	46	22	(11)
State	16	6	7
Deferred tax expense (benefit):
Federal	10	(75)	(9)
State	12	11	10
Production tax credits	(18)	(14)	(15)
Investment tax credits	0	(1)	(1)
Income tax expense (benefit)	$ 66	$ (51)	$ (19)

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21%	21%	21%
State income taxes, net of federal benefits	3%	2%	2%
Production tax credits	(18.00%)	(17.00%)	(17.00%)
Amortization of excess deferred taxes	(2.00%)	(18.00%)	(13.00%)
Effect of rate-making on property-related differences	(1.00%)	(1.00%)	(3.00%)
Adjustment for prior period taxes	1%	1%	1%
Other items, net	(1.00%)	0%	(1.00%)
Overall income tax rate	3%	(12.00%)	(10.00%)
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21%	21%	21%
State income taxes, net of federal benefits	(2.00%)	(1.00%)	(1.00%)
Production tax credits	(34.00%)	(27.00%)	(28.00%)
Amortization of excess deferred taxes	(2.00%)	(4.00%)	(5.00%)
Effect of rate-making on property-related differences	(1.00%)	(2.00%)	(4.00%)
Adjustment for prior period taxes	1%	2%	1%
Other items, net	1%	0%	0%
Overall income tax rate	(16.00%)	(11.00%)	(16.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21%	21%	21%
State income taxes, net of federal benefits	6%	6%	6%
Production tax credits	(5.00%)	(6.00%)	(7.00%)
Amortization of excess deferred taxes	(3.00%)	(43.00%)	(26.00%)
Effect of rate-making on property-related differences	(2.00%)	(1.00%)	(2.00%)
Adjustment for prior period taxes	0%	0%	0%
Other items, net	0%	(1.00%)	0%
Overall income tax rate	17%	(24.00%)	(8.00%)

Income Taxes (Schedule Of Defer

Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax liabilities, property	$ 2,442	$ 2,389
Deferred tax liabilities, other	155	111
Total deferred tax liabilities	2,722	2,623
Deferred tax assets, federal credit carryforwards	672	560
Deferred tax assets, net operating losses carryforwards - federal	0	39
Deferred tax assets, net operating losses carryforwards - state	32	38
Deferred tax assets, other	75	65
Subtotal deferred tax assets	779	702
Deferred tax assets, valuation allowances	0	(6)
Total deferred tax assets	779	696
Total deferred tax liabilities, net	1,943	1,927
IPL [Member]
Deferred tax liabilities, property	1,440	1,416
Deferred tax liabilities, other	86	76
Total deferred tax liabilities	1,526	1,492
Deferred tax assets, federal credit carryforwards	450	345
Deferred tax assets, net operating losses carryforwards - federal	0	36
Deferred tax assets, net operating losses carryforwards - state	0	3
Deferred tax assets, other	29	25
Subtotal deferred tax assets	479	409
Deferred tax assets, valuation allowances	0	0
Total deferred tax assets	479	409
Total deferred tax liabilities, net	1,047	1,083
WPL [Member]
Deferred tax liabilities, property	938	913
Deferred tax liabilities, other	80	50
Total deferred tax liabilities	1,018	963
Deferred tax assets, federal credit carryforwards	209	192
Deferred tax assets, net operating losses carryforwards - federal	0	0
Deferred tax assets, net operating losses carryforwards - state	0	0
Deferred tax assets, other	20	18
Subtotal deferred tax assets	229	210
Deferred tax assets, valuation allowances	0	0
Total deferred tax assets	229	210
Total deferred tax liabilities, net	789	753
ATC Holdings [Member]
Deferred tax liabilities, ATC Holdings	125	123
ATC Holdings [Member] | IPL [Member]
Deferred tax liabilities, ATC Holdings	0	0
ATC Holdings [Member] | WPL [Member]
Deferred tax liabilities, ATC Holdings	$ 0	$ 0

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2022 USD ($)
State [Member]
Tax carryforwards, net operating losses	$ 527
State [Member] | IPL [Member]
Tax carryforwards, net operating losses	10
State [Member] | WPL [Member]
Tax carryforwards, net operating losses	1
Federal [Member]
Tax carryforwards, tax credits	672
Federal [Member] | IPL [Member]
Tax carryforwards, tax credits	450
Federal [Member] | WPL [Member]
Tax carryforwards, tax credits	$ 209

Income Taxes (Schedule Of Uncer

Income Taxes (Schedule Of Uncertain Tax Positions) (Details)	12 Months Ended
	Dec. 31, 2022
Statute of limitations, expiration period from extended due date of federal tax return	3 years
Statute of limitations, expiration period from extended due date of Iowa tax return	3 years
Statute of limitations, expiration period from extended due date of Wisconsin tax return	4 years

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Benefit Plans [Line Items]
Total plan assets (less than 1%), percentage of common stock	1%	1%
Common stock percentage in assets held in 401(k) saving plans	10%	9%
Unrecognized compensation cost	$ 6
Percentage of base salary and short-term cash incentive compensation	100%
Carrying value of deferred compensation obligations	$ 19	$ 22
Performance Shares Equity Awards [Member]
Benefit Plans [Line Items]
Performance period	3 years
Restricted Stock Units Equity Awards [Member]
Benefit Plans [Line Items]
Performance period	3 years
Instrument valuation based on shares of common stock, number of shares	1
Performance Restricted Stock Units Equity Awards [Member]
Benefit Plans [Line Items]
Performance period	3 years
Instrument valuation based on shares of common stock, number of shares	1
Minimum [Member]
Benefit Plans [Line Items]
Unrecognized compensation cost recognized over a weighted average period	1 year
Minimum [Member] | Performance Shares Equity Awards [Member]
Benefit Plans [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0%
Minimum [Member] | Performance Restricted Stock Units Equity Awards [Member]
Benefit Plans [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0%
Maximum [Member]
Benefit Plans [Line Items]
Unrecognized compensation cost recognized over a weighted average period	2 years
Maximum [Member] | Performance Shares Equity Awards [Member]
Benefit Plans [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200%
Maximum [Member] | Performance Restricted Stock Units Equity Awards [Member]
Benefit Plans [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200%
IPL [Member]
Benefit Plans [Line Items]
Unrecognized compensation cost	$ 3
WPL [Member]
Benefit Plans [Line Items]
Unrecognized compensation cost	2
Other Postretirement Benefits Plans [Member]
Benefit Plans [Line Items]
Plan asset threshold for long-term allocation targets	5
Other Postretirement Benefits Plans [Member] | IPL [Member]
Benefit Plans [Line Items]
Plan asset threshold for long-term allocation targets	5
Other Postretirement Benefits Plans [Member] | WPL [Member]
Benefit Plans [Line Items]
Plan asset threshold for long-term allocation targets	$ 5
Omnibus Incentive Plan [Member]
Benefit Plans [Line Items]
Shares available for issuance under the Amended and Restated OIP (in shares)	8,000,000
Shares included in diluted earnings per share (in shares)	320,084

Benefit Plans (Assumptions Used

Benefit Plans (Assumptions Used To Measure Benefit Plans) (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.54%	2.91%	2.57%
Discount rate for net periodic cost	2.91%	2.57%	3.48%
Expected rate of return on plan assets	7.80%	7.10%	7.10%
Interest crediting rate for Alliant Energy Cash Balance Pension Plan	9.22%	4.18%	4.76%
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.55%	2.94%	2.61%
Discount rate for net periodic cost	2.94%	2.61%	3.51%
Expected rate of return on plan assets	7.80%	7.10%	7.10%
Rate of compensation increase	3.30%	3.30%	3.65%
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.54%	2.94%	2.64%
Discount rate for net periodic cost	2.94%	2.64%	3.50%
Expected rate of return on plan assets	7.80%	7.10%	7.10%
Rate of compensation increase	3.30%	3.30%	3.65%
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.53%	2.81%	2.31%
Discount rate for net periodic cost	2.81%	2.31%	3.40%
Expected rate of return on plan assets	6.40%	4.80%	4.50%
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.53%	2.80%	2.28%
Discount rate for net periodic cost	2.80%	2.28%	3.39%
Expected rate of return on plan assets	6.50%	5.10%	4.50%
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	5.53%	2.79%	2.27%
Discount rate for net periodic cost	2.79%	2.27%	3.39%
Expected rate of return on plan assets	5.49%	4.02%	3.28%
Minimum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.30%	3.30%	3.65%
Maximum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	4.50%	4.50%	4.50%

Benefit Plans (Defined Benefit

Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension settlement losses	$ (6)	$ (5)	$ (14)
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	11	11
Interest cost	36	34	43
Expected return on plan assets	(69)	(69)	(70)
Amortization of prior service cost (credit)	(1)	0	0
Amortization of actuarial loss	32	39	34
Settlement losses	26	0	12
Total	33	15	30
Pension settlement losses	7
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	4	3
Interest cost	6	5	7
Expected return on plan assets	(5)	(5)	(5)
Amortization of prior service cost (credit)	0	0	0
Amortization of actuarial loss	2	5	3
Settlement losses	0	0	0
Total	6	9	8
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension settlement losses	(6)	(1)	(8)
IPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	7	7
Interest cost	16	16	20
Expected return on plan assets	(31)	(32)	(33)
Amortization of actuarial loss	13	17	15
Settlement losses	13	0	7
Total	17	8	16
Pension settlement losses	7
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1
Interest cost	2	2	3
Expected return on plan assets	(4)	(3)	(4)
Amortization of actuarial loss	1	2	1
Settlement losses	0	0	0
Total	0	2	1
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension settlement losses	1	(2)	(3)
WPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	4	4
Interest cost	16	15	19
Expected return on plan assets	(31)	(31)	(31)
Amortization of prior service cost (credit)	0	0	0
Amortization of actuarial loss	15	19	16
Settlement losses	13	0	0
Total	16	7	8
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2
Interest cost	2	2	3
Expected return on plan assets	(1)	0	(1)
Amortization of prior service cost (credit)	0	0	(1)
Amortization of actuarial loss	2	2	2
Settlement losses	0	0	0
Total	$ 4	$ 5	$ 5

Benefit Plans (Funded Status of

Benefit Plans (Funded Status of Benefits Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	$ 875	$ 1,251
Change in benefit obligation:
Net benefit obligation at January 1	1,251	1,351
Service cost	9	11	$ 11
Interest cost	36	34	43
Plan participants' contributions	0	0
Actuarial (gain) loss	(269)	(46)
Gross benefits paid	(152)	(99)
Net benefit obligation at December 31	875	1,251	1,351
Change in plan assets:
Fair value of plan assets at January 1	1,011	984
Actual return on plan assets	(204)	87
Employer contributions	51	39
Plan participants' contributions	0	0
Gross benefits paid	(152)	(99)
Fair value of plan assets at December 31	706	1,011	984
Under funded status at December 31	(169)	(240)
Fair value of plan assets	706	1,011
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	389	567
Change in benefit obligation:
Net benefit obligation at January 1	567	615
Service cost	6	7	7
Interest cost	16	16	20
Plan participants' contributions	0	0
Actuarial (gain) loss	(123)	(23)
Gross benefits paid	(77)	(48)
Net benefit obligation at December 31	389	567	615
Change in plan assets:
Fair value of plan assets at January 1	462	453
Actual return on plan assets	(92)	40
Employer contributions	51	17
Plan participants' contributions	0	0
Gross benefits paid	(77)	(48)
Fair value of plan assets at December 31	344	462	453
Under funded status at December 31	(45)	(105)
Fair value of plan assets	344	462
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	381	546
Change in benefit obligation:
Net benefit obligation at January 1	546	588
Service cost	3	4	4
Interest cost	16	15	19
Plan participants' contributions	0	0
Actuarial (gain) loss	(117)	(18)
Gross benefits paid	(67)	(43)
Net benefit obligation at December 31	381	546	588
Change in plan assets:
Fair value of plan assets at January 1	450	436
Actual return on plan assets	(92)	39
Employer contributions	0	18
Plan participants' contributions	0	0
Gross benefits paid	(67)	(43)
Fair value of plan assets at December 31	291	450	436
Under funded status at December 31	(90)	(96)
Fair value of plan assets	291	450
Other Postretirement Benefits Plans [Member]
Change in benefit obligation:
Net benefit obligation at January 1	210	227
Service cost	3	4	3
Interest cost	6	5	7
Plan participants' contributions	4	5
Actuarial (gain) loss	(37)	(12)
Gross benefits paid	(18)	(19)
Net benefit obligation at December 31	168	210	227
Change in plan assets:
Fair value of plan assets at January 1	106	108
Actual return on plan assets	(17)	4
Employer contributions	8	8
Plan participants' contributions	4	5
Gross benefits paid	(18)	(19)
Fair value of plan assets at December 31	83	106	108
Under funded status at December 31	(85)	(104)
Other Postretirement Benefits Plans [Member] | IPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	84	91
Service cost	1	1	1
Interest cost	2	2	3
Plan participants' contributions	2	2
Actuarial (gain) loss	(14)	(4)
Gross benefits paid	(7)	(8)
Net benefit obligation at December 31	68	84	91
Change in plan assets:
Fair value of plan assets at January 1	74	74
Actual return on plan assets	(12)	4
Employer contributions	1	2
Plan participants' contributions	2	2
Gross benefits paid	(7)	(8)
Fair value of plan assets at December 31	58	74	74
Under funded status at December 31	(10)	(10)
Other Postretirement Benefits Plans [Member] | WPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	81	89
Service cost	1	1	2
Interest cost	2	2	3
Plan participants' contributions	2	2
Actuarial (gain) loss	(13)	(5)
Gross benefits paid	(8)	(8)
Net benefit obligation at December 31	65	81	89
Change in plan assets:
Fair value of plan assets at January 1	17	18
Actual return on plan assets	(2)	0
Employer contributions	5	5
Plan participants' contributions	2	2
Gross benefits paid	(8)	(8)
Fair value of plan assets at December 31	14	17	$ 18
Under funded status at December 31	$ (51)	$ (64)

Benefit Plans (Amounts Recogniz

Benefit Plans (Amounts Recognized On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	$ (277)	$ (374)
Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	(2)	(2)
Pension and other benefit obligations	(167)	(238)
Net amounts recognized at December 31	(169)	(240)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	376	429
Prior service credit	(3)	(4)
Net amount recognized at December 31	373	425
Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	9	13
Current liabilities	(8)	(8)
Pension and other benefit obligations	(86)	(109)
Net amounts recognized at December 31	(85)	(104)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	20	38
Prior service credit	0	(1)
Net amount recognized at December 31	20	37
IPL [Member]
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	(62)	(127)
IPL [Member] | Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	0	0
Pension and other benefit obligations	(45)	(105)
Net amounts recognized at December 31	(45)	(105)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	154	180
Prior service credit	(1)	(1)
Net amount recognized at December 31	153	179
IPL [Member] | Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	6	10
Current liabilities	(2)	(2)
Pension and other benefit obligations	(14)	(18)
Net amounts recognized at December 31	(10)	(10)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	14	13
Prior service credit	0	0
Net amount recognized at December 31	14	13
WPL [Member]
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	(140)	(159)
WPL [Member] | Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	0	0
Pension and other benefit obligations	(90)	(96)
Net amounts recognized at December 31	(90)	(96)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	165	188
Prior service credit	0	(1)
Net amount recognized at December 31	165	187
WPL [Member] | Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	3	3
Current liabilities	(5)	(6)
Pension and other benefit obligations	(49)	(61)
Net amounts recognized at December 31	(51)	(64)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	6	18
Prior service credit	0	(1)
Net amount recognized at December 31	$ 6	$ 17

Benefit Plans (Accumulated Bene

Benefit Plans (Accumulated Benefit Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	$ 857	$ 1,214
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	857	1,214
Fair value of plan assets	706	1,011
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	875	1,251
Fair value of plan assets	706	1,011
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	168	210
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	168	210
Fair value of plan assets	83	106
IPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	379	546
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	379	546
Fair value of plan assets	344	462
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	389	567
Fair value of plan assets	344	462
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	68	84
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	68	84
Fair value of plan assets	58	74
WPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	373	532
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	373	532
Fair value of plan assets	291	450
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	381	546
Fair value of plan assets	291	450
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	65	81
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	65	81
Fair value of plan assets	$ 14	$ 17

Benefit Plans (Regulatory Asset

Benefit Plans (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 30	$ 35
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 25	$ 30

Benefit Plans (Estimated Future

Benefit Plans (Estimated Future Funding) (Details) - Forecast [Member] $ in Millions	Dec. 31, 2023 USD ($)
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2023	$ 12
Defined Benefit Pension Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2023	1
Defined Benefit Pension Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2023	10
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2023	8
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2023	2
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2023	$ 6

Benefit Plans (Expected Benefit

Benefit Plans (Expected Benefit Payments) (Details) $ in Millions	Dec. 31, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	$ 90
Expected benefit payments, 2024	89
Expected benefit payments, 2025	90
Expected benefit payments, 2026	91
Expected benefit payments, 2027	90
Expected benefit payments, 2028 - 2032	418
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	72
Expected benefit payments, 2024	71
Expected benefit payments, 2025	72
Expected benefit payments, 2026	74
Expected benefit payments, 2027	74
Expected benefit payments, 2028 - 2032	349
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	18
Expected benefit payments, 2024	18
Expected benefit payments, 2025	18
Expected benefit payments, 2026	17
Expected benefit payments, 2027	16
Expected benefit payments, 2028 - 2032	69
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	41
Expected benefit payments, 2024	40
Expected benefit payments, 2025	41
Expected benefit payments, 2026	40
Expected benefit payments, 2027	39
Expected benefit payments, 2028 - 2032	182
IPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	34
Expected benefit payments, 2024	33
Expected benefit payments, 2025	34
Expected benefit payments, 2026	33
Expected benefit payments, 2027	32
Expected benefit payments, 2028 - 2032	155
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	7
Expected benefit payments, 2024	7
Expected benefit payments, 2025	7
Expected benefit payments, 2026	7
Expected benefit payments, 2027	7
Expected benefit payments, 2028 - 2032	27
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	39
Expected benefit payments, 2024	38
Expected benefit payments, 2025	38
Expected benefit payments, 2026	38
Expected benefit payments, 2027	37
Expected benefit payments, 2028 - 2032	174
WPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	32
Expected benefit payments, 2024	31
Expected benefit payments, 2025	31
Expected benefit payments, 2026	31
Expected benefit payments, 2027	31
Expected benefit payments, 2028 - 2032	148
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2023	7
Expected benefit payments, 2024	7
Expected benefit payments, 2025	7
Expected benefit payments, 2026	7
Expected benefit payments, 2027	6
Expected benefit payments, 2028 - 2032	$ 26

Benefit Plans (Allocation Of Pl

Benefit Plans (Allocation Of Plan Assets) (Details)	Dec. 31, 2022
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	4%
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	33%
Pension Plans, Defined Benefit [Member] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	21%
Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	5%
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	37%
Other Postretirement Benefits Plans [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	1%
Other Postretirement Benefits Plans [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	35%
Other Postretirement Benefits Plans [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	64%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	0%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	14%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	11%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	2%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	27%
Minimum [Member] | Other Postretirement Benefits Plans [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	0%
Minimum [Member] | Other Postretirement Benefits Plans [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	0%
Minimum [Member] | Other Postretirement Benefits Plans [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	40%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	5%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	61%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	31%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	11%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	47%
Maximum [Member] | Other Postretirement Benefits Plans [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	5%
Maximum [Member] | Other Postretirement Benefits Plans [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	55%
Maximum [Member] | Other Postretirement Benefits Plans [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	100%

Benefit Plans (Fair Value Of Pl

Benefit Plans (Fair Value Of Plan Assets By Asset Category And Fair Value Hierarchy Level) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 706	$ 1,011	$ 984
Assets measured at net asset value	276	477
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79	35
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79	35
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	185	256
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	185	256
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	52
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	52
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	130	191
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30	47
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	100	144
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in fair value hierarchy	429	534
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	250	355
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	179	179
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Accrued investment income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	344	462	453
Assets measured at net asset value	124	218
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62	16
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62	16
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	117
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	117
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	24
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	24
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	58	87
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	21
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45	66
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in fair value hierarchy	219	244
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	112	162
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	107	82
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | IPL [Member] | Accrued investment income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	291	450	436
Assets measured at net asset value	122	212
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	16
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	16
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82	114
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82	114
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	23
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	23
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	57	85
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	21
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44	64
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Total assets in fair value hierarchy	168	238
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	111	158
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	57	80
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | WPL [Member] | Accrued investment income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	106	108
Assets measured at net asset value	23	29
Total assets in fair value hierarchy	60	77
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	56	70
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	7
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	11
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	11
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47	60
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46	58
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	2
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	58	74	74
Assets measured at net asset value	18	23
Total assets in fair value hierarchy	40	51
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	39	50
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	8
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	8
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34	42
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34	42
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	17	$ 18
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	16
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	15
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	15
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ (1)

Benefit Plans (Employees Partic

Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
401(k) costs	$ 28	$ 26	$ 25
IPL [Member]
401(k) costs	13	13	13
WPL [Member]
401(k) costs	$ 13	$ 12	$ 12

Benefit Plans (Recognized Compe

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Compensation expense	$ 13	$ 14	$ 16
Income tax benefits	3	4	4
IPL [Member]
Compensation expense	7	8	9
Income tax benefits	2	2	2
WPL [Member]
Compensation expense	5	6	6
Income tax benefits	$ 1	$ 2	$ 2

Benefit Plans (Summary Of Perfo

Benefit Plans (Summary Of Performance Shares Activity) (Details) - Performance Shares Equity Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	196,429	129,156	74,193
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 51.59	$ 54.63	$ 47.44
Granted (in shares/awards)	74,106	73,112	56,204
Granted, weighted average grant date fair value (in dollars per share)	$ 54.45	$ 46.19	$ 64.04
Vested (in shares/awards)	(71,101)	0	0
Vested, weighted average grant date fair value (in dollars per share)	$ 47.48	$ 0	$ 0
Forfeited (in shares/awards)	(9,161)	(5,839)	(1,241)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 53.99	$ 51.07	$ 50.94
Nonvested, December 31 (in shares/awards)	190,273	196,429	129,156
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 54.13	$ 51.59	$ 54.63

Benefit Plans (Summary of Restr

Benefit Plans (Summary of Restricted Stock Units) (Details) - Restricted Stock Units Equity Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	217,819	146,549	89,281
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 50.54	$ 51.54	$ 46.04
Granted (in shares/awards)	77,122	80,152	61,056
Granted, weighted average grant date fair value (in dollars per share)	$ 56.88	$ 48.65	$ 59.42
Vested (in shares/awards)	(82,770)	0	0
Vested, weighted average grant date fair value (in dollars per share)	$ 46.08	$ 0	$ 0
Forfeited (in shares/awards)	(13,896)	(8,882)	(3,788)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 55.53	$ 49.84	$ 49.01
Nonvested, December 31 (in shares/awards)	198,275	217,819	146,549
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 54.53	$ 50.54	$ 51.54

Benefit Plans (Summary of Per_2

Benefit Plans (Summary of Performance Restricted Stock Units) (Details) - Performance Restricted Stock Units Equity Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	196,429	197,463	206,065
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 50.74	$ 47.31	$ 41.50
Granted (in shares/awards)	84,670	73,112	56,204
Granted, weighted average grant date fair value (in dollars per share)	$ 57.01	$ 48.66	$ 59.37
Vested (in shares/awards)	(71,101)	(68,307)	(63,565)
Vested, weighted average grant date fair value (in dollars per share)	$ 46.24	$ 38.60	$ 39.12
Forfeited (in shares/awards)	(10,124)	(5,839)	(1,241)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 55.92	$ 50.46	$ 49.25
Nonvested, December 31 (in shares/awards)	199,874	196,429	197,463
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 54.74	$ 50.74	$ 47.31

Benefit Plans (Carrying Value A

Benefit Plans (Carrying Value And Fair Market Value Of The Deferred Compensation Obligation for Company Stock Account) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Carrying value of deferred compensation obligation	$ 13	$ 12
Fair market value of deferred compensation obligation	$ 22	$ 24

Asset Retirement Obligations (R

Asset Retirement Obligations (Reconciliation Of Changes In Asset Retirement Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	$ 294	$ 251
Revisions in estimated cash flows	19	50
Liabilities settled	(48)	(17)
Liabilities incurred	6	3
Accretion expense	8	7
Balance, December 31	279	294
IPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	213	177
Revisions in estimated cash flows	15	44
Liabilities settled	(39)	(13)
Liabilities incurred	0	0
Accretion expense	6	5
Balance, December 31	195	213
WPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	81	74
Revisions in estimated cash flows	4	6
Liabilities settled	(9)	(4)
Liabilities incurred	6	3
Accretion expense	2	2
Balance, December 31	$ 84	$ 81

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] T in Thousands, MWh in Thousands, Dekatherms in Thousands	12 Months Ended
	Dec. 31, 2022 Dekatherms MWh T
Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	1,132
Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	589
Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	543
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	9,046
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	3,999
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs)	5,047
Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	224,060
Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	115,237
Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	108,823
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	781
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	396
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	385

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 111	$ 113
Non-current derivative assets	126	63
Current derivative liabilities	59	8
Non-current derivative liabilities	20	1
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	69	48
Non-current derivative assets	69	36
Current derivative liabilities	40	4
Non-current derivative liabilities	6	0
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	42	65
Non-current derivative assets	57	27
Current derivative liabilities	19	4
Non-current derivative liabilities	$ 14	$ 1

Derivative Instruments (Balance

Derivative Instruments (Balance Sheet Offsetting) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Derivative assets, Gross (as reported)	$ 237	$ 176
Derivative assets, net	193	171
Derivative liabilities, gross (as reported)	79	9
Derivative liabilities, net	35	4
IPL [Member]
Derivative [Line Items]
Derivative assets, Gross (as reported)	138	84
Derivative assets, net	108	83
Derivative liabilities, gross (as reported)	46	4
Derivative liabilities, net	16	3
WPL [Member]
Derivative [Line Items]
Derivative assets, Gross (as reported)	99	92
Derivative assets, net	85	88
Derivative liabilities, gross (as reported)	33	5
Derivative liabilities, net	$ 19	$ 1

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Assets:
Money market fund investments	$ 10	$ 32
Deferred proceeds	185	214
Liabilities and equity:
Long-term debt (including current maturities)	7,339	8,330
Commodity Contracts [Member]
Assets:
Derivatives	237	176
Liabilities and equity:
Derivatives	79	9
Level 1 [Member]
Assets:
Money market fund investments	10	32
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	0	0
Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities and equity:
Derivatives	0	0
Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	7,338	8,329
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	206	146
Liabilities and equity:
Derivatives	67	8
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	185	214
Liabilities and equity:
Long-term debt (including current maturities)	1	1
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	31	30
Liabilities and equity:
Derivatives	12	1
Carrying Amount [Member]
Assets:
Money market fund investments	10	32
Deferred proceeds	185	214
Liabilities and equity:
Long-term debt (including current maturities)	8,076	7,368
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	237	176
Liabilities and equity:
Derivatives	79	9
IPL [Member]
Assets:
Money market fund investments	10	32
Deferred proceeds	185	214
Liabilities and equity:
Long-term debt (including current maturities)	3,228	4,124
IPL [Member] | Commodity Contracts [Member]
Assets:
Derivatives	138	84
Liabilities and equity:
Derivatives	46	4
IPL [Member] | Level 1 [Member]
Assets:
Money market fund investments	10	32
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	0	0
IPL [Member] | Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities and equity:
Derivatives	0	0
IPL [Member] | Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities and equity:
Long-term debt (including current maturities)	3,228	4,124
IPL [Member] | Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	111	65
Liabilities and equity:
Derivatives	35	3
IPL [Member] | Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	185	214
Liabilities and equity:
Long-term debt (including current maturities)	0	0
IPL [Member] | Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	27	19
Liabilities and equity:
Derivatives	11	1
IPL [Member] | Carrying Amount [Member]
Assets:
Money market fund investments	10	32
Deferred proceeds	185	214
Liabilities and equity:
Long-term debt (including current maturities)	3,646	3,643
IPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	138	84
Liabilities and equity:
Derivatives	46	4
WPL [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,542	2,862
WPL [Member] | Commodity Contracts [Member]
Assets:
Derivatives	99	92
Liabilities and equity:
Derivatives	33	5
WPL [Member] | Level 1 [Member]
Liabilities and equity:
Long-term debt (including current maturities)	0	0
WPL [Member] | Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	0	0
Liabilities and equity:
Derivatives	0	0
WPL [Member] | Level 2 [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,542	2,862
WPL [Member] | Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	95	81
Liabilities and equity:
Derivatives	32	5
WPL [Member] | Level 3 [Member]
Liabilities and equity:
Long-term debt (including current maturities)	0	0
WPL [Member] | Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	4	11
Liabilities and equity:
Derivatives	1	0
WPL [Member] | Carrying Amount [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,770	2,429
WPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	99	92
Liabilities and equity:
Derivatives	$ 33	$ 5

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Commodity Contracts Derivative Assets and (Liabilities), net [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, January 1	$ 29	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	(18)	6
Purchases	79	21
Sales	(2)	(1)
Settlements	(69)	(26)
Ending balance, December 31	19	29
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	(18)	6
Commodity Contracts Derivative Assets and (Liabilities), net [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, January 1	18	26
Total net gains (losses) included in changes in net assets (realized/unrealized)	(12)	(3)
Purchases	58	16
Sales	(1)	(1)
Settlements	(47)	(20)
Ending balance, December 31	16	18
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	(13)	(3)
Commodity Contracts Derivative Assets and (Liabilities), net [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, January 1	11	3
Total net gains (losses) included in changes in net assets (realized/unrealized)	(6)	9
Purchases	21	5
Sales	(1)	0
Settlements	(22)	(6)
Ending balance, December 31	3	11
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	(5)	9
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, January 1	214	188
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Purchases	0	0
Sales	0	0
Settlements	(29)	26
Ending balance, December 31	185	214
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	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, January 1	214	188
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Purchases	0	0
Sales	0	0
Settlements	(29)	26
Ending balance, December 31	185	214
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$ 0	$ 0

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	$ 19	$ 29	$ 29
Excluding FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative liabilities	(10)
Fair value, net derivative assets		9
FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	29	20
IPL [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	16	18	26
IPL [Member] | Excluding FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative liabilities	(9)
Fair value, net derivative assets		8
IPL [Member] | FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	25	10
WPL [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	3	11	$ 3
WPL [Member] | Excluding FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative liabilities	(1)
Fair value, net derivative assets		1
WPL [Member] | FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	$ 4	$ 10

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Long-term Purchase Commitment [Line Items]
Equity income from unconsolidated investments, net	$ 51	$ 62	$ 61
Whiting Petroleum Affiliate [Member]
Long-term Purchase Commitment [Line Items]
Partnership share, percent	6%
Obligations, maximum	$ 58
Credit loss liability	5
Capital Purchase Commitment [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	184
WPL [Member] | Capital Purchase Commitment [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	180
Indemnification Agreement [Member]
Long-term Purchase Commitment [Line Items]
Obligations, maximum	59
Indemnification Agreement [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Obligations, maximum	17
FERC [Member]
Long-term Purchase Commitment [Line Items]
Base return on equity, percentage			10.02%	9.88%
Equity income from unconsolidated investments, net	$ 6

Commitments And Contingencies_3

Commitments And Contingencies (Other Purchase Commitments) (Details) $ in Millions	Dec. 31, 2022 USD ($)
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	$ 719
Minimum future commitments, 2024	373
Minimum future commitments, 2025	230
Minimum future commitments, 2026	148
Minimum future commitments, 2027	90
Minimum future commitments, Thereafter	233
Minimum future commitments, Total	1,793
Individual commitments incurred	1
Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	558
Minimum future commitments, 2024	297
Minimum future commitments, 2025	199
Minimum future commitments, 2026	136
Minimum future commitments, 2027	85
Minimum future commitments, Thereafter	209
Minimum future commitments, Total	1,484
Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	89
Minimum future commitments, 2024	64
Minimum future commitments, 2025	22
Minimum future commitments, 2026	3
Minimum future commitments, 2027	3
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	181
Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	72
Minimum future commitments, 2024	12
Minimum future commitments, 2025	9
Minimum future commitments, 2026	9
Minimum future commitments, 2027	2
Minimum future commitments, Thereafter	24
Minimum future commitments, Total	128
IPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	392
Minimum future commitments, 2024	195
Minimum future commitments, 2025	107
Minimum future commitments, 2026	53
Minimum future commitments, 2027	41
Minimum future commitments, Thereafter	61
Minimum future commitments, Total	849
IPL [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	319
Minimum future commitments, 2024	167
Minimum future commitments, 2025	85
Minimum future commitments, 2026	48
Minimum future commitments, 2027	36
Minimum future commitments, Thereafter	39
Minimum future commitments, Total	694
IPL [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	45
Minimum future commitments, 2024	26
Minimum future commitments, 2025	20
Minimum future commitments, 2026	3
Minimum future commitments, 2027	3
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	97
IPL [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	28
Minimum future commitments, 2024	2
Minimum future commitments, 2025	2
Minimum future commitments, 2026	2
Minimum future commitments, 2027	2
Minimum future commitments, Thereafter	22
Minimum future commitments, Total	58
WPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	311
Minimum future commitments, 2024	169
Minimum future commitments, 2025	117
Minimum future commitments, 2026	89
Minimum future commitments, 2027	49
Minimum future commitments, Thereafter	170
Minimum future commitments, Total	905
WPL [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	239
Minimum future commitments, 2024	130
Minimum future commitments, 2025	114
Minimum future commitments, 2026	88
Minimum future commitments, 2027	49
Minimum future commitments, Thereafter	170
Minimum future commitments, Total	790
WPL [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	44
Minimum future commitments, 2024	38
Minimum future commitments, 2025	2
Minimum future commitments, 2026	0
Minimum future commitments, 2027	0
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	84
WPL [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2023	28
Minimum future commitments, 2024	1
Minimum future commitments, 2025	1
Minimum future commitments, 2026	1
Minimum future commitments, 2027	0
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	$ 31

Commitments And Contingencies_4

Commitments And Contingencies (Schedule Of Environmental Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)
Current and non-current environmental liabilities	$ 11
IPL [Member]
Current and non-current environmental liabilities	8
Minimum [Member]
Range of estimated future costs	9
Minimum [Member] | IPL [Member]
Range of estimated future costs	6
Maximum [Member]
Range of estimated future costs	25
Maximum [Member] | IPL [Member]
Range of estimated future costs	$ 19

Segments Of Business (Narrative

Segments Of Business (Narrative) (Details)	12 Months Ended
	Dec. 31, 2022 segment
Utility Business [Member]
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)	3
IPL [Member]
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)	3
WPL [Member]
Segment Reporting Information [Line Items]
Number of reportable segments (in segments)	3

Segments Of Business (Schedule

Segments Of Business (Schedule Of Segment Of Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 4,205	$ 3,669	$ 3,416
Depreciation and amortization	671	657	615
Operating income (loss)	928	795	740
Interest expense	325	277	275
Equity income from unconsolidated investments, net	(51)	(62)	(61)
Income tax expense (benefit)	22	(74)	(57)
Net income attributable to common shareowners	686	659	614
Total assets	20,163	18,553	17,710
Investments in equity method subsidiaries	542	508	476
Construction and acquisition expenditures	1,484	1,169	1,366
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	2,256	2,063	1,947
Operating income (loss)	453	460	410
Interest expense	148	139	139
Income tax expense (benefit)	(50)	(36)	(47)
Net income attributable to common shareowners	360	350	324
Total assets	10,075	9,996
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,856	1,523	1,395
Operating income (loss)	452	308	306
Interest expense	121	105	104
Income tax expense (benefit)	66	(51)	(19)
Total assets	8,987	7,518
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	3,421	3,081	2,920
Depreciation and amortization	601	591	556
Operating income (loss)	805	716	643
Equity income from unconsolidated investments, net	(1)	(2)	(2)
Total assets	16,571	14,924	14,358
Investments in equity method subsidiaries	20	17	11
Construction and acquisition expenditures	1,318	980	1,109
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,859	1,752	1,695
Depreciation and amortization	342	338	321
Operating income (loss)	397	420	358
Total assets	8,686	8,602	8,518
Construction and acquisition expenditures	336	342	626
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,562	1,329	1,225
Depreciation and amortization	259	253	235
Operating income (loss)	408	296	285
Total assets	7,885	6,322	5,840
Construction and acquisition expenditures	982	638	483
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	642	456	373
Depreciation and amortization	56	54	49
Operating income (loss)	97	63	74
Equity income from unconsolidated investments, net	0	0	0
Total assets	1,631	1,487	1,413
Investments in equity method subsidiaries	0	0	0
Construction and acquisition expenditures	74	90	182
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	351	265	208
Depreciation and amortization	32	31	30
Operating income (loss)	53	43	50
Total assets	872	819	766
Construction and acquisition expenditures	36	42	59
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	291	191	165
Depreciation and amortization	24	23	19
Operating income (loss)	44	20	24
Total assets	759	668	647
Construction and acquisition expenditures	38	48	123
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	49	49	49
Depreciation and amortization	7	6	5
Operating income (loss)	3	(11)	(1)
Equity income from unconsolidated investments, net	0	0	0
Total assets	860	1,103	990
Investments in equity method subsidiaries	0	0	0
Construction and acquisition expenditures	0	0	2
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	46	46	44
Depreciation and amortization	7	6	5
Operating income (loss)	3	(3)	2
Total assets	517	575	565
Construction and acquisition expenditures	0	0	2
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	3	3	5
Depreciation and amortization	0	0	0
Operating income (loss)	0	(8)	(3)
Total assets	343	528	425
Construction and acquisition expenditures	0	0	0
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	4,112	3,586	3,342
Depreciation and amortization	664	651	610
Operating income (loss)	905	768	716
Interest expense	269	244	243
Equity income from unconsolidated investments, net	(1)	(2)	(2)
Income tax expense (benefit)	16	(87)	(66)
Net income attributable to common shareowners	675	618	573
Total assets	19,062	17,514	16,761
Investments in equity method subsidiaries	20	17	11
Construction and acquisition expenditures	1,392	1,070	1,293
Utility Business [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	2,256	2,063	1,947
Depreciation and amortization	381	375	356
Operating income (loss)	453	460	410
Interest expense	148	139	139
Income tax expense (benefit)	(50)	(36)	(47)
Net income attributable to common shareowners	360	350	324
Total assets	10,075	9,996	9,849
Construction and acquisition expenditures	372	384	687
Utility Business [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,856	1,523	1,395
Depreciation and amortization	283	276	254
Operating income (loss)	452	308	306
Interest expense	121	105	104
Income tax expense (benefit)	66	(51)	(19)
Net income attributable to common shareowners	315	268	249
Total assets	8,987	7,518	6,912
Construction and acquisition expenditures	1,020	686	606
Non-Utility [Member]
Segment Reporting Information [Line Items]
Revenues	93	83	74
Depreciation and amortization	7	6	5
Operating income (loss)	23	27	24
Interest expense	56	33	32
Equity income from unconsolidated investments, net	(50)	(60)	(59)
Income tax expense (benefit)	6	13	9
Net income attributable to common shareowners	11	41	41
Total assets	1,101	1,039	949
Investments in equity method subsidiaries	522	491	465
Construction and acquisition expenditures	$ 92	$ 99	$ 73

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - WPL [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Receipt of construction deposits	$ 46
WPL Owed ATC [Member]
Related Party Transaction [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	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Administrative and General Services Billings [Member] | IPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 181	$ 180	$ 176
Administrative and General Services Billings [Member] | WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	155	154	142
Transmission Sales Credited [Member] | IPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	19	22	35
Transmission Sales Credited [Member] | WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	74	23	3
Transmission Purchases Billed [Member] | IPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	435	441	329
Transmission Purchases Billed [Member] | WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 174	$ 116	$ 108

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
IPL [Member]
Related Party Transaction [Line Items]
Intercompany payables to Corporate Services	$ 103	$ 110
WPL [Member]
Related Party Transaction [Line Items]
Intercompany payables to Corporate Services	$ 56	$ 83

Related Parties (Related Amount

Related Parties (Related Amounts Billed Between Parties) (Details) - WPL [Member] - ATC LLC [Member] - Equity Method Investment [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
ATC Billings To WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 140	$ 122	$ 108
WPL Billings To ATC [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 18	$ 18	$ 10

Condensed Parent Company Fina_3

Condensed Parent Company Financial Statements (Condensed Statements Of Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating expenses	$ 3,277	$ 2,874	$ 2,676
Operating income (loss)	928	795	740
Other (income) and deductions:
Equity earnings from consolidated subsidiaries	(51)	(62)	(61)
Interest expense	325	277	275
Other	6	5	14
Total other (income) and deductions	220	195	173
Income before income taxes	708	600	567
Income tax benefit	22	(74)	(57)
Net income	686	674	624
Parent Company [Member]
Operating expenses	9	5	7
Operating income (loss)	(9)	(5)	(7)
Other (income) and deductions:
Equity earnings from consolidated subsidiaries	(707)	(664)	(625)
Interest expense	6	1	2
Other	(1)	(1)	(4)
Total other (income) and deductions	(700)	(662)	(619)
Income before income taxes	691	657	612
Income tax benefit	2	(5)	(4)
Net income	$ 689	$ 662	$ 616

Condensed Parent Company Fina_4

Condensed Parent Company Financial Statements (Condensed Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Other	$ 223	$ 240
Total current assets	1,250	1,069
Investments:
Other	201	179
Total investments	559	517
Other assets	2,107	1,980
Total assets	20,163	18,553	$ 17,710
Current liabilities:
Commercial paper	642	515
Other	351	284
Total current liabilities	2,363	2,054
Other liabilities	518	388
Common Equity:
Retained earnings	3,509	3,250
Shares in deferred compensation trust	(13)	(12)
Total common equity	6,276	5,990
Total liabilities and equity	20,163	18,553
Parent Company [Member]
Current assets:
Notes receivable from affiliated companies	65	16
Other	1	5
Total current assets	66	21
Investments:
Investments in consolidated subsidiaries	7,801	7,061
Other	2	2
Total investments	7,803	7,063
Other assets	97	96
Total assets	7,966	7,180
Current liabilities:
Commercial paper	352	279
Notes payable to affiliated companies	1,318	900
Other	10	4
Total current liabilities	1,680	1,183
Other liabilities	1	2
Common Equity:
Common stock and additional paid-in capital	2,780	2,752
Retained earnings	3,518	3,255
Shares in deferred compensation trust	(13)	(12)
Total common equity	6,285	5,995
Total liabilities and equity	$ 7,966	$ 7,180

Condensed Parent Company Fina_5

Condensed Parent Company Financial Statements (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net cash flows from operating activities	$ 486	$ 582	$ 501
Cash flows from (used for) investing activities:
Dividends from consolidated subsidiaries in excess of equity earnings	(47)	(61)	(43)
Net cash flows from (used for) investing activities	(933)	(728)	(951)
Cash flows used for financing activities:
Common stock dividends	(428)	(403)	(377)
Proceeds from issuance of common stock, net	25	28	247
Net change in commercial paper	127	126	52
Other	2	(13)	(27)
Net cash flows from (used for) financing activities	431	130	488
Net increase (decrease) in cash, cash equivalents and restricted cash	(16)	(16)	38
Cash, cash equivalents and restricted cash at beginning of period	40	56	18
Cash, cash equivalents and restricted cash at end of period	24	40	56
Supplemental cash flows information:
Interest	(311)	(272)	(274)
Income taxes, net	(6)	(3)	5
Parent Company [Member]
Net cash flows from operating activities	492	494	396
Cash flows from (used for) investing activities:
Capital contributions to consolidated subsidiaries	(530)	(295)	(429)
Net change in notes receivable from and payable to affiliates	369	(21)	201
Dividends from consolidated subsidiaries in excess of equity earnings	0	50	0
Net cash flows from (used for) investing activities	(161)	(266)	(228)
Cash flows used for financing activities:
Common stock dividends	(428)	(403)	(377)
Proceeds from issuance of common stock, net	25	28	247
Net change in commercial paper	73	147	(37)
Other	(1)	0	(1)
Net cash flows from (used for) financing activities	(331)	(228)	(168)
Net increase (decrease) in cash, cash equivalents and restricted cash	0	0	0
Cash, cash equivalents and restricted cash at beginning of period	0	0	0
Cash, cash equivalents and restricted cash at end of period	0	0	0
Supplemental cash flows information:
Interest	(6)	(1)	(2)
Income taxes, net	$ 15	$ 4	$ 10

Valuation And Qualifying Acco_2

Valuation And Qualifying Accounts and Reserves (Details) - Accumulated Provision for Uncollectible Accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 11	$ 18	$ 7
Charged to Expense	17	12	25
Charged to Other Accounts	0	0	9
Deductions	21	19	23
Ending Balance	7	11	18
IPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1	1	1
Charged to Expense	7	6	18
Charged to Other Accounts	0	0	0
Deductions	8	6	18
Ending Balance	0	1	1
WPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	10	17	6
Charged to Expense	10	6	7
Charged to Other Accounts	0	0	9
Deductions	13	13	5
Ending Balance	$ 7	$ 10	$ 17