Interstate Power & Light (IPLDP) 10-K 18 Feb 22 2021 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Jan. 31, 2022	Jun. 30, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
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			$ 13,900
Entity Common Stock, Shares Outstanding		250,478,681
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference	Portions of the Proxy Statement relating to Alliant Energy Corporation’s 2022 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, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Electric utility	$ 3,081	$ 2,920	$ 3,064
Gas utility	456	373	455
Other utility	49	49	46
Non-utility	83	74	83
Total revenues	3,669	3,416	3,648
Operating expenses:
Electric production fuel and purchased power	642	652	777
Electric transmission service	537	449	481
Cost of gas sold	258	182	222
Other operation and maintenance	676	670	712
Depreciation and amortization	657	615	567
Taxes other than income taxes	104	108	111
Total operating expenses	2,874	2,676	2,870
Operating income (loss)	795	740	778
Other (income) and deductions:
Interest expense	277	275	273
Equity income from unconsolidated investments, net	(62)	(61)	(53)
Allowance for funds used during construction	(25)	(55)	(93)
Other	5	14	15
Total other (income) and deductions	195	173	142
Income before income taxes	600	567	636
Income tax expense (benefit)	(74)	(57)	69
Net income	674	624	567
Preferred dividend requirements of Interstate Power and Light Company	15	10	10
Net income attributable to common shareowners	$ 659	$ 614	$ 557
Weighted average number of common shares outstanding:
Basic (in shares)	250.2	248.4	238.5
Diluted (in shares)	250.7	248.7	239
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 2.63	$ 2.47	$ 2.34
Diluted (in dollars per share)	$ 2.63	$ 2.47	$ 2.33
IPL [Member]
Revenues:
Electric utility	$ 1,752	$ 1,695	$ 1,781
Gas utility	265	208	264
Other utility	46	44	44
Total revenues	2,063	1,947	2,089
Operating expenses:
Electric production fuel and purchased power	295	352	435
Electric transmission service	367	298	340
Cost of gas sold	149	99	120
Other operation and maintenance	362	375	404
Depreciation and amortization	375	356	327
Taxes other than income taxes	55	57	60
Total operating expenses	1,603	1,537	1,686
Operating income (loss)	460	410	403
Other (income) and deductions:
Interest expense	139	139	127
Allowance for funds used during construction	(9)	(24)	(50)
Other	1	8	8
Total other (income) and deductions	131	123	85
Income before income taxes	329	287	318
Income tax expense (benefit)	(36)	(47)	24
Net income	365	334	294
Preferred dividend requirements of Interstate Power and Light Company	15	10	10
Net income attributable to common shareowners	350	324	284
WPL [Member]
Revenues:
Electric utility	1,329	1,225	1,283
Gas utility	191	165	191
Other utility	3	5	2
Total revenues	1,523	1,395	1,476
Operating expenses:
Electric production fuel and purchased power	347	300	342
Electric transmission service	170	151	141
Cost of gas sold	109	83	102
Other operation and maintenance	268	254	261
Depreciation and amortization	276	254	236
Taxes other than income taxes	45	47	47
Total operating expenses	1,215	1,089	1,129
Operating income (loss)	308	306	347
Other (income) and deductions:
Interest expense	105	104	102
Allowance for funds used during construction	(16)	(31)	(43)
Other	2	3	6
Total other (income) and deductions	91	76	65
Income before income taxes	217	230	282
Income tax expense (benefit)	(51)	(19)	49
Net income	$ 268	$ 249	$ 233

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 39	$ 54
Accounts receivable, less allowance for expected credit losses	440	412
Production fuel, at weighted average cost	51	66
Gas stored underground, at weighted average cost	82	46
Materials and supplies, at weighted average cost	113	105
Regulatory assets	104	81
Other	240	123
Total current assets	1,069	887
Property, plant and equipment, net	14,987	14,336
Investments:
ATC Holdings	338	331
Other	179	154
Total investments	517	485
Other assets:
Regulatory assets	1,836	1,929
Deferred charges and other	144	73
Total other assets	1,980	2,002
Total assets	18,553	17,710
Current liabilities:
Current maturities of long-term debt	633	8
Commercial paper	515	389
Accounts payable	436	377
Accrued taxes	58	67
Regulatory liabilities	186	249
Other	226	207
Total current liabilities	2,054	1,297
Long-term debt, net (excluding current portion)	6,735	6,769
Other liabilities:
Deferred tax liabilities	1,927	1,814
Regulatory liabilities	1,085	1,057
Pension and other benefit obligations	374	511
Other	388	374
Total other liabilities	3,774	3,756
Commitments and contingencies (Note 17)
Common equity:
Common stock	3	2
Additional paid-in capital	2,749	2,704
Retained earnings	3,250	2,994
Accumulated other comprehensive loss	0	(1)
Shares in deferred compensation trust - 383,532 and 380,542 shares at a weighted average cost of $30.59 and $28.73 per share	(12)	(11)
Total common equity	5,990	5,688
Cumulative preferred stock of Interstate Power and Light Company	0	200
Total equity	5,990	5,888
Total liabilities and equity	18,553	17,710
IPL [Member]
Current assets:
Cash and cash equivalents	34	50
Accounts receivable, less allowance for expected credit losses	241	210
Income taxes refunds receivable	8	26
Production fuel, at weighted average cost	29	48
Gas stored underground, at weighted average cost	40	20
Materials and supplies, at weighted average cost	70	63
Regulatory assets	73	52
Other	69	27
Total current assets	564	496
Property, plant and equipment, net	7,983	7,889
Other assets:
Regulatory assets	1,370	1,431
Deferred charges and other	79	33
Total other assets	1,449	1,464
Total assets	9,996	9,849
Current liabilities:
Current maturities of long-term debt	0	0
Commercial paper	0	0
Accounts payable	173	162
Accounts payable to associated companies	39	45
Accrued taxes	56	54
Regulatory liabilities	84	103
Accrued interest	36	34
Other	67	49
Total current liabilities	455	447
Long-term debt, net (excluding current portion)	3,643	3,345
Other liabilities:
Deferred tax liabilities	1,083	1,035
Regulatory liabilities	607	573
Pension and other benefit obligations	127	186
Other	312	299
Total other liabilities	2,129	2,093
Commitments and contingencies (Note 17)
Common equity:
Common stock	33	33
Additional paid-in capital	2,807	2,752
Retained earnings	929	979
Total common equity	3,769	3,764
Cumulative preferred stock of Interstate Power and Light Company	0	200
Total equity	3,769	3,964
Total liabilities and equity	9,996	9,849
WPL [Member]
Current assets:
Cash and cash equivalents	2	3
Accounts receivable, less allowance for expected credit losses	188	192
Production fuel, at weighted average cost	23	18
Gas stored underground, at weighted average cost	42	26
Materials and supplies, at weighted average cost	41	40
Regulatory assets	31	29
Prepaid gross receipts tax	40	42
Other	86	12
Total current assets	453	362
Property, plant and equipment, net	6,538	6,022
Other assets:
Regulatory assets	466	498
Deferred charges and other	61	30
Total other assets	527	528
Total assets	7,518	6,912
Current liabilities:
Current maturities of long-term debt	250	0
Commercial paper	236	257
Accounts payable	190	154
Accounts payable to associated companies	39	35
Regulatory liabilities	102	146
Other	73	82
Total current liabilities	890	674
Long-term debt, net (excluding current portion)	2,179	2,130
Other liabilities:
Deferred tax liabilities	753	702
Regulatory liabilities	478	484
Pension and other benefit obligations	159	222
Other	236	222
Total other liabilities	1,626	1,630
Commitments and contingencies (Note 17)
Common equity:
Common stock	66	66
Additional paid-in capital	1,704	1,459
Retained earnings	1,053	953
Total common equity	2,823	2,478
Total equity	2,823	2,478
Total liabilities and equity	$ 7,518	$ 6,912

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	480,000,000	480,000,000
Common stock, shares outstanding (in shares)	250,474,529	249,868,415
Shares in deferred compensation trust (in shares)	383,532	380,542
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 30.59	$ 28.73
IPL [Member]
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	24,000,000	24,000,000
Common stock, shares outstanding (in shares)	13,370,788	13,370,788
WPL [Member]
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	18,000,000	18,000,000
Common stock, shares outstanding (in shares)	13,236,601	13,236,601

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from (used for) operating activities:
Net income	$ 674	$ 624	$ 567
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	657	615	567
Deferred tax expense (benefit) and tax credits	(78)	(66)	56
Equity component of allowance for funds used during construction	(18)	(39)	(66)
Other	35	37	20
Other changes in assets and liabilities:
Accounts receivable	(530)	(468)	(472)
Derivative assets	(142)	(7)	2
Regulatory assets	51	(130)	(16)
Regulatory liabilities	(66)	(113)	(40)
Deferred income taxes	193	171	54
Pension and other benefit obligations	(137)	27	(25)
DAEC PPA amendment buyout payment	0	(110)	0
Other	(57)	(40)	13
Net cash flows from (used for) operating activities	582	501	660
Cash flows from (used for) investing activities:
Utility construction and acquisition expenditures	(1,070)	(1,293)	(1,539)
Other construction and acquisition expenditures	(99)	(73)	(101)
Cash receipts on sold receivables	502	458	413
Other	(61)	(43)	(60)
Net cash flows from (used for) investing activities	(728)	(951)	(1,287)
Cash flows from financing activities:
Common stock dividends	(403)	(377)	(337)
Proceeds from issuance of common stock, net	28	247	390
Payments to redeem cumulative preferred stock of IPL	(200)	0	0
Proceeds from issuance of long-term debt	600	1,250	950
Payments to retire long-term debt	(8)	(657)	(256)
Net change in commercial paper	126	52	(104)
Other	(13)	(27)	(24)
Net cash flows from (used for) financing activities	130	488	619
Net increase (decrease) in cash, cash equivalents and restricted cash	(16)	38	(8)
Cash, cash equivalents and restricted cash at beginning of period	56	18	26
Cash, cash equivalents and restricted cash at end of period	40	56	18
Supplemental cash flows information:
Interest	(272)	(274)	(268)
Income taxes, net	(3)	5	21
Significant non-cash investing and financing activities:
Accrued capital expenditures	141	131	196
Beneficial interest obtained in exchange for securitized accounts receivable	214	188	188
IPL [Member]
Cash flows from (used for) operating activities:
Net income	365	334	294
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	375	356	327
Deferred tax expense (benefit) and tax credits	(14)	(52)	15
Equity component of allowance for funds used during construction	(7)	(17)	(35)
Other	11	12	1
Other changes in assets and liabilities:
Accounts receivable	(539)	(466)	(467)
Derivative assets	(55)	(7)	(5)
Regulatory assets	30	(93)	(11)
Accounts payable	15	6	(21)
Regulatory liabilities	1	(20)	2
Deferred income taxes	62	79	35
Pension and other benefit obligations	(59)	18	(11)
DAEC PPA amendment buyout payment	0	(110)	0
Other	(32)	(46)	49
Net cash flows from (used for) operating activities	153	(6)	173
Cash flows from (used for) investing activities:
Utility construction and acquisition expenditures	(384)	(687)	(1,020)
Cash receipts on sold receivables	502	458	413
Other	(27)	(72)	(60)
Net cash flows from (used for) investing activities	91	(301)	(667)
Cash flows from financing activities:
Common stock dividends	(400)	(236)	(168)
Capital contributions from parent	50	404	125
Payments to redeem cumulative preferred stock of IPL	(200)	0	0
Proceeds from issuance of long-term debt	300	400	600
Payments to retire long-term debt	0	(200)	0
Net change in commercial paper	0	0	(50)
Other	(10)	(20)	(16)
Net cash flows from (used for) financing activities	(260)	348	491
Net increase (decrease) in cash, cash equivalents and restricted cash	(16)	41	(3)
Cash, cash equivalents and restricted cash at beginning of period	50	9	12
Cash, cash equivalents and restricted cash at end of period	34	50	9
Supplemental cash flows information:
Interest	(138)	(141)	(122)
Income taxes, net	47	(18)	7
Significant non-cash investing and financing activities:
Accrued capital expenditures	57	73	112
Beneficial interest obtained in exchange for securitized accounts receivable	214	188	188
WPL [Member]
Cash flows from (used for) operating activities:
Net income	268	249	233
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	276	254	236
Deferred tax expense (benefit) and tax credits	(79)	(15)	24
Other	11	2	(12)
Other changes in assets and liabilities:
Derivative assets	(87)	0	6
Regulatory liabilities	(67)	(93)	(42)
Deferred income taxes	132	90	20
Pension and other benefit obligations	(63)	11	(7)
Other	(20)	(32)	(35)
Net cash flows from (used for) operating activities	371	466	423
Cash flows from (used for) investing activities:
Utility construction and acquisition expenditures	(686)	(606)	(519)
Other	(30)	(7)	(38)
Net cash flows from (used for) investing activities	(716)	(613)	(557)
Cash flows from financing activities:
Common stock dividends	(168)	(160)	(144)
Capital contributions from parent	245	25	125
Proceeds from issuance of long-term debt	300	350	350
Payments to retire long-term debt	0	(150)	(250)
Net change in commercial paper	(21)	89	63
Other	(12)	(8)	(15)
Net cash flows from (used for) financing activities	344	146	129
Net increase (decrease) in cash, cash equivalents and restricted cash	(1)	(1)	(5)
Cash, cash equivalents and restricted cash at beginning of period	3	4	9
Cash, cash equivalents and restricted cash at end of period	2	3	4
Supplemental cash flows information:
Interest	(101)	(102)	(103)
Income taxes, net	(38)	13	(29)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 81	$ 55	$ 82

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]
Beginning balance at Dec. 31, 2018					$ 2	$ 33	$ 66	$ 2,046	$ 2,223	$ 1,309	$ 2,546		$ 775	$ 775	$ 2	$ (10)	$ 200	$ 200
Beginning balance at Dec. 31, 2018	$ 4,786		$ 3,231	$ 2,150
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Net income attributable to common shareowners	557		284								557		284
Net income	567		294	233										233
Common stock dividends	(337)		(168)	(144)							(337)		(168)	(144)
Equity forward settlements and Shareowner Direct Plan issuances	390							390
Capital contributions from parent			125	125					125	125
Equity-based compensation plans and other	10							10
Payments to redeem cumulative preferred stock of IPL	0		0
Other comprehensive income (loss), net of tax	(1)														(1)
Ending balance at Dec. 31, 2019					2	33	66	2,446	2,348	1,434	2,766		891	864	1	(10)	200	200
Ending balance at Dec. 31, 2019	5,405		3,472	2,364
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Adoption of new accounting standard, net of tax		$ (9)										$ (9)
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)
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	5,688		3,764	2,478	2	33	66	2,704	2,752	1,459	2,994		979	953	(1)	(11)	200	200
Ending balance at Dec. 31, 2020	5,888		3,964	2,478
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Adoption of new accounting standard, net of tax	2,994		979	953
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)
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
Ending balance at Dec. 31, 2021	5,990		3,769	2,823
Increase (Decrease) in Shareowners' Equity [Roll Forward]
Adoption of new accounting standard, net of tax	$ 3,250		$ 929	$ 1,053

Consolidated Statements of Co_2

Consolidated Statements of Common Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Common stock dividends (in dollars per share)	$ 1.61	$ 1.52	$ 1.42

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
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 subsidiary. 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, which began operations in 2021. 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 coalition with different energy companies across the U.S., working together to help identify and research innovative products, 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. In March 2020, COVID-19 was declared a global pandemic, which has resulted in widespread travel restrictions, closures of commercial spaces and industrial facilities, and more people working from home in Alliant Energy’s service territories. For 2020 and 2021, Alliant Energy, IPL and WPL considered the impact of COVID-19 on their overall business operations, financial condition, results of operations and cash flows, along with assumptions and estimates used. In 2020, Alliant Energy, IPL and WPL experienced higher electric residential sales and lower electric commercial and industrial sales as a result of the pandemic. In 2021, changes in COVID-19 impacts resulted in lower electric residential sales and higher electric commercial and industrial sales. The degree to which the COVID-19 pandemic may impact Alliant Energy, IPL and WPL in the future is currently unknown and will depend on future developments of the pandemic as well as possible additional actions by government and regulatory authorities. 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. Investment tax credits are deferred and amortized to income over the average lives of the related property. 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. Other tax credits reduce income tax expense in the year claimed. 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 2021, 2020 and 2019. 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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6% 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: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9% 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. 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 West Riverside and 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, 2021, 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. Purchased 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 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. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliations of any under-/over-collection of energy efficiency costs from prior periods are also addressed in WPL’s periodic rate proceedings. 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 - Effective with the implementation of final rates covering the 2020 forward-looking Test Period, IPL recovers a return of, as well as earn a return on, its new 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 the new 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 subsidiary. 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, which began operations in 2021. 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 coalition with different energy companies across the U.S., working together to help identify and research innovative products, 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. In March 2020, COVID-19 was declared a global pandemic, which has resulted in widespread travel restrictions, closures of commercial spaces and industrial facilities, and more people working from home in Alliant Energy’s service territories. For 2020 and 2021, Alliant Energy, IPL and WPL considered the impact of COVID-19 on their overall business operations, financial condition, results of operations and cash flows, along with assumptions and estimates used. In 2020, Alliant Energy, IPL and WPL experienced higher electric residential sales and lower electric commercial and industrial sales as a result of the pandemic. In 2021, changes in COVID-19 impacts resulted in lower electric residential sales and higher electric commercial and industrial sales. The degree to which the COVID-19 pandemic may impact Alliant Energy, IPL and WPL in the future is currently unknown and will depend on future developments of the pandemic as well as possible additional actions by government and regulatory authorities. 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. Investment tax credits are deferred and amortized to income over the average lives of the related property. 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. Other tax credits reduce income tax expense in the year claimed. 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 2021, 2020 and 2019. 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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6% 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: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9% 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. 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 West Riverside and 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, 2021, 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. Purchased 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 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. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliations of any under-/over-collection of energy efficiency costs from prior periods are also addressed in WPL’s periodic rate proceedings. 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 - Effective with the implementation of final rates covering the 2020 forward-looking Test Period, IPL recovers a return of, as well as earn a return on, its new 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 the new 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 subsidiary. 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, which began operations in 2021. 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 coalition with different energy companies across the U.S., working together to help identify and research innovative products, 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. In March 2020, COVID-19 was declared a global pandemic, which has resulted in widespread travel restrictions, closures of commercial spaces and industrial facilities, and more people working from home in Alliant Energy’s service territories. For 2020 and 2021, Alliant Energy, IPL and WPL considered the impact of COVID-19 on their overall business operations, financial condition, results of operations and cash flows, along with assumptions and estimates used. In 2020, Alliant Energy, IPL and WPL experienced higher electric residential sales and lower electric commercial and industrial sales as a result of the pandemic. In 2021, changes in COVID-19 impacts resulted in lower electric residential sales and higher electric commercial and industrial sales. The degree to which the COVID-19 pandemic may impact Alliant Energy, IPL and WPL in the future is currently unknown and will depend on future developments of the pandemic as well as possible additional actions by government and regulatory authorities. 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. Investment tax credits are deferred and amortized to income over the average lives of the related property. 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. Other tax credits reduce income tax expense in the year claimed. 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 2021, 2020 and 2019. 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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6% 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: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9% 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. 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 West Riverside and 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, 2021, 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. Purchased 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 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. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliations of any under-/over-collection of energy efficiency costs from prior periods are also addressed in WPL’s periodic rate proceedings. 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 - Effective with the implementation of final rates covering the 2020 forward-looking Test Period, IPL recovers a return of, as well as earn a return on, its new 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 the new 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, 2021
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, 2021 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 2021 2020 2021 2020 2021 2020 Tax-related $934 $890 $884 $843 $50 $47 Pension and OPEB costs 462 580 228 291 234 289 AROs 128 119 89 81 39 38 Assets retired early 92 113 66 77 26 36 IPL’s DAEC PPA amendment 90 110 90 110 — — WPL’s Western Wisconsin gas distribution expansion investments 52 55 — — 52 55 Commodity cost recovery 42 4 2 1 40 3 Derivatives 8 26 4 13 4 13 Other 132 113 80 67 52 46 $1,940 $2,010 $1,443 $1,483 $497 $527 At December 31, 2021, IPL and WPL had $75 million and $13 million, respectively, of regulatory assets that were not earning a return. 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. 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. 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. 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, 2021 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $19 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 18 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 29 Return of remaining net book value through 2028 IUB and FERC WPL Nelson Dewey Units 1 and 2 and Edgewater Unit 3 2015 6 Return of and return on remaining net book value through 2022 PSCW and FERC WPL Edgewater Unit 4 2018 20 Return of and return on remaining net book value through 2028 PSCW and FERC IPL’s DAEC PPA Amendment - In September 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. 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, 2021. 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. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2021 2020 2021 2020 2021 2020 Tax-related $585 $732 $312 $331 $273 $401 Cost of removal obligations 384 367 252 238 132 129 Derivatives 166 28 77 25 89 3 Electric transmission cost recovery 51 68 27 39 24 29 WPL’s West Riverside liquidated damages 36 38 — — 36 38 Other 49 73 23 43 26 30 $1,271 $1,306 $691 $676 $580 $630 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. In 2021, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities decreased primarily due to returning a portion of these excess deferred tax benefits back 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. 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. 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 December 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. 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 and permanent repairs to the system continue. As of December 31, 2021, 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, 2021, 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 intervenor groups 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 intervenor groups 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 intervenor groups. 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 Fuel-related Rate Filing (2020 Forward-looking Test Period) - In December 2019, WPL received an order from the PSCW authorizing an annual retail electric rate decrease of $29 million, or approximately 2%, effective January 1, 2020. The decrease primarily reflected a change in expected fuel-related costs in 2020.
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, 2021 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 2021 2020 2021 2020 2021 2020 Tax-related $934 $890 $884 $843 $50 $47 Pension and OPEB costs 462 580 228 291 234 289 AROs 128 119 89 81 39 38 Assets retired early 92 113 66 77 26 36 IPL’s DAEC PPA amendment 90 110 90 110 — — WPL’s Western Wisconsin gas distribution expansion investments 52 55 — — 52 55 Commodity cost recovery 42 4 2 1 40 3 Derivatives 8 26 4 13 4 13 Other 132 113 80 67 52 46 $1,940 $2,010 $1,443 $1,483 $497 $527 At December 31, 2021, IPL and WPL had $75 million and $13 million, respectively, of regulatory assets that were not earning a return. 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. 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. 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. 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, 2021 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $19 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 18 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 29 Return of remaining net book value through 2028 IUB and FERC WPL Nelson Dewey Units 1 and 2 and Edgewater Unit 3 2015 6 Return of and return on remaining net book value through 2022 PSCW and FERC WPL Edgewater Unit 4 2018 20 Return of and return on remaining net book value through 2028 PSCW and FERC IPL’s DAEC PPA Amendment - In September 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. 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, 2021. 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. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2021 2020 2021 2020 2021 2020 Tax-related $585 $732 $312 $331 $273 $401 Cost of removal obligations 384 367 252 238 132 129 Derivatives 166 28 77 25 89 3 Electric transmission cost recovery 51 68 27 39 24 29 WPL’s West Riverside liquidated damages 36 38 — — 36 38 Other 49 73 23 43 26 30 $1,271 $1,306 $691 $676 $580 $630 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. In 2021, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities decreased primarily due to returning a portion of these excess deferred tax benefits back 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. 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. 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 December 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. 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 and permanent repairs to the system continue. As of December 31, 2021, 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, 2021, 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 intervenor groups 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 intervenor groups 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 intervenor groups. 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 Fuel-related Rate Filing (2020 Forward-looking Test Period) - In December 2019, WPL received an order from the PSCW authorizing an annual retail electric rate decrease of $29 million, or approximately 2%, effective January 1, 2020. The decrease primarily reflected a change in expected fuel-related costs in 2020.
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, 2021 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 2021 2020 2021 2020 2021 2020 Tax-related $934 $890 $884 $843 $50 $47 Pension and OPEB costs 462 580 228 291 234 289 AROs 128 119 89 81 39 38 Assets retired early 92 113 66 77 26 36 IPL’s DAEC PPA amendment 90 110 90 110 — — WPL’s Western Wisconsin gas distribution expansion investments 52 55 — — 52 55 Commodity cost recovery 42 4 2 1 40 3 Derivatives 8 26 4 13 4 13 Other 132 113 80 67 52 46 $1,940 $2,010 $1,443 $1,483 $497 $527 At December 31, 2021, IPL and WPL had $75 million and $13 million, respectively, of regulatory assets that were not earning a return. 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. 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. 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. 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, 2021 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $19 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 18 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 29 Return of remaining net book value through 2028 IUB and FERC WPL Nelson Dewey Units 1 and 2 and Edgewater Unit 3 2015 6 Return of and return on remaining net book value through 2022 PSCW and FERC WPL Edgewater Unit 4 2018 20 Return of and return on remaining net book value through 2028 PSCW and FERC IPL’s DAEC PPA Amendment - In September 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. 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, 2021. 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. Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL 2021 2020 2021 2020 2021 2020 Tax-related $585 $732 $312 $331 $273 $401 Cost of removal obligations 384 367 252 238 132 129 Derivatives 166 28 77 25 89 3 Electric transmission cost recovery 51 68 27 39 24 29 WPL’s West Riverside liquidated damages 36 38 — — 36 38 Other 49 73 23 43 26 30 $1,271 $1,306 $691 $676 $580 $630 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. In 2021, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities decreased primarily due to returning a portion of these excess deferred tax benefits back 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. 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. 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 December 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. 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 and permanent repairs to the system continue. As of December 31, 2021, 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, 2021, 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 intervenor groups 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 intervenor groups 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 intervenor groups. 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 Fuel-related Rate Filing (2020 Forward-looking Test Period) - In December 2019, WPL received an order from the PSCW authorizing an annual retail electric rate decrease of $29 million, or approximately 2%, effective January 1, 2020. The decrease primarily reflected a change in expected fuel-related costs in 2020.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2021 2020 2021 2020 Utility: Electric plant: Generation in service $7,539 $8,222 $4,922 $4,884 $2,617 $3,338 Distribution in service 6,537 6,216 3,652 3,470 2,885 2,746 Other in service 540 536 363 358 177 178 Anticipated to be retired early (a) 2,094 1,269 487 459 1,607 810 Total electric plant 16,710 16,243 9,424 9,171 7,286 7,072 Gas plant in service 1,636 1,563 878 844 758 719 Other plant in service 621 534 398 354 223 180 Accumulated depreciation (5,263) (4,868) (2,897) (2,671) (2,366) (2,197) Net plant 13,704 13,472 7,803 7,698 5,901 5,774 Leased Sheboygan Falls Energy Facility, net (b) — — — — 21 27 Leased land for solar generation, net 11 — — — 11 — Construction work in progress 778 405 174 185 604 220 Other, net 7 7 6 6 1 1 Total utility 14,500 13,884 7,983 7,889 6,538 6,022 Non-utility and other: Non-utility Generation, net (c) 75 79 — — — — Corporate Services and other, net (d) 412 373 — — — — Total non-utility and other 487 452 — — — — Total property, plant and equipment $14,987 $14,336 $7,983 $7,889 $6,538 $6,022 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing by the end of 2022 and Edgewater Unit 5 by early 2023. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Unit 1 by the end of 2023 and Columbia Unit 2 by the end of 2024. 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, 2021. 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, 2021. As of December 31, 2021, net book values were $245 million for Lansing, $527 million for Edgewater Unit 5, and $460 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $100 million and $95 million for WPL as of December 31, 2021 and 2020, 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 $67 million and $63 million for Alliant Energy as of December 31, 2021 and 2020, respectively. (d) Less accumulated depreciation of $245 million and $210 million for Alliant Energy as of December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Equity $18 $39 $66 $7 $17 $35 $11 $22 $31 Debt 7 16 27 2 7 15 5 9 12 $25 $55 $93 $9 $24 $50 $16 $31 $43 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
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 2021 2020 2021 2020 2021 2020 Utility: Electric plant: Generation in service $7,539 $8,222 $4,922 $4,884 $2,617 $3,338 Distribution in service 6,537 6,216 3,652 3,470 2,885 2,746 Other in service 540 536 363 358 177 178 Anticipated to be retired early (a) 2,094 1,269 487 459 1,607 810 Total electric plant 16,710 16,243 9,424 9,171 7,286 7,072 Gas plant in service 1,636 1,563 878 844 758 719 Other plant in service 621 534 398 354 223 180 Accumulated depreciation (5,263) (4,868) (2,897) (2,671) (2,366) (2,197) Net plant 13,704 13,472 7,803 7,698 5,901 5,774 Leased Sheboygan Falls Energy Facility, net (b) — — — — 21 27 Leased land for solar generation, net 11 — — — 11 — Construction work in progress 778 405 174 185 604 220 Other, net 7 7 6 6 1 1 Total utility 14,500 13,884 7,983 7,889 6,538 6,022 Non-utility and other: Non-utility Generation, net (c) 75 79 — — — — Corporate Services and other, net (d) 412 373 — — — — Total non-utility and other 487 452 — — — — Total property, plant and equipment $14,987 $14,336 $7,983 $7,889 $6,538 $6,022 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing by the end of 2022 and Edgewater Unit 5 by early 2023. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Unit 1 by the end of 2023 and Columbia Unit 2 by the end of 2024. 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, 2021. 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, 2021. As of December 31, 2021, net book values were $245 million for Lansing, $527 million for Edgewater Unit 5, and $460 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $100 million and $95 million for WPL as of December 31, 2021 and 2020, 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 $67 million and $63 million for Alliant Energy as of December 31, 2021 and 2020, respectively. (d) Less accumulated depreciation of $245 million and $210 million for Alliant Energy as of December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Equity $18 $39 $66 $7 $17 $35 $11 $22 $31 Debt 7 16 27 2 7 15 5 9 12 $25 $55 $93 $9 $24 $50 $16 $31 $43
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 2021 2020 2021 2020 2021 2020 Utility: Electric plant: Generation in service $7,539 $8,222 $4,922 $4,884 $2,617 $3,338 Distribution in service 6,537 6,216 3,652 3,470 2,885 2,746 Other in service 540 536 363 358 177 178 Anticipated to be retired early (a) 2,094 1,269 487 459 1,607 810 Total electric plant 16,710 16,243 9,424 9,171 7,286 7,072 Gas plant in service 1,636 1,563 878 844 758 719 Other plant in service 621 534 398 354 223 180 Accumulated depreciation (5,263) (4,868) (2,897) (2,671) (2,366) (2,197) Net plant 13,704 13,472 7,803 7,698 5,901 5,774 Leased Sheboygan Falls Energy Facility, net (b) — — — — 21 27 Leased land for solar generation, net 11 — — — 11 — Construction work in progress 778 405 174 185 604 220 Other, net 7 7 6 6 1 1 Total utility 14,500 13,884 7,983 7,889 6,538 6,022 Non-utility and other: Non-utility Generation, net (c) 75 79 — — — — Corporate Services and other, net (d) 412 373 — — — — Total non-utility and other 487 452 — — — — Total property, plant and equipment $14,987 $14,336 $7,983 $7,889 $6,538 $6,022 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing by the end of 2022 and Edgewater Unit 5 by early 2023. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Unit 1 by the end of 2023 and Columbia Unit 2 by the end of 2024. 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, 2021. 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, 2021. As of December 31, 2021, net book values were $245 million for Lansing, $527 million for Edgewater Unit 5, and $460 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $100 million and $95 million for WPL as of December 31, 2021 and 2020, 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 $67 million and $63 million for Alliant Energy as of December 31, 2021 and 2020, respectively. (d) Less accumulated depreciation of $245 million and $210 million for Alliant Energy as of December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Equity $18 $39 $66 $7 $17 $35 $11 $22 $31 Debt 7 16 27 2 7 15 5 9 12 $25 $55 $93 $9 $24 $50 $16 $31 $43

Jointly-Owned Electric Utility

Jointly-Owned Electric Utility Plant	12 Months Ended
	Dec. 31, 2021
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, 2021 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $599 $214 $11 George Neal Unit 4 25.7% 193 100 2 George Neal Unit 3 28.0% 173 74 3 Louisa Unit 1 4.0% 40 23 — 1,005 411 16 WPL Columbia Units 1-2 53.5% 802 314 6 West Riverside Energy Center and Solar Garden 91.0% 706 33 3 Forward Wind Energy Center 42.6% 118 48 — 1,626 395 9 Alliant Energy $2,631 $806 $25
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, 2021 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $599 $214 $11 George Neal Unit 4 25.7% 193 100 2 George Neal Unit 3 28.0% 173 74 3 Louisa Unit 1 4.0% 40 23 — 1,005 411 16 WPL Columbia Units 1-2 53.5% 802 314 6 West Riverside Energy Center and Solar Garden 91.0% 706 33 3 Forward Wind Energy Center 42.6% 118 48 — 1,626 395 9 Alliant Energy $2,631 $806 $25
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, 2021 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $599 $214 $11 George Neal Unit 4 25.7% 193 100 2 George Neal Unit 3 28.0% 173 74 3 Louisa Unit 1 4.0% 40 23 — 1,005 411 16 WPL Columbia Units 1-2 53.5% 802 314 6 West Riverside Energy Center and Solar Garden 91.0% 706 33 3 Forward Wind Energy Center 42.6% 118 48 — 1,626 395 9 Alliant Energy $2,631 $806 $25

Receivables

Receivables	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2021 2020 2021 2020 Customer $93 $101 $— $— $82 $92 Unbilled utility revenues 91 82 — — 91 82 Deferred proceeds 214 188 214 188 — — Other 53 59 28 23 25 35 Allowance for expected credit losses (11) (18) (1) (1) (10) (17) $440 $412 $241 $210 $188 $192 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. In April 2021, IPL amended and extended through March 2023 the purchase commitment from the third party to which it sells its receivables. 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. Under the Receivables Agreement, IPL has the right to receive cash proceeds, up to a certain limit, from the third party in exchange for the receivables sold. Effective April 2021, the limit on cash proceeds is $110 million. Cash proceeds are used by IPL to meet short-term financing needs, and cannot exceed the current limit or amount of receivables available for sale, whichever is less. As of December 31, 2021, IPL had $109 million of available capacity under its sales of accounts receivable program. 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 2021 2020 2019 2021 2020 2019 Outstanding aggregate cash proceeds $110 $96 $108 $46 $9 $36 As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2021 2020 Customer accounts receivable $125 $114 Unbilled utility revenues 104 92 Receivables sold to third party 229 206 Less: cash proceeds 1 1 Deferred proceeds 228 205 Less: allowance for expected credit losses 14 17 Fair value of deferred proceeds $214 $188 Outstanding receivables past due $22 $27 Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2021 2020 2019 Collections $2,134 $2,025 $2,193 Write-offs, net of recoveries 9 7 19
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 2021 2020 2021 2020 2021 2020 Customer $93 $101 $— $— $82 $92 Unbilled utility revenues 91 82 — — 91 82 Deferred proceeds 214 188 214 188 — — Other 53 59 28 23 25 35 Allowance for expected credit losses (11) (18) (1) (1) (10) (17) $440 $412 $241 $210 $188 $192 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. In April 2021, IPL amended and extended through March 2023 the purchase commitment from the third party to which it sells its receivables. 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. Under the Receivables Agreement, IPL has the right to receive cash proceeds, up to a certain limit, from the third party in exchange for the receivables sold. Effective April 2021, the limit on cash proceeds is $110 million. Cash proceeds are used by IPL to meet short-term financing needs, and cannot exceed the current limit or amount of receivables available for sale, whichever is less. As of December 31, 2021, IPL had $109 million of available capacity under its sales of accounts receivable program. 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 2021 2020 2019 2021 2020 2019 Outstanding aggregate cash proceeds $110 $96 $108 $46 $9 $36 As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2021 2020 Customer accounts receivable $125 $114 Unbilled utility revenues 104 92 Receivables sold to third party 229 206 Less: cash proceeds 1 1 Deferred proceeds 228 205 Less: allowance for expected credit losses 14 17 Fair value of deferred proceeds $214 $188 Outstanding receivables past due $22 $27 Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2021 2020 2019 Collections $2,134 $2,025 $2,193 Write-offs, net of recoveries 9 7 19
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 2021 2020 2021 2020 2021 2020 Customer $93 $101 $— $— $82 $92 Unbilled utility revenues 91 82 — — 91 82 Deferred proceeds 214 188 214 188 — — Other 53 59 28 23 25 35 Allowance for expected credit losses (11) (18) (1) (1) (10) (17) $440 $412 $241 $210 $188 $192

Investments

Investments	12 Months Ended
	Dec. 31, 2021
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, 2021 2021 2020 2021 2020 2019 ATC Holdings 16%, 20% $338 $331 ($43) ($47) ($45) Non-utility wind farm in Oklahoma 50% 99 103 (4) (8) (5) Corporate venture investments Various 52 31 (13) (4) (1) Other Various 19 11 (2) (2) (2) $508 $476 ($62) ($61) ($53) Summary aggregate financial information from the financial statements of these holdings is as follows (in millions): Alliant Energy 2021 2020 2019 Revenues $802 $801 $783 Operating income 357 376 359 Net income 358 343 340 As of December 31: Current assets 112 121 Non-current assets 7,036 6,388 Current liabilities 455 317 Non-current liabilities 3,110 2,997 Noncontrolling interest 247 192 ATC Holdings - As of December 31, 2021, 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. 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 coalition with different energy companies across the U.S., working together to help identify and research innovative products, technologies and business models within the emerging energy economy.

Common Equity

Common Equity	12 Months Ended
	Dec. 31, 2021
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: 2021 2020 2019 Shares outstanding, January 1 249,868,415 245,022,800 236,063,279 Equity forward agreements — 4,275,127 8,358,973 Shareowner Direct Plan 492,565 472,283 501,808 Equity-based compensation plans 113,549 98,205 101,478 Other — — (2,738) Shares outstanding, December 31 250,474,529 249,868,415 245,022,800 At December 31, 2021, Alliant Energy had a total of 14 million shares available for issuance in the aggregate, pursuant to its 2020 OIP, Shareowner Direct Plan and 401(k) Savings Plan. Equity Forward Agreements - In 2018, Alliant Energy entered into forward sale agreements with various counterparties in connection with a public offering of 8,358,973 shares of Alliant Energy common stock. In 2019, Alliant Energy settled $366 million under the forward sale agreements by delivering 8,358,973 shares of newly issued Alliant Energy common stock at a weighted average forward sale price of $43.75 per share. Alliant Energy used the net proceeds from the settlements for general corporate purposes. 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, 2021
Preferred Stock	PREFERRED STOCK IPL is authorized to issue up to 16,000,000 shares of cumulative preferred stock in aggregate. Information related to IPL’s cumulative preferred stock at December 31, 2020 was as follows (dollars in millions): Series Liquidation Preference/Stated Value Shares Authorized Shares Outstanding Carrying Value 5.1% $25 8,000,000 8,000,000 $200 In December 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 STOCK IPL is authorized to issue up to 16,000,000 shares of cumulative preferred stock in aggregate. Information related to IPL’s cumulative preferred stock at December 31, 2020 was as follows (dollars in millions): Series Liquidation Preference/Stated Value Shares Authorized Shares Outstanding Carrying Value 5.1% $25 8,000,000 8,000,000 $200 In December 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, 2021
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, 2021, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2026, totaled $1 billion ($450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 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, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2021 2020 2021 2020 2021 2020 Amount outstanding $515 $389 $— $— $236 $257 Weighted average interest rates 0.2% 0.2% N/A N/A 0.2% 0.1% Available credit facility capacity $485 $611 $250 $250 $64 $43 Alliant Energy IPL WPL For the year ended 2021 2020 2021 2020 2021 2020 Maximum amount outstanding (based on daily outstanding balances) $648 $495 $19 $8 $320 $266 Average amount outstanding (based on daily outstanding balances) $459 $292 $— $— $172 $117 Weighted average interest rates 0.2% 0.7% 0.2% 0.5% 0.1% 0.7% 2021 2020 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 (b) 300 300 — — — — 3,675 3,675 — 3,375 3,375 — Debentures (a): 2.25%, due 2022 250 — 250 250 — 250 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 (c) 300 — 300 — — — 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 2,450 — 2,450 2,150 — 2,150 Other: AEF term loan credit agreement through March 2022, 1% at December 31, 2021 (with Alliant Energy as guarantor) 300 — — 300 — — Corporate Services 3.45% senior notes, due 2022 (a) 75 — — 75 — — AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 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 — — Sheboygan Power, LLC 5.06% senior secured notes, due 2022 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 24 — — 31 — — Other, 1% at December 31, 2021, due 2022 to 2025 1 — — 2 — — 1,300 — — 1,308 — — Subtotal 7,425 3,675 2,450 6,833 3,375 2,150 Current maturities (633) — (250) (8) — — Unamortized debt issuance costs (42) (23) (15) (41) (22) (14) Unamortized debt (discount) and premium, net (15) (9) (6) (15) (8) (6) Long-term debt, net (d) $6,735 $3,643 $2,179 $6,769 $3,345 $2,130 (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 November 2021, IPL issued $300 million of 3.1% senior debentures due 2051. The net proceeds from the issuance were used by IPL to retire its cumulative preferred stock in 2021 and for general corporate purposes. (c) In September 2021, WPL issued $300 million of 1.95% debentures due 2031. The debentures were issued as green bonds, and an amount in excess of the net proceeds was disbursed for the construction and development of WPL’s wind and solar EGUs. (d) There were no significant sinking fund requirements related to the outstanding long-term debt. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2021, long-term debt maturities for 2022 through 2026 were as follows (in millions): 2022 2023 2024 2025 2026 IPL $— $— $500 $300 $— WPL 250 — — — — Corporate Services 75 — — — — AEF 308 408 9 — 200 Alliant Energy $633 $408 $509 $300 $200 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, 2021, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2026, totaled $1 billion ($450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 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, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2021 2020 2021 2020 2021 2020 Amount outstanding $515 $389 $— $— $236 $257 Weighted average interest rates 0.2% 0.2% N/A N/A 0.2% 0.1% Available credit facility capacity $485 $611 $250 $250 $64 $43 Alliant Energy IPL WPL For the year ended 2021 2020 2021 2020 2021 2020 Maximum amount outstanding (based on daily outstanding balances) $648 $495 $19 $8 $320 $266 Average amount outstanding (based on daily outstanding balances) $459 $292 $— $— $172 $117 Weighted average interest rates 0.2% 0.7% 0.2% 0.5% 0.1% 0.7% 2021 2020 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 (b) 300 300 — — — — 3,675 3,675 — 3,375 3,375 — Debentures (a): 2.25%, due 2022 250 — 250 250 — 250 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 (c) 300 — 300 — — — 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 2,450 — 2,450 2,150 — 2,150 Other: AEF term loan credit agreement through March 2022, 1% at December 31, 2021 (with Alliant Energy as guarantor) 300 — — 300 — — Corporate Services 3.45% senior notes, due 2022 (a) 75 — — 75 — — AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 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 — — Sheboygan Power, LLC 5.06% senior secured notes, due 2022 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 24 — — 31 — — Other, 1% at December 31, 2021, due 2022 to 2025 1 — — 2 — — 1,300 — — 1,308 — — Subtotal 7,425 3,675 2,450 6,833 3,375 2,150 Current maturities (633) — (250) (8) — — Unamortized debt issuance costs (42) (23) (15) (41) (22) (14) Unamortized debt (discount) and premium, net (15) (9) (6) (15) (8) (6) Long-term debt, net (d) $6,735 $3,643 $2,179 $6,769 $3,345 $2,130 (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 November 2021, IPL issued $300 million of 3.1% senior debentures due 2051. The net proceeds from the issuance were used by IPL to retire its cumulative preferred stock in 2021 and for general corporate purposes. (c) In September 2021, WPL issued $300 million of 1.95% debentures due 2031. The debentures were issued as green bonds, and an amount in excess of the net proceeds was disbursed for the construction and development of WPL’s wind and solar EGUs. (d) There were no significant sinking fund requirements related to the outstanding long-term debt. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2021, long-term debt maturities for 2022 through 2026 were as follows (in millions): 2022 2023 2024 2025 2026 IPL $— $— $500 $300 $— WPL 250 — — — — Corporate Services 75 — — — — AEF 308 408 9 — 200 Alliant Energy $633 $408 $509 $300 $200 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, 2021, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2026, totaled $1 billion ($450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 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, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2021 2020 2021 2020 2021 2020 Amount outstanding $515 $389 $— $— $236 $257 Weighted average interest rates 0.2% 0.2% N/A N/A 0.2% 0.1% Available credit facility capacity $485 $611 $250 $250 $64 $43 Alliant Energy IPL WPL For the year ended 2021 2020 2021 2020 2021 2020 Maximum amount outstanding (based on daily outstanding balances) $648 $495 $19 $8 $320 $266 Average amount outstanding (based on daily outstanding balances) $459 $292 $— $— $172 $117 Weighted average interest rates 0.2% 0.7% 0.2% 0.5% 0.1% 0.7% 2021 2020 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 (b) 300 300 — — — — 3,675 3,675 — 3,375 3,375 — Debentures (a): 2.25%, due 2022 250 — 250 250 — 250 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 (c) 300 — 300 — — — 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 2,450 — 2,450 2,150 — 2,150 Other: AEF term loan credit agreement through March 2022, 1% at December 31, 2021 (with Alliant Energy as guarantor) 300 — — 300 — — Corporate Services 3.45% senior notes, due 2022 (a) 75 — — 75 — — AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 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 — — Sheboygan Power, LLC 5.06% senior secured notes, due 2022 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 24 — — 31 — — Other, 1% at December 31, 2021, due 2022 to 2025 1 — — 2 — — 1,300 — — 1,308 — — Subtotal 7,425 3,675 2,450 6,833 3,375 2,150 Current maturities (633) — (250) (8) — — Unamortized debt issuance costs (42) (23) (15) (41) (22) (14) Unamortized debt (discount) and premium, net (15) (9) (6) (15) (8) (6) Long-term debt, net (d) $6,735 $3,643 $2,179 $6,769 $3,345 $2,130 (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 November 2021, IPL issued $300 million of 3.1% senior debentures due 2051. The net proceeds from the issuance were used by IPL to retire its cumulative preferred stock in 2021 and for general corporate purposes. (c) In September 2021, WPL issued $300 million of 1.95% debentures due 2031. The debentures were issued as green bonds, and an amount in excess of the net proceeds was disbursed for the construction and development of WPL’s wind and solar EGUs. (d) There were no significant sinking fund requirements related to the outstanding long-term debt. Five-Year Schedule of Long-term Debt Maturities - At December 31, 2021, long-term debt maturities for 2022 through 2026 were as follows (in millions): 2022 2023 2024 2025 2026 IPL $— $— $500 $300 $— WPL 250 — — — — Corporate Services 75 — — — — AEF 308 408 9 — 200 Alliant Energy $633 $408 $509 $300 $200 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, 2021
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, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 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 is 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. 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): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13 Expected Maturities - As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
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, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 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 is 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. 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): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13 Expected Maturities - As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
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, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 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 is 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. 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): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13 Expected Maturities - As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
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, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 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 is 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. 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): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13 Expected Maturities - As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
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, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 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 is 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. 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): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13 Expected Maturities - As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53

Revenues

Revenues	12 Months Ended
	Dec. 31, 2021
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 sells 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, which began operations in 2021. Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Electric Utility: Retail - residential $1,115 $1,093 $1,092 $620 $602 $601 $495 $491 $491 Retail - commercial 763 718 770 508 474 510 255 244 260 Retail - industrial 893 841 889 505 488 504 388 353 385 Wholesale 187 168 177 57 57 64 130 111 113 Bulk power and other 123 100 136 62 74 102 61 26 34 Total Electric Utility 3,081 2,920 3,064 1,752 1,695 1,781 1,329 1,225 1,283 Gas Utility: Retail - residential 257 214 259 146 116 149 111 98 110 Retail - commercial 139 107 133 79 59 75 60 48 58 Retail - industrial 17 12 16 12 8 12 5 4 4 Transportation/other 43 40 47 28 25 28 15 15 19 Total Gas Utility 456 373 455 265 208 264 191 165 191 Other Utility: Steam 36 36 37 36 36 37 — — — Other utility 13 13 9 10 8 7 3 5 2 Total Other Utility 49 49 46 46 44 44 3 5 2 Non-Utility and Other: Travero and other 83 74 83 — — — — — — Total Non-Utility and Other 83 74 83 — — — — — — Total revenues $3,669 $3,416 $3,648 $2,063 $1,947 $2,089 $1,523 $1,395 $1,476
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 sells 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, which began operations in 2021. Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Electric Utility: Retail - residential $1,115 $1,093 $1,092 $620 $602 $601 $495 $491 $491 Retail - commercial 763 718 770 508 474 510 255 244 260 Retail - industrial 893 841 889 505 488 504 388 353 385 Wholesale 187 168 177 57 57 64 130 111 113 Bulk power and other 123 100 136 62 74 102 61 26 34 Total Electric Utility 3,081 2,920 3,064 1,752 1,695 1,781 1,329 1,225 1,283 Gas Utility: Retail - residential 257 214 259 146 116 149 111 98 110 Retail - commercial 139 107 133 79 59 75 60 48 58 Retail - industrial 17 12 16 12 8 12 5 4 4 Transportation/other 43 40 47 28 25 28 15 15 19 Total Gas Utility 456 373 455 265 208 264 191 165 191 Other Utility: Steam 36 36 37 36 36 37 — — — Other utility 13 13 9 10 8 7 3 5 2 Total Other Utility 49 49 46 46 44 44 3 5 2 Non-Utility and Other: Travero and other 83 74 83 — — — — — — Total Non-Utility and Other 83 74 83 — — — — — — Total revenues $3,669 $3,416 $3,648 $2,063 $1,947 $2,089 $1,523 $1,395 $1,476
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 sells 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, which began operations in 2021. Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions): Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Electric Utility: Retail - residential $1,115 $1,093 $1,092 $620 $602 $601 $495 $491 $491 Retail - commercial 763 718 770 508 474 510 255 244 260 Retail - industrial 893 841 889 505 488 504 388 353 385 Wholesale 187 168 177 57 57 64 130 111 113 Bulk power and other 123 100 136 62 74 102 61 26 34 Total Electric Utility 3,081 2,920 3,064 1,752 1,695 1,781 1,329 1,225 1,283 Gas Utility: Retail - residential 257 214 259 146 116 149 111 98 110 Retail - commercial 139 107 133 79 59 75 60 48 58 Retail - industrial 17 12 16 12 8 12 5 4 4 Transportation/other 43 40 47 28 25 28 15 15 19 Total Gas Utility 456 373 455 265 208 264 191 165 191 Other Utility: Steam 36 36 37 36 36 37 — — — Other utility 13 13 9 10 8 7 3 5 2 Total Other Utility 49 49 46 46 44 44 3 5 2 Non-Utility and Other: Travero and other 83 74 83 — — — — — — Total Non-Utility and Other 83 74 83 — — — — — — Total revenues $3,669 $3,416 $3,648 $2,063 $1,947 $2,089 $1,523 $1,395 $1,476

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Current tax expense (benefit): Federal $1 $1 ($7) ($21) $6 ($11) $22 ($11) $12 State 3 8 24 (1) (1) 24 6 7 13 IPL’s tax benefit riders — — (4) — — (4) — — — Deferred tax expense (benefit): Federal 9 22 70 73 30 26 (75) (9) 31 State 15 8 42 — (2) 31 11 10 6 Production tax credits (101) (95) (55) (87) (80) (42) (14) (15) (13) Investment tax credits (1) (1) (1) — — — (1) (1) — ($74) ($57) $69 ($36) ($47) $24 ($51) ($19) $49 Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes. Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Statutory federal income tax rate 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % State income taxes, net of federal benefits 2 2 7 (1) (1) 8 6 6 6 Amortization of excess deferred taxes (Refer to Note 2 ) (18) (13) (1) (4) (5) — (43) (26) (2) Production tax credits (17) (17) (9) (27) (28) (13) (6) (7) (5) Effect of rate-making on property-related differences (1) (3) (6) (2) (4) (10) (1) (2) (3) Adjustment for prior period taxes 1 1 1 2 1 3 — — — IPL’s tax benefit riders — — (1) — — (1) — — — Other items, net — (1) (1) — — — (1) — — Overall income tax rate (12 %) (10 %) 11 % (11 %) (16 %) 8 % (24 %) (8 %) 17 % 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 2021 2020 2021 2020 2021 2020 Deferred tax liabilities: Property $2,389 $2,232 $1,416 $1,312 $913 $854 ATC Holdings 123 116 — — — — Other 111 101 76 83 50 41 Total deferred tax liabilities 2,623 2,449 1,492 1,395 963 895 Deferred tax assets: Federal credit carryforwards 560 454 345 258 192 175 Net operating losses carryforwards - federal 39 77 36 71 — 1 Net operating losses carryforwards - state 38 37 3 1 — — Other 65 73 25 30 18 18 Subtotal deferred tax assets 702 641 409 360 210 194 Valuation allowances (6) (6) — — — (1) Total deferred tax assets 696 635 409 360 210 193 Total deferred tax liabilities, net $1,927 $1,814 $1,083 $1,035 $753 $702 Carryforwards - At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $186 $172 $1 State net operating losses 2022-2041 619 28 2 Federal tax credits 2022-2041 560 345 192 Valuation Allowances - Alliant Energy currently expects its federal net operating losses carryforwards will not be fully utilized until 2023. Because taxable income must be reduced by federal net operating losses carryforwards prior to utilizing federal tax credit carryforwards, Alliant Energy currently does not expect to utilize 2002 vintage federal credit carryforwards prior to their expiration in 2022, resulting in valuation allowances as of December 31, 2021. Uncertain Tax Positions - At December 31, 2021, 2020 and 2019, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2021, 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) 2018 - 2020 Consolidated Iowa income tax returns (b) 2018 - 2020 Wisconsin combined tax returns (c) 2017 - 2020 (a) The 2018 and 2019 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.
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Current tax expense (benefit): Federal $1 $1 ($7) ($21) $6 ($11) $22 ($11) $12 State 3 8 24 (1) (1) 24 6 7 13 IPL’s tax benefit riders — — (4) — — (4) — — — Deferred tax expense (benefit): Federal 9 22 70 73 30 26 (75) (9) 31 State 15 8 42 — (2) 31 11 10 6 Production tax credits (101) (95) (55) (87) (80) (42) (14) (15) (13) Investment tax credits (1) (1) (1) — — — (1) (1) — ($74) ($57) $69 ($36) ($47) $24 ($51) ($19) $49 Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes. Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Statutory federal income tax rate 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % State income taxes, net of federal benefits 2 2 7 (1) (1) 8 6 6 6 Amortization of excess deferred taxes (Refer to Note 2 ) (18) (13) (1) (4) (5) — (43) (26) (2) Production tax credits (17) (17) (9) (27) (28) (13) (6) (7) (5) Effect of rate-making on property-related differences (1) (3) (6) (2) (4) (10) (1) (2) (3) Adjustment for prior period taxes 1 1 1 2 1 3 — — — IPL’s tax benefit riders — — (1) — — (1) — — — Other items, net — (1) (1) — — — (1) — — Overall income tax rate (12 %) (10 %) 11 % (11 %) (16 %) 8 % (24 %) (8 %) 17 % 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 2021 2020 2021 2020 2021 2020 Deferred tax liabilities: Property $2,389 $2,232 $1,416 $1,312 $913 $854 ATC Holdings 123 116 — — — — Other 111 101 76 83 50 41 Total deferred tax liabilities 2,623 2,449 1,492 1,395 963 895 Deferred tax assets: Federal credit carryforwards 560 454 345 258 192 175 Net operating losses carryforwards - federal 39 77 36 71 — 1 Net operating losses carryforwards - state 38 37 3 1 — — Other 65 73 25 30 18 18 Subtotal deferred tax assets 702 641 409 360 210 194 Valuation allowances (6) (6) — — — (1) Total deferred tax assets 696 635 409 360 210 193 Total deferred tax liabilities, net $1,927 $1,814 $1,083 $1,035 $753 $702 Carryforwards - At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $186 $172 $1 State net operating losses 2022-2041 619 28 2 Federal tax credits 2022-2041 560 345 192 Valuation Allowances - Alliant Energy currently expects its federal net operating losses carryforwards will not be fully utilized until 2023. Because taxable income must be reduced by federal net operating losses carryforwards prior to utilizing federal tax credit carryforwards, Alliant Energy currently does not expect to utilize 2002 vintage federal credit carryforwards prior to their expiration in 2022, resulting in valuation allowances as of December 31, 2021. Uncertain Tax Positions - At December 31, 2021, 2020 and 2019, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2021, 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) 2018 - 2020 Consolidated Iowa income tax returns (b) 2018 - 2020 Wisconsin combined tax returns (c) 2017 - 2020 (a) The 2018 and 2019 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.
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Current tax expense (benefit): Federal $1 $1 ($7) ($21) $6 ($11) $22 ($11) $12 State 3 8 24 (1) (1) 24 6 7 13 IPL’s tax benefit riders — — (4) — — (4) — — — Deferred tax expense (benefit): Federal 9 22 70 73 30 26 (75) (9) 31 State 15 8 42 — (2) 31 11 10 6 Production tax credits (101) (95) (55) (87) (80) (42) (14) (15) (13) Investment tax credits (1) (1) (1) — — — (1) (1) — ($74) ($57) $69 ($36) ($47) $24 ($51) ($19) $49 Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes. Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Statutory federal income tax rate 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % State income taxes, net of federal benefits 2 2 7 (1) (1) 8 6 6 6 Amortization of excess deferred taxes (Refer to Note 2 ) (18) (13) (1) (4) (5) — (43) (26) (2) Production tax credits (17) (17) (9) (27) (28) (13) (6) (7) (5) Effect of rate-making on property-related differences (1) (3) (6) (2) (4) (10) (1) (2) (3) Adjustment for prior period taxes 1 1 1 2 1 3 — — — IPL’s tax benefit riders — — (1) — — (1) — — — Other items, net — (1) (1) — — — (1) — — Overall income tax rate (12 %) (10 %) 11 % (11 %) (16 %) 8 % (24 %) (8 %) 17 % 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 2021 2020 2021 2020 2021 2020 Deferred tax liabilities: Property $2,389 $2,232 $1,416 $1,312 $913 $854 ATC Holdings 123 116 — — — — Other 111 101 76 83 50 41 Total deferred tax liabilities 2,623 2,449 1,492 1,395 963 895 Deferred tax assets: Federal credit carryforwards 560 454 345 258 192 175 Net operating losses carryforwards - federal 39 77 36 71 — 1 Net operating losses carryforwards - state 38 37 3 1 — — Other 65 73 25 30 18 18 Subtotal deferred tax assets 702 641 409 360 210 194 Valuation allowances (6) (6) — — — (1) Total deferred tax assets 696 635 409 360 210 193 Total deferred tax liabilities, net $1,927 $1,814 $1,083 $1,035 $753 $702 Carryforwards - At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $186 $172 $1 State net operating losses 2022-2041 619 28 2 Federal tax credits 2022-2041 560 345 192 Valuation Allowances - Alliant Energy currently expects its federal net operating losses carryforwards will not be fully utilized until 2023. Because taxable income must be reduced by federal net operating losses carryforwards prior to utilizing federal tax credit carryforwards, Alliant Energy currently does not expect to utilize 2002 vintage federal credit carryforwards prior to their expiration in 2022, resulting in valuation allowances as of December 31, 2021. Uncertain Tax Positions - At December 31, 2021, 2020 and 2019, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2021, 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) 2018 - 2020 Consolidated Iowa income tax returns (b) 2018 - 2020 Wisconsin combined tax returns (c) 2017 - 2020 (a) The 2018 and 2019 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.

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Discount rate for net periodic cost 2.57% 3.48% 4.34% 2.31% 3.40% 4.24% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.80% 4.50% 5.44% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 4.18% 4.76% 5.52% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.65% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Discount rate for net periodic cost 2.61% 3.51% 4.35% 2.28% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 5.10% 4.50% 5.60% Rate of compensation increase 3.30% 3.65% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Discount rate for net periodic cost 2.64% 3.50% 4.35% 2.27% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.02% 3.28% 3.81% Rate of compensation increase 3.30% 3.65% 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 2020 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. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $11 $11 $10 $4 $3 $3 Interest cost 34 43 50 5 7 9 Expected return on plan assets (a) (69) (70) (60) (5) (5) (5) Amortization of prior service credit (b) — — (1) — — — Amortization of actuarial loss (c) 39 34 36 5 3 3 Settlement losses (d) — 12 — — — — $15 $30 $35 $9 $8 $10 IPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $7 $7 $6 $1 $1 $1 Interest cost 16 20 23 2 3 3 Expected return on plan assets (a) (32) (33) (28) (3) (4) (4) Amortization of actuarial loss (c) 17 15 15 2 1 2 Settlement losses (d) — 7 — — — — $8 $16 $16 $2 $1 $2 WPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $4 $4 $3 $1 $2 $1 Interest cost 15 19 21 2 3 3 Expected return on plan assets (a) (31) (31) (26) — (1) (1) Amortization of prior service credit (b) — — — — (1) — Amortization of actuarial loss (c) 19 16 18 2 2 2 $7 $8 $16 $5 $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 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 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $1,351 $1,280 $227 $214 Service cost 11 11 4 3 Interest cost 34 43 5 7 Plan participants’ contributions — — 5 4 Actuarial (gain) loss (46) 132 (12) 18 Gross benefits paid (99) (115) (19) (19) Net benefit obligation at December 31 1,251 1,351 210 227 Change in plan assets: Fair value of plan assets at January 1 984 931 108 105 Actual return on plan assets 87 108 4 11 Employer contributions 39 60 8 7 Plan participants’ contributions — — 5 4 Gross benefits paid (99) (115) (19) (19) Fair value of plan assets at December 31 1,011 984 106 108 Under funded status at December 31 ($240) ($367) ($104) ($119) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $13 $8 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (238) (365) (109) (119) Net amounts recognized at December 31 ($240) ($367) ($104) ($119) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $429 $533 $38 $54 Prior service credit (4) (5) (1) (1) $425 $528 $37 $53 Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $615 $581 $91 $86 Service cost 7 7 1 1 Interest cost 16 20 2 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss (23) 60 (4) 8 Gross benefits paid (48) (53) (8) (8) Net benefit obligation at December 31 567 615 84 91 Change in plan assets: Fair value of plan assets at January 1 453 436 74 72 Actual return on plan assets 40 51 4 7 Employer contributions 17 19 2 2 Plan participants’ contributions — — 2 1 Gross benefits paid (48) (53) (8) (8) Fair value of plan assets at December 31 462 453 74 74 Under funded status at December 31 ($105) ($162) ($10) ($17) Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $10 $4 Current liabilities — (1) (2) (2) Pension and other benefit obligations (105) (161) (18) (19) Net amounts recognized at December 31 ($105) ($162) ($10) ($17) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $180 $228 $13 $20 Prior service credit (1) (1) — — $179 $227 $13 $20 Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $588 $550 $89 $85 Service cost 4 4 1 2 Interest cost 15 19 2 3 Plan participants’ contributions — — 2 2 Actuarial (gain) loss (18) 55 (5) 5 Gross benefits paid (43) (40) (8) (8) Net benefit obligation at December 31 546 588 81 89 Change in plan assets: Fair value of plan assets at January 1 436 406 18 17 Actual return on plan assets 39 48 — 2 Employer contributions 18 22 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (43) (40) (8) (8) Fair value of plan assets at December 31 450 436 17 18 Under funded status at December 31 ($96) ($152) ($64) ($71) Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (6) (6) Pension and other benefit obligations (96) (152) (61) (68) Net amounts recognized at December 31 ($96) ($152) ($64) ($71) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $188 $233 $18 $25 Prior service credit (1) (1) (1) (1) $187 $232 $17 $24 Actuarial gains related to benefit obligations in 2021 for defined benefit pension and OPEB plans were primarily due to increases in the discount rates. Actuarial losses related to benefit obligations in 2020 for defined benefit pension and OPEB plans were primarily due to decreases in the discount rates, partially offset by the impact of updated mortality projection tables. 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 2021 2020 2021 2020 Accumulated benefit obligations $1,214 $1,305 $210 $227 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 1,214 1,305 210 227 Fair value of plan assets 1,011 984 106 108 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 1,251 1,351 N/A N/A Fair value of plan assets 1,011 984 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Accumulated benefit obligations $546 $589 $84 $91 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 546 589 84 91 Fair value of plan assets 462 453 74 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 567 615 N/A N/A Fair value of plan assets 462 453 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Accumulated benefit obligations $532 $573 $81 $89 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 532 573 81 89 Fair value of plan assets 450 436 17 18 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 546 588 N/A N/A Fair value of plan assets 450 436 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 2021 2020 2021 2020 Regulatory assets $35 $44 $30 $34 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2022 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $2 $— $— 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 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $85 $83 $82 $82 $83 $387 OPEB 18 17 17 17 16 71 $103 $100 $99 $99 $99 $458 IPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $41 $40 $39 $39 $38 $174 OPEB 7 7 7 7 7 28 $48 $47 $46 $46 $45 $202 WPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $37 $36 $35 $35 $34 $163 OPEB 7 7 7 7 6 27 $44 $43 $42 $42 $40 $190 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. At December 31, 2021, 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% 3% Equity securities - U.S. 14% - 54% 34% Equity securities - international 11% - 31% 21% Global asset securities 5% - 15% 9% Fixed income securities 25% - 45% 33% 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, 2021, 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 fixed income securities consisting of 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): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $35 $— $35 $— $46 $— $46 $— Equity securities - U.S. 256 256 — — 182 182 — — Equity securities - international — — — — 151 151 — — Global asset securities 52 52 — — 45 45 — — Fixed income securities 191 47 144 — 134 56 78 — Total assets in fair value hierarchy 534 $355 $179 $— 558 $434 $124 $— Assets measured at net asset value 477 426 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) (1) (1) Total pension plan assets $1,011 $984 2021 2020 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $21 $— $21 $— Equity securities - U.S. 117 117 — — 84 84 — — Equity securities - international — — — — 69 69 — — Global asset securities 24 24 — — 21 21 — — Fixed income securities 87 21 66 — 62 26 36 — Total assets in fair value hierarchy 244 $162 $82 $— 257 $200 $57 $— Assets measured at net asset value 218 196 Total pension plan assets $462 $453 2021 2020 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $20 $— $20 $— Equity securities - U.S. 114 114 — — 81 81 — — Equity securities - international — — — — 67 67 — — Global asset securities 23 23 — — 20 20 — — Fixed income securities 85 21 64 — 59 25 34 — Total assets in fair value hierarchy 238 $158 $80 $— 247 $193 $54 $— Assets measured at net asset value 212 189 Total pension plan assets $450 $436 At December 31, the fair values of OPEB plan assets were as follows (in millions): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $5 $— $5 $— $2 $— $2 $— Equity securities - U.S. 11 11 — — 4 4 — — Equity securities - international — — — — 3 3 — — Global asset securities 1 1 — — — — — — Fixed income securities 60 58 2 — 72 71 1 — Total assets in fair value hierarchy 77 $70 $7 $— 81 $78 $3 $— Assets measured at net asset value 29 27 Total OPEB plan assets $106 $108 2021 2020 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. 8 8 — — — — — — Fixed income securities 42 42 — — 51 51 — — Total assets in fair value hierarchy 51 $50 $1 $— 52 $51 $1 $— Assets measured at net asset value 23 22 Total OPEB plan assets $74 $74 2021 2020 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 — — — — — — Fixed income securities 15 15 — — 18 18 — — Total OPEB plan assets $17 $16 $1 $— $18 $18 $— $— 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, 2021 and 2020. 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 9% and 9% of total assets in the 401(k) savings plans at December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 401(k) costs $26 $25 $25 $13 $13 $13 $12 $12 $12 Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Compensation expense $14 $16 $26 $8 $9 $15 $6 $6 $10 Income tax benefits 4 4 7 2 2 4 2 2 3 As of December 31, 2021, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $5 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, 2021, 653,956 shares were included in the calculation of diluted EPS related to the nonvested equity awards. Performance Shares - Equity Awards - Payouts of 2021, 2020 and 2019 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 granted in 2021, 2020 and 2019 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 2021, 2020 and 2019 performance shares activity, with amounts representing the target number of awards, was as follows: 2021 2020 2019 Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Nonvested awards, January 1 129,156 $54.63 74,193 $47.44 — $— Granted 73,112 46.19 56,204 64.04 91,816 47.23 Forfeited (5,839) 51.07 (1,241) 50.94 (17,623) 46.35 Nonvested awards, December 31 196,429 51.59 129,156 54.63 74,193 47.44 Performance Shares and Performance Units - Liability Awards - Payouts of performance shares granted prior to 2019 under the Amended and Restated 2010 OIP and performance units granted prior to 2019 under the DLIP to key employees were contingent upon achievement over three-year periods of specified performance criteria, which was total shareowner return relative to an investor-owned utility peer group. Performance shares granted prior to 2019 were able to be paid out in shares of Alliant Energy common stock, cash or a combination of cash and stock. Performance units granted prior to 2019 were paid out in cash. Alliant Energy assumed it would make future payouts of its performance shares granted prior to 2019 and performance units in cash; therefore, these performance shares and performance units were accounted for as liability awards. The fair value of each performance share and performance unit accounted for as a liability award was based on the closing market price of one share of Alliant Energy common stock at the end of the performance period. The actual payout for performance shares and performance units was dependent upon actual performance and may range from zero to 200% of the target number of awards. Compensation expense for these performance shares and performance units was recorded ratably over the performance period based on the fair value of the awards at each reporting period. A summary of these performance shares and performance units activity, with amounts representing the target number of awards, was as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 Nonvested awards, January 1 68,307 131,872 203,188 16,801 34,574 57,761 Vested (68,307) (63,565) (66,322) (16,801) (16,661) (20,131) Forfeited — — (4,994) — (1,112) (3,056) Nonvested awards, December 31 — 68,307 131,872 — 16,801 34,574 Vested Awards - Certain performance shares and performance units vested, resulting in payouts (a combination of cash and common stock for the performance shares and cash only for the performance units) as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 2018 Grant 2017 Grant 2016 Grant 2018 Grant 2017 Grant 2016 Grant Performance awards vested 68,307 63,565 66,322 16,801 16,661 20,131 Percentage of target number of performance awards 172.5% 155.0% 142.5% 172.5% 155.0% 142.5% Aggregate payout value (in millions) $7 $6 $4 $2 $2 $1 Payout - cash (in millions) $5 $5 $4 $2 $2 $1 Payout - common stock shares issued 13,644 9,543 6,447 N/A N/A N/A Restricted Stock Units - Equity Awards - Payouts of 2021, 2020 and 2019 restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock units granted in 2021, 2020 and 2019 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 2021, 2020 and 2019 restricted stock units activity was as follows: 2021 2020 2019 Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Nonvested units, January 1 146,549 $51.54 89,281 $46.04 — $— Granted 80,152 48.65 61,056 59.42 105,348 45.98 Forfeited (8,882) 49.84 (3,788) 49.01 (16,067) 45.63 Nonvested units, December 31 217,819 50.54 146,549 51.54 89,281 46.04 Restricted Stock Units - Liability Awards - Payouts of restricted stock units granted prior to 2019 were based on the expiration of a three-year time-vesting period and were able to be paid out in shares of Alliant Energy common stock, cash or a combination of cash and stock. Alliant Energy assumed it would make future payouts of its restricted stock units granted prior to 2019 in cash; therefore, restricted stock units granted prior to 2019 were accounted for as liability awards. The fair value of each restricted stock unit granted prior to 2019 was based on the closing market price of one share of Alliant Energy common stock at the end of the time-vesting period. Compensation expense was recorded ratably over the performance period based on the fair value of the awards at each reporting period. A summary of the restricted stock units granted prior to 2019 activity was as follows: 2021 2020 2019 Nonvested units, January 1 58,550 113,033 174,163 Vested (58,550) (54,483) (56,849) Forfeited — — (4,281) Nonvested units, December 31 — 58,550 113,033 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. 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. 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: 2021 2020 2019 Units Weighted Average Units Weighted Average Units Weighted Average Nonvested units, January 1 197,463 $47.31 206,065 $41.50 203,188 $37.23 Granted 73,112 48.66 56,204 59.37 91,816 46.10 Vested (68,307) 38.60 (63,565) 39.12 (66,322) 33.93 Forfeited (5,839) 50.46 (1,241) 49.25 (22,617) 44.00 Nonvested units, December 31 196,429 50.74 197,463 47.31 206,065 41.50 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): 2021 2020 Carrying value $12 $11 Fair market value 24 20 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, 2021 and 2020, the carrying value of Alliant Energy’s deferred compensation obligations for participants’ interest, equity and mutual fund accounts, which approximates fair market value, was $22 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 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Discount rate for net periodic cost 2.57% 3.48% 4.34% 2.31% 3.40% 4.24% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.80% 4.50% 5.44% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 4.18% 4.76% 5.52% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.65% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Discount rate for net periodic cost 2.61% 3.51% 4.35% 2.28% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 5.10% 4.50% 5.60% Rate of compensation increase 3.30% 3.65% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Discount rate for net periodic cost 2.64% 3.50% 4.35% 2.27% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.02% 3.28% 3.81% Rate of compensation increase 3.30% 3.65% 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 2020 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. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $11 $11 $10 $4 $3 $3 Interest cost 34 43 50 5 7 9 Expected return on plan assets (a) (69) (70) (60) (5) (5) (5) Amortization of prior service credit (b) — — (1) — — — Amortization of actuarial loss (c) 39 34 36 5 3 3 Settlement losses (d) — 12 — — — — $15 $30 $35 $9 $8 $10 IPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $7 $7 $6 $1 $1 $1 Interest cost 16 20 23 2 3 3 Expected return on plan assets (a) (32) (33) (28) (3) (4) (4) Amortization of actuarial loss (c) 17 15 15 2 1 2 Settlement losses (d) — 7 — — — — $8 $16 $16 $2 $1 $2 WPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $4 $4 $3 $1 $2 $1 Interest cost 15 19 21 2 3 3 Expected return on plan assets (a) (31) (31) (26) — (1) (1) Amortization of prior service credit (b) — — — — (1) — Amortization of actuarial loss (c) 19 16 18 2 2 2 $7 $8 $16 $5 $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 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 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $1,351 $1,280 $227 $214 Service cost 11 11 4 3 Interest cost 34 43 5 7 Plan participants’ contributions — — 5 4 Actuarial (gain) loss (46) 132 (12) 18 Gross benefits paid (99) (115) (19) (19) Net benefit obligation at December 31 1,251 1,351 210 227 Change in plan assets: Fair value of plan assets at January 1 984 931 108 105 Actual return on plan assets 87 108 4 11 Employer contributions 39 60 8 7 Plan participants’ contributions — — 5 4 Gross benefits paid (99) (115) (19) (19) Fair value of plan assets at December 31 1,011 984 106 108 Under funded status at December 31 ($240) ($367) ($104) ($119) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $13 $8 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (238) (365) (109) (119) Net amounts recognized at December 31 ($240) ($367) ($104) ($119) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $429 $533 $38 $54 Prior service credit (4) (5) (1) (1) $425 $528 $37 $53 Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $615 $581 $91 $86 Service cost 7 7 1 1 Interest cost 16 20 2 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss (23) 60 (4) 8 Gross benefits paid (48) (53) (8) (8) Net benefit obligation at December 31 567 615 84 91 Change in plan assets: Fair value of plan assets at January 1 453 436 74 72 Actual return on plan assets 40 51 4 7 Employer contributions 17 19 2 2 Plan participants’ contributions — — 2 1 Gross benefits paid (48) (53) (8) (8) Fair value of plan assets at December 31 462 453 74 74 Under funded status at December 31 ($105) ($162) ($10) ($17) Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $10 $4 Current liabilities — (1) (2) (2) Pension and other benefit obligations (105) (161) (18) (19) Net amounts recognized at December 31 ($105) ($162) ($10) ($17) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $180 $228 $13 $20 Prior service credit (1) (1) — — $179 $227 $13 $20 Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $588 $550 $89 $85 Service cost 4 4 1 2 Interest cost 15 19 2 3 Plan participants’ contributions — — 2 2 Actuarial (gain) loss (18) 55 (5) 5 Gross benefits paid (43) (40) (8) (8) Net benefit obligation at December 31 546 588 81 89 Change in plan assets: Fair value of plan assets at January 1 436 406 18 17 Actual return on plan assets 39 48 — 2 Employer contributions 18 22 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (43) (40) (8) (8) Fair value of plan assets at December 31 450 436 17 18 Under funded status at December 31 ($96) ($152) ($64) ($71) Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (6) (6) Pension and other benefit obligations (96) (152) (61) (68) Net amounts recognized at December 31 ($96) ($152) ($64) ($71) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $188 $233 $18 $25 Prior service credit (1) (1) (1) (1) $187 $232 $17 $24 Actuarial gains related to benefit obligations in 2021 for defined benefit pension and OPEB plans were primarily due to increases in the discount rates. Actuarial losses related to benefit obligations in 2020 for defined benefit pension and OPEB plans were primarily due to decreases in the discount rates, partially offset by the impact of updated mortality projection tables. 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 2021 2020 2021 2020 Accumulated benefit obligations $1,214 $1,305 $210 $227 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 1,214 1,305 210 227 Fair value of plan assets 1,011 984 106 108 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 1,251 1,351 N/A N/A Fair value of plan assets 1,011 984 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Accumulated benefit obligations $546 $589 $84 $91 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 546 589 84 91 Fair value of plan assets 462 453 74 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 567 615 N/A N/A Fair value of plan assets 462 453 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Accumulated benefit obligations $532 $573 $81 $89 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 532 573 81 89 Fair value of plan assets 450 436 17 18 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 546 588 N/A N/A Fair value of plan assets 450 436 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 2021 2020 2021 2020 Regulatory assets $35 $44 $30 $34 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2022 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $2 $— $— 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 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $85 $83 $82 $82 $83 $387 OPEB 18 17 17 17 16 71 $103 $100 $99 $99 $99 $458 IPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $41 $40 $39 $39 $38 $174 OPEB 7 7 7 7 7 28 $48 $47 $46 $46 $45 $202 WPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $37 $36 $35 $35 $34 $163 OPEB 7 7 7 7 6 27 $44 $43 $42 $42 $40 $190 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. At December 31, 2021, 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% 3% Equity securities - U.S. 14% - 54% 34% Equity securities - international 11% - 31% 21% Global asset securities 5% - 15% 9% Fixed income securities 25% - 45% 33% 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, 2021, 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 fixed income securities consisting of 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): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $35 $— $35 $— $46 $— $46 $— Equity securities - U.S. 256 256 — — 182 182 — — Equity securities - international — — — — 151 151 — — Global asset securities 52 52 — — 45 45 — — Fixed income securities 191 47 144 — 134 56 78 — Total assets in fair value hierarchy 534 $355 $179 $— 558 $434 $124 $— Assets measured at net asset value 477 426 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) (1) (1) Total pension plan assets $1,011 $984 2021 2020 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $21 $— $21 $— Equity securities - U.S. 117 117 — — 84 84 — — Equity securities - international — — — — 69 69 — — Global asset securities 24 24 — — 21 21 — — Fixed income securities 87 21 66 — 62 26 36 — Total assets in fair value hierarchy 244 $162 $82 $— 257 $200 $57 $— Assets measured at net asset value 218 196 Total pension plan assets $462 $453 2021 2020 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $20 $— $20 $— Equity securities - U.S. 114 114 — — 81 81 — — Equity securities - international — — — — 67 67 — — Global asset securities 23 23 — — 20 20 — — Fixed income securities 85 21 64 — 59 25 34 — Total assets in fair value hierarchy 238 $158 $80 $— 247 $193 $54 $— Assets measured at net asset value 212 189 Total pension plan assets $450 $436 At December 31, the fair values of OPEB plan assets were as follows (in millions): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $5 $— $5 $— $2 $— $2 $— Equity securities - U.S. 11 11 — — 4 4 — — Equity securities - international — — — — 3 3 — — Global asset securities 1 1 — — — — — — Fixed income securities 60 58 2 — 72 71 1 — Total assets in fair value hierarchy 77 $70 $7 $— 81 $78 $3 $— Assets measured at net asset value 29 27 Total OPEB plan assets $106 $108 2021 2020 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. 8 8 — — — — — — Fixed income securities 42 42 — — 51 51 — — Total assets in fair value hierarchy 51 $50 $1 $— 52 $51 $1 $— Assets measured at net asset value 23 22 Total OPEB plan assets $74 $74 2021 2020 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 — — — — — — Fixed income securities 15 15 — — 18 18 — — Total OPEB plan assets $17 $16 $1 $— $18 $18 $— $— 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, 2021 and 2020. 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 9% and 9% of total assets in the 401(k) savings plans at December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 401(k) costs $26 $25 $25 $13 $13 $13 $12 $12 $12 Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Compensation expense $14 $16 $26 $8 $9 $15 $6 $6 $10 Income tax benefits 4 4 7 2 2 4 2 2 3 As of December 31, 2021, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $5 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, 2021, 653,956 shares were included in the calculation of diluted EPS related to the nonvested equity awards. Performance Shares - Equity Awards - Payouts of 2021, 2020 and 2019 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 granted in 2021, 2020 and 2019 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 2021, 2020 and 2019 performance shares activity, with amounts representing the target number of awards, was as follows: 2021 2020 2019 Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Nonvested awards, January 1 129,156 $54.63 74,193 $47.44 — $— Granted 73,112 46.19 56,204 64.04 91,816 47.23 Forfeited (5,839) 51.07 (1,241) 50.94 (17,623) 46.35 Nonvested awards, December 31 196,429 51.59 129,156 54.63 74,193 47.44 Performance Shares and Performance Units - Liability Awards - Payouts of performance shares granted prior to 2019 under the Amended and Restated 2010 OIP and performance units granted prior to 2019 under the DLIP to key employees were contingent upon achievement over three-year periods of specified performance criteria, which was total shareowner return relative to an investor-owned utility peer group. Performance shares granted prior to 2019 were able to be paid out in shares of Alliant Energy common stock, cash or a combination of cash and stock. Performance units granted prior to 2019 were paid out in cash. Alliant Energy assumed it would make future payouts of its performance shares granted prior to 2019 and performance units in cash; therefore, these performance shares and performance units were accounted for as liability awards. The fair value of each performance share and performance unit accounted for as a liability award was based on the closing market price of one share of Alliant Energy common stock at the end of the performance period. The actual payout for performance shares and performance units was dependent upon actual performance and may range from zero to 200% of the target number of awards. Compensation expense for these performance shares and performance units was recorded ratably over the performance period based on the fair value of the awards at each reporting period. A summary of these performance shares and performance units activity, with amounts representing the target number of awards, was as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 Nonvested awards, January 1 68,307 131,872 203,188 16,801 34,574 57,761 Vested (68,307) (63,565) (66,322) (16,801) (16,661) (20,131) Forfeited — — (4,994) — (1,112) (3,056) Nonvested awards, December 31 — 68,307 131,872 — 16,801 34,574 Vested Awards - Certain performance shares and performance units vested, resulting in payouts (a combination of cash and common stock for the performance shares and cash only for the performance units) as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 2018 Grant 2017 Grant 2016 Grant 2018 Grant 2017 Grant 2016 Grant Performance awards vested 68,307 63,565 66,322 16,801 16,661 20,131 Percentage of target number of performance awards 172.5% 155.0% 142.5% 172.5% 155.0% 142.5% Aggregate payout value (in millions) $7 $6 $4 $2 $2 $1 Payout - cash (in millions) $5 $5 $4 $2 $2 $1 Payout - common stock shares issued 13,644 9,543 6,447 N/A N/A N/A Restricted Stock Units - Equity Awards - Payouts of 2021, 2020 and 2019 restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock units granted in 2021, 2020 and 2019 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 2021, 2020 and 2019 restricted stock units activity was as follows: 2021 2020 2019 Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Nonvested units, January 1 146,549 $51.54 89,281 $46.04 — $— Granted 80,152 48.65 61,056 59.42 105,348 45.98 Forfeited (8,882) 49.84 (3,788) 49.01 (16,067) 45.63 Nonvested units, December 31 217,819 50.54 146,549 51.54 89,281 46.04 Restricted Stock Units - Liability Awards - Payouts of restricted stock units granted prior to 2019 were based on the expiration of a three-year time-vesting period and were able to be paid out in shares of Alliant Energy common stock, cash or a combination of cash and stock. Alliant Energy assumed it would make future payouts of its restricted stock units granted prior to 2019 in cash; therefore, restricted stock units granted prior to 2019 were accounted for as liability awards. The fair value of each restricted stock unit granted prior to 2019 was based on the closing market price of one share of Alliant Energy common stock at the end of the time-vesting period. Compensation expense was recorded ratably over the performance period based on the fair value of the awards at each reporting period. A summary of the restricted stock units granted prior to 2019 activity was as follows: 2021 2020 2019 Nonvested units, January 1 58,550 113,033 174,163 Vested (58,550) (54,483) (56,849) Forfeited — — (4,281) Nonvested units, December 31 — 58,550 113,033 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. 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. 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: 2021 2020 2019 Units Weighted Average Units Weighted Average Units Weighted Average Nonvested units, January 1 197,463 $47.31 206,065 $41.50 203,188 $37.23 Granted 73,112 48.66 56,204 59.37 91,816 46.10 Vested (68,307) 38.60 (63,565) 39.12 (66,322) 33.93 Forfeited (5,839) 50.46 (1,241) 49.25 (22,617) 44.00 Nonvested units, December 31 196,429 50.74 197,463 47.31 206,065 41.50
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 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Discount rate for net periodic cost 2.57% 3.48% 4.34% 2.31% 3.40% 4.24% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.80% 4.50% 5.44% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 4.18% 4.76% 5.52% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.65% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Discount rate for net periodic cost 2.61% 3.51% 4.35% 2.28% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 5.10% 4.50% 5.60% Rate of compensation increase 3.30% 3.65% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Discount rate for net periodic cost 2.64% 3.50% 4.35% 2.27% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.02% 3.28% 3.81% Rate of compensation increase 3.30% 3.65% 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 2020 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. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $11 $11 $10 $4 $3 $3 Interest cost 34 43 50 5 7 9 Expected return on plan assets (a) (69) (70) (60) (5) (5) (5) Amortization of prior service credit (b) — — (1) — — — Amortization of actuarial loss (c) 39 34 36 5 3 3 Settlement losses (d) — 12 — — — — $15 $30 $35 $9 $8 $10 IPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $7 $7 $6 $1 $1 $1 Interest cost 16 20 23 2 3 3 Expected return on plan assets (a) (32) (33) (28) (3) (4) (4) Amortization of actuarial loss (c) 17 15 15 2 1 2 Settlement losses (d) — 7 — — — — $8 $16 $16 $2 $1 $2 WPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $4 $4 $3 $1 $2 $1 Interest cost 15 19 21 2 3 3 Expected return on plan assets (a) (31) (31) (26) — (1) (1) Amortization of prior service credit (b) — — — — (1) — Amortization of actuarial loss (c) 19 16 18 2 2 2 $7 $8 $16 $5 $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 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 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $1,351 $1,280 $227 $214 Service cost 11 11 4 3 Interest cost 34 43 5 7 Plan participants’ contributions — — 5 4 Actuarial (gain) loss (46) 132 (12) 18 Gross benefits paid (99) (115) (19) (19) Net benefit obligation at December 31 1,251 1,351 210 227 Change in plan assets: Fair value of plan assets at January 1 984 931 108 105 Actual return on plan assets 87 108 4 11 Employer contributions 39 60 8 7 Plan participants’ contributions — — 5 4 Gross benefits paid (99) (115) (19) (19) Fair value of plan assets at December 31 1,011 984 106 108 Under funded status at December 31 ($240) ($367) ($104) ($119) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $13 $8 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (238) (365) (109) (119) Net amounts recognized at December 31 ($240) ($367) ($104) ($119) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $429 $533 $38 $54 Prior service credit (4) (5) (1) (1) $425 $528 $37 $53 Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $615 $581 $91 $86 Service cost 7 7 1 1 Interest cost 16 20 2 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss (23) 60 (4) 8 Gross benefits paid (48) (53) (8) (8) Net benefit obligation at December 31 567 615 84 91 Change in plan assets: Fair value of plan assets at January 1 453 436 74 72 Actual return on plan assets 40 51 4 7 Employer contributions 17 19 2 2 Plan participants’ contributions — — 2 1 Gross benefits paid (48) (53) (8) (8) Fair value of plan assets at December 31 462 453 74 74 Under funded status at December 31 ($105) ($162) ($10) ($17) Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $10 $4 Current liabilities — (1) (2) (2) Pension and other benefit obligations (105) (161) (18) (19) Net amounts recognized at December 31 ($105) ($162) ($10) ($17) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $180 $228 $13 $20 Prior service credit (1) (1) — — $179 $227 $13 $20 Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $588 $550 $89 $85 Service cost 4 4 1 2 Interest cost 15 19 2 3 Plan participants’ contributions — — 2 2 Actuarial (gain) loss (18) 55 (5) 5 Gross benefits paid (43) (40) (8) (8) Net benefit obligation at December 31 546 588 81 89 Change in plan assets: Fair value of plan assets at January 1 436 406 18 17 Actual return on plan assets 39 48 — 2 Employer contributions 18 22 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (43) (40) (8) (8) Fair value of plan assets at December 31 450 436 17 18 Under funded status at December 31 ($96) ($152) ($64) ($71) Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (6) (6) Pension and other benefit obligations (96) (152) (61) (68) Net amounts recognized at December 31 ($96) ($152) ($64) ($71) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $188 $233 $18 $25 Prior service credit (1) (1) (1) (1) $187 $232 $17 $24 Actuarial gains related to benefit obligations in 2021 for defined benefit pension and OPEB plans were primarily due to increases in the discount rates. Actuarial losses related to benefit obligations in 2020 for defined benefit pension and OPEB plans were primarily due to decreases in the discount rates, partially offset by the impact of updated mortality projection tables. 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 2021 2020 2021 2020 Accumulated benefit obligations $1,214 $1,305 $210 $227 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 1,214 1,305 210 227 Fair value of plan assets 1,011 984 106 108 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 1,251 1,351 N/A N/A Fair value of plan assets 1,011 984 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Accumulated benefit obligations $546 $589 $84 $91 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 546 589 84 91 Fair value of plan assets 462 453 74 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 567 615 N/A N/A Fair value of plan assets 462 453 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Accumulated benefit obligations $532 $573 $81 $89 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 532 573 81 89 Fair value of plan assets 450 436 17 18 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 546 588 N/A N/A Fair value of plan assets 450 436 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 2021 2020 2021 2020 Regulatory assets $35 $44 $30 $34 Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2022 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $2 $— $— 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 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $85 $83 $82 $82 $83 $387 OPEB 18 17 17 17 16 71 $103 $100 $99 $99 $99 $458 IPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $41 $40 $39 $39 $38 $174 OPEB 7 7 7 7 7 28 $48 $47 $46 $46 $45 $202 WPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $37 $36 $35 $35 $34 $163 OPEB 7 7 7 7 6 27 $44 $43 $42 $42 $40 $190 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. At December 31, 2021, 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% 3% Equity securities - U.S. 14% - 54% 34% Equity securities - international 11% - 31% 21% Global asset securities 5% - 15% 9% Fixed income securities 25% - 45% 33% 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, 2021, 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 fixed income securities consisting of 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): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $35 $— $35 $— $46 $— $46 $— Equity securities - U.S. 256 256 — — 182 182 — — Equity securities - international — — — — 151 151 — — Global asset securities 52 52 — — 45 45 — — Fixed income securities 191 47 144 — 134 56 78 — Total assets in fair value hierarchy 534 $355 $179 $— 558 $434 $124 $— Assets measured at net asset value 477 426 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) (1) (1) Total pension plan assets $1,011 $984 2021 2020 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $21 $— $21 $— Equity securities - U.S. 117 117 — — 84 84 — — Equity securities - international — — — — 69 69 — — Global asset securities 24 24 — — 21 21 — — Fixed income securities 87 21 66 — 62 26 36 — Total assets in fair value hierarchy 244 $162 $82 $— 257 $200 $57 $— Assets measured at net asset value 218 196 Total pension plan assets $462 $453 2021 2020 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $20 $— $20 $— Equity securities - U.S. 114 114 — — 81 81 — — Equity securities - international — — — — 67 67 — — Global asset securities 23 23 — — 20 20 — — Fixed income securities 85 21 64 — 59 25 34 — Total assets in fair value hierarchy 238 $158 $80 $— 247 $193 $54 $— Assets measured at net asset value 212 189 Total pension plan assets $450 $436 At December 31, the fair values of OPEB plan assets were as follows (in millions): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $5 $— $5 $— $2 $— $2 $— Equity securities - U.S. 11 11 — — 4 4 — — Equity securities - international — — — — 3 3 — — Global asset securities 1 1 — — — — — — Fixed income securities 60 58 2 — 72 71 1 — Total assets in fair value hierarchy 77 $70 $7 $— 81 $78 $3 $— Assets measured at net asset value 29 27 Total OPEB plan assets $106 $108 2021 2020 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. 8 8 — — — — — — Fixed income securities 42 42 — — 51 51 — — Total assets in fair value hierarchy 51 $50 $1 $— 52 $51 $1 $— Assets measured at net asset value 23 22 Total OPEB plan assets $74 $74 2021 2020 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 — — — — — — Fixed income securities 15 15 — — 18 18 — — Total OPEB plan assets $17 $16 $1 $— $18 $18 $— $— 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, 2021 and 2020. 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 9% and 9% of total assets in the 401(k) savings plans at December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 401(k) costs $26 $25 $25 $13 $13 $13 $12 $12 $12 Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Compensation expense $14 $16 $26 $8 $9 $15 $6 $6 $10 Income tax benefits 4 4 7 2 2 4 2 2 3 As of December 31, 2021, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $5 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, 2021, 653,956 shares were included in the calculation of diluted EPS related to the nonvested equity awards. Performance Shares - Equity Awards - Payouts of 2021, 2020 and 2019 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 granted in 2021, 2020 and 2019 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 2021, 2020 and 2019 performance shares activity, with amounts representing the target number of awards, was as follows: 2021 2020 2019 Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Nonvested awards, January 1 129,156 $54.63 74,193 $47.44 — $— Granted 73,112 46.19 56,204 64.04 91,816 47.23 Forfeited (5,839) 51.07 (1,241) 50.94 (17,623) 46.35 Nonvested awards, December 31 196,429 51.59 129,156 54.63 74,193 47.44 Performance Shares and Performance Units - Liability Awards - Payouts of performance shares granted prior to 2019 under the Amended and Restated 2010 OIP and performance units granted prior to 2019 under the DLIP to key employees were contingent upon achievement over three-year periods of specified performance criteria, which was total shareowner return relative to an investor-owned utility peer group. Performance shares granted prior to 2019 were able to be paid out in shares of Alliant Energy common stock, cash or a combination of cash and stock. Performance units granted prior to 2019 were paid out in cash. Alliant Energy assumed it would make future payouts of its performance shares granted prior to 2019 and performance units in cash; therefore, these performance shares and performance units were accounted for as liability awards. The fair value of each performance share and performance unit accounted for as a liability award was based on the closing market price of one share of Alliant Energy common stock at the end of the performance period. The actual payout for performance shares and performance units was dependent upon actual performance and may range from zero to 200% of the target number of awards. Compensation expense for these performance shares and performance units was recorded ratably over the performance period based on the fair value of the awards at each reporting period. A summary of these performance shares and performance units activity, with amounts representing the target number of awards, was as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 Nonvested awards, January 1 68,307 131,872 203,188 16,801 34,574 57,761 Vested (68,307) (63,565) (66,322) (16,801) (16,661) (20,131) Forfeited — — (4,994) — (1,112) (3,056) Nonvested awards, December 31 — 68,307 131,872 — 16,801 34,574 Vested Awards - Certain performance shares and performance units vested, resulting in payouts (a combination of cash and common stock for the performance shares and cash only for the performance units) as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 2018 Grant 2017 Grant 2016 Grant 2018 Grant 2017 Grant 2016 Grant Performance awards vested 68,307 63,565 66,322 16,801 16,661 20,131 Percentage of target number of performance awards 172.5% 155.0% 142.5% 172.5% 155.0% 142.5% Aggregate payout value (in millions) $7 $6 $4 $2 $2 $1 Payout - cash (in millions) $5 $5 $4 $2 $2 $1 Payout - common stock shares issued 13,644 9,543 6,447 N/A N/A N/A Restricted Stock Units - Equity Awards - Payouts of 2021, 2020 and 2019 restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock units granted in 2021, 2020 and 2019 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 2021, 2020 and 2019 restricted stock units activity was as follows: 2021 2020 2019 Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Nonvested units, January 1 146,549 $51.54 89,281 $46.04 — $— Granted 80,152 48.65 61,056 59.42 105,348 45.98 Forfeited (8,882) 49.84 (3,788) 49.01 (16,067) 45.63 Nonvested units, December 31 217,819 50.54 146,549 51.54 89,281 46.04 Restricted Stock Units - Liability Awards - Payouts of restricted stock units granted prior to 2019 were based on the expiration of a three-year time-vesting period and were able to be paid out in shares of Alliant Energy common stock, cash or a combination of cash and stock. Alliant Energy assumed it would make future payouts of its restricted stock units granted prior to 2019 in cash; therefore, restricted stock units granted prior to 2019 were accounted for as liability awards. The fair value of each restricted stock unit granted prior to 2019 was based on the closing market price of one share of Alliant Energy common stock at the end of the time-vesting period. Compensation expense was recorded ratably over the performance period based on the fair value of the awards at each reporting period. A summary of the restricted stock units granted prior to 2019 activity was as follows: 2021 2020 2019 Nonvested units, January 1 58,550 113,033 174,163 Vested (58,550) (54,483) (56,849) Forfeited — — (4,281) Nonvested units, December 31 — 58,550 113,033 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. 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. 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: 2021 2020 2019 Units Weighted Average Units Weighted Average Units Weighted Average Nonvested units, January 1 197,463 $47.31 206,065 $41.50 203,188 $37.23 Granted 73,112 48.66 56,204 59.37 91,816 46.10 Vested (68,307) 38.60 (63,565) 39.12 (66,322) 33.93 Forfeited (5,839) 50.46 (1,241) 49.25 (22,617) 44.00 Nonvested units, December 31 196,429 50.74 197,463 47.31 206,065 41.50

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2021
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, coal yards, above ground storage tanks and solar generation. 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 2021 2020 2021 2020 2021 2020 Balance, January 1 $251 $196 $177 $134 $74 $62 Revisions in estimated cash flows 50 13 44 9 6 4 Liabilities settled (17) (13) (13) (9) (4) (4) Liabilities incurred 3 48 — 38 3 10 Accretion expense 7 7 5 5 2 2 Balance, December 31 $294 $251 $213 $177 $81 $74
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, coal yards, above ground storage tanks and solar generation. 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 2021 2020 2021 2020 2021 2020 Balance, January 1 $251 $196 $177 $134 $74 $62 Revisions in estimated cash flows 50 13 44 9 6 4 Liabilities settled (17) (13) (13) (9) (4) (4) Liabilities incurred 3 48 — 38 3 10 Accretion expense 7 7 5 5 2 2 Balance, December 31 $294 $251 $213 $177 $81 $74
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, coal yards, above ground storage tanks and solar generation. 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 2021 2020 2021 2020 2021 2020 Balance, January 1 $251 $196 $177 $134 $74 $62 Revisions in estimated cash flows 50 13 44 9 6 4 Liabilities settled (17) (13) (13) (9) (4) (4) Liabilities incurred 3 48 — 38 3 10 Accretion expense 7 7 5 5 2 2 Balance, December 31 $294 $251 $213 $177 $81 $74

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2021
Derivative [Line Items]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivatives - Purpose - Derivative instruments are 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) Optimize the value of natural gas pipeline capacity Natural gas physical forward contracts (IPL and WPL) Natural gas swap contracts (IPL) Manage transmission congestion costs FTRs (IPL and WPL) Manage rail transportation costs Diesel fuel swap contracts (WPL) Notional Amounts - As of December 31, 2021, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 9,135 2022 191,670 2022-2030 3,193 2022-2023 3,024 2022 IPL 2,647 2022 100,560 2022-2030 1,270 2022-2023 — — WPL 6,488 2022 91,110 2022-2030 1,923 2022-2023 3,024 2022 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 2021 2020 2021 2020 2021 2020 Current derivative assets $113 $24 $48 $20 $65 $4 Non-current derivative assets 63 10 36 9 27 1 Current derivative liabilities 8 9 4 3 4 6 Non-current derivative liabilities 1 16 — 9 1 7 In 2021, Alliant Energy’s, IPL’s and WPL’s derivative assets increased and derivative liabilities decreased primarily as a result of higher natural gas prices. Based on IPL’s and WPL’s natural gas cost recovery mechanisms, this resulted in corresponding decreases in derivative regulatory assets and increases in derivative regulatory liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2021 and 2020, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at December 31, 2021 and 2020. 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 are 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) Optimize the value of natural gas pipeline capacity Natural gas physical forward contracts (IPL and WPL) Natural gas swap contracts (IPL) Manage transmission congestion costs FTRs (IPL and WPL) Manage rail transportation costs Diesel fuel swap contracts (WPL) Notional Amounts - As of December 31, 2021, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 9,135 2022 191,670 2022-2030 3,193 2022-2023 3,024 2022 IPL 2,647 2022 100,560 2022-2030 1,270 2022-2023 — — WPL 6,488 2022 91,110 2022-2030 1,923 2022-2023 3,024 2022 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 2021 2020 2021 2020 2021 2020 Current derivative assets $113 $24 $48 $20 $65 $4 Non-current derivative assets 63 10 36 9 27 1 Current derivative liabilities 8 9 4 3 4 6 Non-current derivative liabilities 1 16 — 9 1 7 In 2021, Alliant Energy’s, IPL’s and WPL’s derivative assets increased and derivative liabilities decreased primarily as a result of higher natural gas prices. Based on IPL’s and WPL’s natural gas cost recovery mechanisms, this resulted in corresponding decreases in derivative regulatory assets and increases in derivative regulatory liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2021 and 2020, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at December 31, 2021 and 2020. 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 are 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) Optimize the value of natural gas pipeline capacity Natural gas physical forward contracts (IPL and WPL) Natural gas swap contracts (IPL) Manage transmission congestion costs FTRs (IPL and WPL) Manage rail transportation costs Diesel fuel swap contracts (WPL) Notional Amounts - As of December 31, 2021, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 9,135 2022 191,670 2022-2030 3,193 2022-2023 3,024 2022 IPL 2,647 2022 100,560 2022-2030 1,270 2022-2023 — — WPL 6,488 2022 91,110 2022-2030 1,923 2022-2023 3,024 2022 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 2021 2020 2021 2020 2021 2020 Current derivative assets $113 $24 $48 $20 $65 $4 Non-current derivative assets 63 10 36 9 27 1 Current derivative liabilities 8 9 4 3 4 6 Non-current derivative liabilities 1 16 — 9 1 7 In 2021, Alliant Energy’s, IPL’s and WPL’s derivative assets increased and derivative liabilities decreased primarily as a result of higher natural gas prices. Based on IPL’s and WPL’s natural gas cost recovery mechanisms, this resulted in corresponding decreases in derivative regulatory assets and increases in derivative regulatory liabilities on the balance sheets. Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided in the form of letters of credit or cash collateral up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2021 and 2020, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered. Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, amounts would not be materially different from gross amounts of derivative assets and derivative liabilities at December 31, 2021 and 2020. 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, 2021
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 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 176 — 146 30 176 34 — 5 29 34 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 9 — 8 1 9 25 — 25 — 25 Long-term debt (incl. current maturities) 7,368 — 8,329 1 8,330 6,777 — 8,107 2 8,109 IPL 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 84 — 65 19 84 29 — 3 26 29 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 4 — 3 1 4 12 — 12 — 12 Long-term debt 3,643 — 4,124 — 4,124 3,345 — 4,021 — 4,021 WPL 2021 2020 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $92 $— $81 $11 $92 $5 $— $2 $3 $5 Liabilities and equity: Derivatives 5 — 5 — 5 13 — 13 — 13 Long-term debt (incl. current maturities) 2,429 — 2,862 — 2,862 2,130 — 2,690 — 2,690 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 2021 2020 2021 2020 Beginning balance, January 1 $29 $21 $188 $188 Total net gains included in changes in net assets (realized/unrealized) 6 11 — — Purchases 21 14 — — Sales (1) (1) — — Settlements (a) (26) (16) 26 — Ending balance, December 31 $29 $29 $214 $188 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $6 $11 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2021 2020 2021 2020 Beginning balance, January 1 $26 $18 $188 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (3) 10 — — Purchases 16 11 — — Sales (1) (1) — — Settlements (a) (20) (12) 26 — Ending balance, December 31 $18 $26 $214 $188 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 ($3) $10 $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2021 2020 Beginning balance, January 1 $3 $3 Total net gains included in changes in net assets (realized/unrealized) 9 1 Purchases 5 3 Settlements (6) (4) Ending balance, December 31 $11 $3 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $9 $1 (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2021 $9 $20 $8 $10 $1 $10 2020 18 11 17 9 1 2
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 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 176 — 146 30 176 34 — 5 29 34 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 9 — 8 1 9 25 — 25 — 25 Long-term debt (incl. current maturities) 7,368 — 8,329 1 8,330 6,777 — 8,107 2 8,109 IPL 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 84 — 65 19 84 29 — 3 26 29 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 4 — 3 1 4 12 — 12 — 12 Long-term debt 3,643 — 4,124 — 4,124 3,345 — 4,021 — 4,021 WPL 2021 2020 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $92 $— $81 $11 $92 $5 $— $2 $3 $5 Liabilities and equity: Derivatives 5 — 5 — 5 13 — 13 — 13 Long-term debt (incl. current maturities) 2,429 — 2,862 — 2,862 2,130 — 2,690 — 2,690 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 2021 2020 2021 2020 Beginning balance, January 1 $29 $21 $188 $188 Total net gains included in changes in net assets (realized/unrealized) 6 11 — — Purchases 21 14 — — Sales (1) (1) — — Settlements (a) (26) (16) 26 — Ending balance, December 31 $29 $29 $214 $188 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $6 $11 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2021 2020 2021 2020 Beginning balance, January 1 $26 $18 $188 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (3) 10 — — Purchases 16 11 — — Sales (1) (1) — — Settlements (a) (20) (12) 26 — Ending balance, December 31 $18 $26 $214 $188 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 ($3) $10 $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2021 2020 Beginning balance, January 1 $3 $3 Total net gains included in changes in net assets (realized/unrealized) 9 1 Purchases 5 3 Settlements (6) (4) Ending balance, December 31 $11 $3 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $9 $1 (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2021 $9 $20 $8 $10 $1 $10 2020 18 11 17 9 1 2
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 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 176 — 146 30 176 34 — 5 29 34 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 9 — 8 1 9 25 — 25 — 25 Long-term debt (incl. current maturities) 7,368 — 8,329 1 8,330 6,777 — 8,107 2 8,109 IPL 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 84 — 65 19 84 29 — 3 26 29 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 4 — 3 1 4 12 — 12 — 12 Long-term debt 3,643 — 4,124 — 4,124 3,345 — 4,021 — 4,021 WPL 2021 2020 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $92 $— $81 $11 $92 $5 $— $2 $3 $5 Liabilities and equity: Derivatives 5 — 5 — 5 13 — 13 — 13 Long-term debt (incl. current maturities) 2,429 — 2,862 — 2,862 2,130 — 2,690 — 2,690 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 2021 2020 2021 2020 Beginning balance, January 1 $29 $21 $188 $188 Total net gains included in changes in net assets (realized/unrealized) 6 11 — — Purchases 21 14 — — Sales (1) (1) — — Settlements (a) (26) (16) 26 — Ending balance, December 31 $29 $29 $214 $188 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $6 $11 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2021 2020 2021 2020 Beginning balance, January 1 $26 $18 $188 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (3) 10 — — Purchases 16 11 — — Sales (1) (1) — — Settlements (a) (20) (12) 26 — Ending balance, December 31 $18 $26 $214 $188 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 ($3) $10 $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2021 2020 Beginning balance, January 1 $3 $3 Total net gains included in changes in net assets (realized/unrealized) 9 1 Purchases 5 3 Settlements (6) (4) Ending balance, December 31 $11 $3 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $9 $1 (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2021 $9 $20 $8 $10 $1 $10 2020 18 11 17 9 1 2

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2021
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, 2021, Alliant Energy’s and WPL’s minimum future commitments in 2022 for these projects were $178 million and $177 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, 2021, the related minimum future commitments were as follows (in millions): Alliant Energy 2022 2023 2024 2025 2026 Thereafter Total Natural gas $307 $196 $144 $102 $88 $175 $1,012 Coal 63 46 25 3 — — 137 Other (a) 82 14 8 5 2 25 136 $452 $256 $177 $110 $90 $200 $1,285 IPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $148 $108 $84 $52 $42 $65 $499 Coal 32 27 17 3 — — 79 Other (a) 34 4 2 2 2 23 67 $214 $139 $103 $57 $44 $88 $645 WPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $159 $88 $60 $50 $46 $110 $513 Coal 31 19 8 — — — 58 Other (a) 33 1 1 1 1 — 37 $223 $108 $69 $51 $47 $110 $608 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2021. 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, 2021, the currently known partnership obligations for the abandonment obligations are estimated at $60 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy estimates its expected loss to be a portion of the $60 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners. Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay; however, as of both December 31, 2021 and 2020, a liability of $5 million is recorded in “Other liabilities” on Alliant Energy’s balance sheets for expected credit losses related to the contingent obligations that are in the scope of these guarantees. Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $67 million as of December 31, 2021 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, 2021 and 2020. 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, 2021, 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, 2021, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $8 - $24 $6 - $18 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: 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, 2021, the related minimum future commitments were as follows (in millions): Alliant Energy 2022 2023 2024 2025 2026 Thereafter Total Natural gas $307 $196 $144 $102 $88 $175 $1,012 Coal 63 46 25 3 — — 137 Other (a) 82 14 8 5 2 25 136 $452 $256 $177 $110 $90 $200 $1,285 IPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $148 $108 $84 $52 $42 $65 $499 Coal 32 27 17 3 — — 79 Other (a) 34 4 2 2 2 23 67 $214 $139 $103 $57 $44 $88 $645 WPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $159 $88 $60 $50 $46 $110 $513 Coal 31 19 8 — — — 58 Other (a) 33 1 1 1 1 — 37 $223 $108 $69 $51 $47 $110 $608 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 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, 2021, 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, 2021, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $8 - $24 $6 - $18 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: 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, 2021, Alliant Energy’s and WPL’s minimum future commitments in 2022 for these projects were $178 million and $177 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, 2021, the related minimum future commitments were as follows (in millions): Alliant Energy 2022 2023 2024 2025 2026 Thereafter Total Natural gas $307 $196 $144 $102 $88 $175 $1,012 Coal 63 46 25 3 — — 137 Other (a) 82 14 8 5 2 25 136 $452 $256 $177 $110 $90 $200 $1,285 IPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $148 $108 $84 $52 $42 $65 $499 Coal 32 27 17 3 — — 79 Other (a) 34 4 2 2 2 23 67 $214 $139 $103 $57 $44 $88 $645 WPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $159 $88 $60 $50 $46 $110 $513 Coal 31 19 8 — — — 58 Other (a) 33 1 1 1 1 — 37 $223 $108 $69 $51 $47 $110 $608 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 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, 2021, 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, 2021, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $8 - $24 $6 - $18 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: 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, 2021
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2021 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 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 ATC Holdings, Utility Non-utility, Alliant Energy 2019 Electric Gas Other Total Parent and Other Consolidated Revenues $3,064 $455 $46 $3,565 $83 $3,648 Depreciation and amortization 513 47 3 563 4 567 Operating income 679 70 1 750 28 778 Interest expense 229 44 273 Equity income from unconsolidated investments, net (1) — — (1) (52) (53) Income tax expense (benefit) 73 (4) 69 Net income attributable to Alliant Energy common shareowners 517 40 557 Total assets 13,659 1,269 856 15,784 917 16,701 Investments in equity method subsidiaries 9 — — 9 449 458 Construction and acquisition expenditures 1,439 100 — 1,539 101 1,640 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): 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 2019 Electric Gas Other Total Revenues $1,781 $264 $44 $2,089 Depreciation and amortization 295 29 3 327 Operating income 360 39 4 403 Interest expense 127 Income taxes 24 Net income available for common stock 284 Total assets 8,075 734 468 9,277 Construction and acquisition expenditures 964 56 — 1,020 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): 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 2019 Electric Gas Other Total Revenues $1,283 $191 $2 $1,476 Depreciation and amortization 218 18 — 236 Operating income (loss) 319 31 (3) 347 Interest expense 102 Income taxes 49 Net income 233 Total assets 5,584 535 388 6,507 Construction and acquisition expenditures 475 44 — 519
IPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2021 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 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 ATC Holdings, Utility Non-utility, Alliant Energy 2019 Electric Gas Other Total Parent and Other Consolidated Revenues $3,064 $455 $46 $3,565 $83 $3,648 Depreciation and amortization 513 47 3 563 4 567 Operating income 679 70 1 750 28 778 Interest expense 229 44 273 Equity income from unconsolidated investments, net (1) — — (1) (52) (53) Income tax expense (benefit) 73 (4) 69 Net income attributable to Alliant Energy common shareowners 517 40 557 Total assets 13,659 1,269 856 15,784 917 16,701 Investments in equity method subsidiaries 9 — — 9 449 458 Construction and acquisition expenditures 1,439 100 — 1,539 101 1,640 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): 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 2019 Electric Gas Other Total Revenues $1,781 $264 $44 $2,089 Depreciation and amortization 295 29 3 327 Operating income 360 39 4 403 Interest expense 127 Income taxes 24 Net income available for common stock 284 Total assets 8,075 734 468 9,277 Construction and acquisition expenditures 964 56 — 1,020 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): 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 2019 Electric Gas Other Total Revenues $1,283 $191 $2 $1,476 Depreciation and amortization 218 18 — 236 Operating income (loss) 319 31 (3) 347 Interest expense 102 Income taxes 49 Net income 233 Total assets 5,584 535 388 6,507 Construction and acquisition expenditures 475 44 — 519
WPL [Member]
Segment Reporting Information [Line Items]
Segments Of Business	SEGMENTS OF BUSINESS Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2021 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 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 ATC Holdings, Utility Non-utility, Alliant Energy 2019 Electric Gas Other Total Parent and Other Consolidated Revenues $3,064 $455 $46 $3,565 $83 $3,648 Depreciation and amortization 513 47 3 563 4 567 Operating income 679 70 1 750 28 778 Interest expense 229 44 273 Equity income from unconsolidated investments, net (1) — — (1) (52) (53) Income tax expense (benefit) 73 (4) 69 Net income attributable to Alliant Energy common shareowners 517 40 557 Total assets 13,659 1,269 856 15,784 917 16,701 Investments in equity method subsidiaries 9 — — 9 449 458 Construction and acquisition expenditures 1,439 100 — 1,539 101 1,640 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): 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 2019 Electric Gas Other Total Revenues $1,781 $264 $44 $2,089 Depreciation and amortization 295 29 3 327 Operating income 360 39 4 403 Interest expense 127 Income taxes 24 Net income available for common stock 284 Total assets 8,075 734 468 9,277 Construction and acquisition expenditures 964 56 — 1,020 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): 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 2019 Electric Gas Other Total Revenues $1,283 $191 $2 $1,476 Depreciation and amortization 218 18 — 236 Operating income (loss) 319 31 (3) 347 Interest expense 102 Income taxes 49 Net income 233 Total assets 5,584 535 388 6,507 Construction and acquisition expenditures 475 44 — 519

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2019 2021 2020 2019 Corporate Services billings $180 $176 $185 $154 $142 $142 Sales credited 22 35 68 23 3 7 Purchases billed 441 329 331 116 108 120 As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2021 2020 IPL $110 $110 WPL 83 73 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): 2021 2020 2019 ATC billings to WPL $122 $108 $109 WPL billings to ATC 18 10 13 As of December 31, 2021 and 2020, WPL owed ATC net amounts of $10 million and $9 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 2021 2020 2019 2021 2020 2019 Corporate Services billings $180 $176 $185 $154 $142 $142 Sales credited 22 35 68 23 3 7 Purchases billed 441 329 331 116 108 120 As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2021 2020 IPL $110 $110 WPL 83 73
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 2021 2020 2019 2021 2020 2019 Corporate Services billings $180 $176 $185 $154 $142 $142 Sales credited 22 35 68 23 3 7 Purchases billed 441 329 331 116 108 120 As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2021 2020 IPL $110 $110 WPL 83 73 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): 2021 2020 2019 ATC billings to WPL $122 $108 $109 WPL billings to ATC 18 10 13 As of December 31, 2021 and 2020, WPL owed ATC net amounts of $10 million and $9 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, 2021
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 2021 2020 2019 (in millions) Operating expenses $5 $7 $2 Operating loss (5) (7) (2) Other (income) and deductions: Equity earnings from consolidated subsidiaries (664) (625) (562) Interest expense 1 2 9 Other 1 4 7 Total other (income) and deductions (662) (619) (546) Income before income taxes 657 612 544 Income tax benefit (5) (4) (15) Net income $662 $616 $559 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) December 31, CONDENSED BALANCE SHEETS 2021 2020 (in millions) ASSETS Current assets: Notes receivable from affiliated companies $16 $32 Other 5 5 Total current assets 21 37 Investments: Investments in consolidated subsidiaries 7,061 6,664 Other 2 2 Total investments 7,063 6,666 Other assets 96 88 Total assets $7,180 $6,791 LIABILITIES AND EQUITY Current liabilities: Commercial paper $279 $132 Notes payable to affiliated companies 900 937 Other 4 29 Total current liabilities 1,183 1,098 Other liabilities 2 2 Common equity: Common stock and additional paid-in capital 2,752 2,706 Retained earnings 3,255 2,996 Shares in deferred compensation trust (12) (11) Total common equity 5,995 5,691 Total liabilities and equity $7,180 $6,791 Refer to accompanying Notes to Condensed Financial Statements. ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF CASH FLOWS 2021 2020 2019 (in millions) Net cash flows from operating activities $494 $396 $305 Cash flows used for investing activities: Capital contributions to consolidated subsidiaries (295) (429) (250) Net change in notes receivable from and payable to affiliates (21) 201 8 Dividends from consolidated subsidiaries in excess of equity earnings 50 — — Net cash flows used for investing activities (266) (228) (242) Cash flows used for financing activities: Common stock dividends (403) (377) (338) Proceeds from issuance of common stock, net 28 247 390 Net change in commercial paper 147 (37) (116) Other — (1) 1 Net cash flows used for financing activities (228) (168) (63) 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 ($1) ($2) ($9) Income taxes, net 4 10 14 Refer to accompanying Notes to Condensed Financial Statements.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts And Reserves	12 Months Ended
	Dec. 31, 2021
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, 2021 $18 $12 $— $19 $11 Year ended December 31, 2020 7 25 9 23 18 Year ended December 31, 2019 10 17 2 22 7 IPL (c) Year ended December 31, 2021 $1 $6 $— $6 $1 Year ended December 31, 2020 1 18 — 18 1 Year ended December 31, 2019 3 16 — 18 1 WPL Year ended December 31, 2021 $17 $6 $— $13 $10 Year ended December 31, 2020 6 7 9 5 17 Year ended December 31, 2019 7 1 2 4 6 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, 2021 $18 $12 $— $19 $11 Year ended December 31, 2020 7 25 9 23 18 Year ended December 31, 2019 10 17 2 22 7 IPL (c) Year ended December 31, 2021 $1 $6 $— $6 $1 Year ended December 31, 2020 1 18 — 18 1 Year ended December 31, 2019 3 16 — 18 1 WPL Year ended December 31, 2021 $17 $6 $— $13 $10 Year ended December 31, 2020 6 7 9 5 17 Year ended December 31, 2019 7 1 2 4 6 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, 2021 $18 $12 $— $19 $11 Year ended December 31, 2020 7 25 9 23 18 Year ended December 31, 2019 10 17 2 22 7 IPL (c) Year ended December 31, 2021 $1 $6 $— $6 $1 Year ended December 31, 2020 1 18 — 18 1 Year ended December 31, 2019 3 16 — 18 1 WPL Year ended December 31, 2021 $17 $6 $— $13 $10 Year ended December 31, 2020 6 7 9 5 17 Year ended December 31, 2019 7 1 2 4 6 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, 2021
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. Investment tax credits are deferred and amortized to income over the average lives of the related property. 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. Other tax credits reduce income tax expense in the year claimed. 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 2021, 2020 and 2019.
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, 2021, Alliant Energy’s and IPL’s cash and cash equivalents included $32 million of money market fund investments, with an interest rate of 0.04%. At December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6%
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: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9% 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. 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 West Riverside and 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, 2021, 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. Purchased 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 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. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliations of any under-/over-collection of energy efficiency costs from prior periods are also addressed in WPL’s periodic rate proceedings. 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 - Effective with the implementation of final rates covering the 2020 forward-looking Test Period, IPL recovers a return of, as well as earn a return on, its new 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 the new 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.
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 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. Investment tax credits are deferred and amortized to income over the average lives of the related property. 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. Other tax credits reduce income tax expense in the year claimed. 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 2021, 2020 and 2019.
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, 2021, Alliant Energy’s and IPL’s cash and cash equivalents included $32 million of money market fund investments, with an interest rate of 0.04%. At December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6%
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: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9% 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. 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 West Riverside and 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, 2021, 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. Purchased 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 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. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliations of any under-/over-collection of energy efficiency costs from prior periods are also addressed in WPL’s periodic rate proceedings. 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 - Effective with the implementation of final rates covering the 2020 forward-looking Test Period, IPL recovers a return of, as well as earn a return on, its new 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 the new 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.
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 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. Investment tax credits are deferred and amortized to income over the average lives of the related property. 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. Other tax credits reduce income tax expense in the year claimed. 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 2021, 2020 and 2019.
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, 2021, Alliant Energy’s and IPL’s cash and cash equivalents included $32 million of money market fund investments, with an interest rate of 0.04%. At December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6%
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: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9% 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. 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 West Riverside and 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, 2021, 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. Purchased 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 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. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliations of any under-/over-collection of energy efficiency costs from prior periods are also addressed in WPL’s periodic rate proceedings. 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 - Effective with the implementation of final rates covering the 2020 forward-looking Test Period, IPL recovers a return of, as well as earn a return on, its new 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 the new 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.
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 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, 2021
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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6%
Schedule of Allowance for Funds Used During Construction Rates	The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9%
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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6%
Schedule of Allowance for Funds Used During Construction Rates	The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9%
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 2021 2020 2019 2021 2020 2019 Electric - generation 3.4% 3.5% 3.8% 3.5% 3.5% 3.6% Electric - distribution 2.9% 2.8% 2.9% 2.6% 2.6% 2.6% Electric - other 5.7% 5.2% 5.3% 7.4% 6.1% 5.8% Gas 3.3% 3.3% 3.3% 2.4% 2.4% 2.5% Other 6.1% 6.3% 5.9% 5.4% 5.9% 5.6%
Schedule of Allowance for Funds Used During Construction Rates	The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows: 2021 2020 2019 IPL (Wind generation CWIP) 7.0% 7.1% 7.4% IPL (other CWIP) 7.2% 7.2% 7.5% WPL (retail jurisdiction) 7.0% 7.0% 6.8% WPL (wholesale jurisdiction) 5.6% 6.3% 6.9%

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2021 2020 2021 2020 Tax-related $934 $890 $884 $843 $50 $47 Pension and OPEB costs 462 580 228 291 234 289 AROs 128 119 89 81 39 38 Assets retired early 92 113 66 77 26 36 IPL’s DAEC PPA amendment 90 110 90 110 — — WPL’s Western Wisconsin gas distribution expansion investments 52 55 — — 52 55 Commodity cost recovery 42 4 2 1 40 3 Derivatives 8 26 4 13 4 13 Other 132 113 80 67 52 46 $1,940 $2,010 $1,443 $1,483 $497 $527
Schedule of 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, 2021 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $19 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 18 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 29 Return of remaining net book value through 2028 IUB and FERC WPL Nelson Dewey Units 1 and 2 and Edgewater Unit 3 2015 6 Return of and return on remaining net book value through 2022 PSCW and FERC WPL Edgewater Unit 4 2018 20 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 2021 2020 2021 2020 2021 2020 Tax-related $585 $732 $312 $331 $273 $401 Cost of removal obligations 384 367 252 238 132 129 Derivatives 166 28 77 25 89 3 Electric transmission cost recovery 51 68 27 39 24 29 WPL’s West Riverside liquidated damages 36 38 — — 36 38 Other 49 73 23 43 26 30 $1,271 $1,306 $691 $676 $580 $630
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 2021 2020 2021 2020 2021 2020 Tax-related $934 $890 $884 $843 $50 $47 Pension and OPEB costs 462 580 228 291 234 289 AROs 128 119 89 81 39 38 Assets retired early 92 113 66 77 26 36 IPL’s DAEC PPA amendment 90 110 90 110 — — WPL’s Western Wisconsin gas distribution expansion investments 52 55 — — 52 55 Commodity cost recovery 42 4 2 1 40 3 Derivatives 8 26 4 13 4 13 Other 132 113 80 67 52 46 $1,940 $2,010 $1,443 $1,483 $497 $527
Schedule of 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, 2021 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $19 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 18 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 29 Return of remaining net book value through 2028 IUB and FERC WPL Nelson Dewey Units 1 and 2 and Edgewater Unit 3 2015 6 Return of and return on remaining net book value through 2022 PSCW and FERC WPL Edgewater Unit 4 2018 20 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 2021 2020 2021 2020 2021 2020 Tax-related $585 $732 $312 $331 $273 $401 Cost of removal obligations 384 367 252 238 132 129 Derivatives 166 28 77 25 89 3 Electric transmission cost recovery 51 68 27 39 24 29 WPL’s West Riverside liquidated damages 36 38 — — 36 38 Other 49 73 23 43 26 30 $1,271 $1,306 $691 $676 $580 $630
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 2021 2020 2021 2020 2021 2020 Tax-related $934 $890 $884 $843 $50 $47 Pension and OPEB costs 462 580 228 291 234 289 AROs 128 119 89 81 39 38 Assets retired early 92 113 66 77 26 36 IPL’s DAEC PPA amendment 90 110 90 110 — — WPL’s Western Wisconsin gas distribution expansion investments 52 55 — — 52 55 Commodity cost recovery 42 4 2 1 40 3 Derivatives 8 26 4 13 4 13 Other 132 113 80 67 52 46 $1,940 $2,010 $1,443 $1,483 $497 $527
Schedule of 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, 2021 Recovery Regulatory Approval IPL Sutherland Units 1 and 3 2017 $19 Return of and return on remaining net book value through 2027 IUB and FERC IPL M.L. Kapp Unit 2 2018 18 Return of and return on remaining net book value through 2029 IUB and FERC IPL Analog electric meters 2019 29 Return of remaining net book value through 2028 IUB and FERC WPL Nelson Dewey Units 1 and 2 and Edgewater Unit 3 2015 6 Return of and return on remaining net book value through 2022 PSCW and FERC WPL Edgewater Unit 4 2018 20 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 2021 2020 2021 2020 2021 2020 Tax-related $585 $732 $312 $331 $273 $401 Cost of removal obligations 384 367 252 238 132 129 Derivatives 166 28 77 25 89 3 Electric transmission cost recovery 51 68 27 39 24 29 WPL’s West Riverside liquidated damages 36 38 — — 36 38 Other 49 73 23 43 26 30 $1,271 $1,306 $691 $676 $580 $630

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2021 2020 2021 2020 Utility: Electric plant: Generation in service $7,539 $8,222 $4,922 $4,884 $2,617 $3,338 Distribution in service 6,537 6,216 3,652 3,470 2,885 2,746 Other in service 540 536 363 358 177 178 Anticipated to be retired early (a) 2,094 1,269 487 459 1,607 810 Total electric plant 16,710 16,243 9,424 9,171 7,286 7,072 Gas plant in service 1,636 1,563 878 844 758 719 Other plant in service 621 534 398 354 223 180 Accumulated depreciation (5,263) (4,868) (2,897) (2,671) (2,366) (2,197) Net plant 13,704 13,472 7,803 7,698 5,901 5,774 Leased Sheboygan Falls Energy Facility, net (b) — — — — 21 27 Leased land for solar generation, net 11 — — — 11 — Construction work in progress 778 405 174 185 604 220 Other, net 7 7 6 6 1 1 Total utility 14,500 13,884 7,983 7,889 6,538 6,022 Non-utility and other: Non-utility Generation, net (c) 75 79 — — — — Corporate Services and other, net (d) 412 373 — — — — Total non-utility and other 487 452 — — — — Total property, plant and equipment $14,987 $14,336 $7,983 $7,889 $6,538 $6,022 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing by the end of 2022 and Edgewater Unit 5 by early 2023. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Unit 1 by the end of 2023 and Columbia Unit 2 by the end of 2024. 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, 2021. 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, 2021. As of December 31, 2021, net book values were $245 million for Lansing, $527 million for Edgewater Unit 5, and $460 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $100 million and $95 million for WPL as of December 31, 2021 and 2020, 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 $67 million and $63 million for Alliant Energy as of December 31, 2021 and 2020, respectively. (d) Less accumulated depreciation of $245 million and $210 million for Alliant Energy as of December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Equity $18 $39 $66 $7 $17 $35 $11 $22 $31 Debt 7 16 27 2 7 15 5 9 12 $25 $55 $93 $9 $24 $50 $16 $31 $43
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 2021 2020 2021 2020 2021 2020 Utility: Electric plant: Generation in service $7,539 $8,222 $4,922 $4,884 $2,617 $3,338 Distribution in service 6,537 6,216 3,652 3,470 2,885 2,746 Other in service 540 536 363 358 177 178 Anticipated to be retired early (a) 2,094 1,269 487 459 1,607 810 Total electric plant 16,710 16,243 9,424 9,171 7,286 7,072 Gas plant in service 1,636 1,563 878 844 758 719 Other plant in service 621 534 398 354 223 180 Accumulated depreciation (5,263) (4,868) (2,897) (2,671) (2,366) (2,197) Net plant 13,704 13,472 7,803 7,698 5,901 5,774 Leased Sheboygan Falls Energy Facility, net (b) — — — — 21 27 Leased land for solar generation, net 11 — — — 11 — Construction work in progress 778 405 174 185 604 220 Other, net 7 7 6 6 1 1 Total utility 14,500 13,884 7,983 7,889 6,538 6,022 Non-utility and other: Non-utility Generation, net (c) 75 79 — — — — Corporate Services and other, net (d) 412 373 — — — — Total non-utility and other 487 452 — — — — Total property, plant and equipment $14,987 $14,336 $7,983 $7,889 $6,538 $6,022 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing by the end of 2022 and Edgewater Unit 5 by early 2023. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Unit 1 by the end of 2023 and Columbia Unit 2 by the end of 2024. 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, 2021. 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, 2021. As of December 31, 2021, net book values were $245 million for Lansing, $527 million for Edgewater Unit 5, and $460 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $100 million and $95 million for WPL as of December 31, 2021 and 2020, 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 $67 million and $63 million for Alliant Energy as of December 31, 2021 and 2020, respectively. (d) Less accumulated depreciation of $245 million and $210 million for Alliant Energy as of December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Equity $18 $39 $66 $7 $17 $35 $11 $22 $31 Debt 7 16 27 2 7 15 5 9 12 $25 $55 $93 $9 $24 $50 $16 $31 $43
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 2021 2020 2021 2020 2021 2020 Utility: Electric plant: Generation in service $7,539 $8,222 $4,922 $4,884 $2,617 $3,338 Distribution in service 6,537 6,216 3,652 3,470 2,885 2,746 Other in service 540 536 363 358 177 178 Anticipated to be retired early (a) 2,094 1,269 487 459 1,607 810 Total electric plant 16,710 16,243 9,424 9,171 7,286 7,072 Gas plant in service 1,636 1,563 878 844 758 719 Other plant in service 621 534 398 354 223 180 Accumulated depreciation (5,263) (4,868) (2,897) (2,671) (2,366) (2,197) Net plant 13,704 13,472 7,803 7,698 5,901 5,774 Leased Sheboygan Falls Energy Facility, net (b) — — — — 21 27 Leased land for solar generation, net 11 — — — 11 — Construction work in progress 778 405 174 185 604 220 Other, net 7 7 6 6 1 1 Total utility 14,500 13,884 7,983 7,889 6,538 6,022 Non-utility and other: Non-utility Generation, net (c) 75 79 — — — — Corporate Services and other, net (d) 412 373 — — — — Total non-utility and other 487 452 — — — — Total property, plant and equipment $14,987 $14,336 $7,983 $7,889 $6,538 $6,022 (a) In 2020, IPL and WPL received approval from MISO to retire Lansing and Edgewater Unit 5, respectively, and currently anticipate retiring Lansing by the end of 2022 and Edgewater Unit 5 by early 2023. In 2021, WPL received approval from MISO to retire Columbia Units 1 and 2, and currently anticipates retiring Columbia Unit 1 by the end of 2023 and Columbia Unit 2 by the end of 2024. 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, 2021. 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, 2021. As of December 31, 2021, net book values were $245 million for Lansing, $527 million for Edgewater Unit 5, and $460 million for Columbia Units 1 and 2 in aggregate. (b) Less accumulated amortization of $100 million and $95 million for WPL as of December 31, 2021 and 2020, 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 $67 million and $63 million for Alliant Energy as of December 31, 2021 and 2020, respectively. (d) Less accumulated depreciation of $245 million and $210 million for Alliant Energy as of December 31, 2021 and 2020, 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Equity $18 $39 $66 $7 $17 $35 $11 $22 $31 Debt 7 16 27 2 7 15 5 9 12 $25 $55 $93 $9 $24 $50 $16 $31 $43

Jointly-Owned Electric Utilit_2

Jointly-Owned Electric Utility Plant (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $599 $214 $11 George Neal Unit 4 25.7% 193 100 2 George Neal Unit 3 28.0% 173 74 3 Louisa Unit 1 4.0% 40 23 — 1,005 411 16 WPL Columbia Units 1-2 53.5% 802 314 6 West Riverside Energy Center and Solar Garden 91.0% 706 33 3 Forward Wind Energy Center 42.6% 118 48 — 1,626 395 9 Alliant Energy $2,631 $806 $25
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, 2021 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $599 $214 $11 George Neal Unit 4 25.7% 193 100 2 George Neal Unit 3 28.0% 173 74 3 Louisa Unit 1 4.0% 40 23 — 1,005 411 16 WPL Columbia Units 1-2 53.5% 802 314 6 West Riverside Energy Center and Solar Garden 91.0% 706 33 3 Forward Wind Energy Center 42.6% 118 48 — 1,626 395 9 Alliant Energy $2,631 $806 $25
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, 2021 was as follows (dollars in millions): Ownership Electric Accumulated Provision Construction Interest % Plant for Depreciation Work in Progress IPL Ottumwa Unit 1 48.0% $599 $214 $11 George Neal Unit 4 25.7% 193 100 2 George Neal Unit 3 28.0% 173 74 3 Louisa Unit 1 4.0% 40 23 — 1,005 411 16 WPL Columbia Units 1-2 53.5% 802 314 6 West Riverside Energy Center and Solar Garden 91.0% 706 33 3 Forward Wind Energy Center 42.6% 118 48 — 1,626 395 9 Alliant Energy $2,631 $806 $25

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2021 2020 2021 2020 Customer $93 $101 $— $— $82 $92 Unbilled utility revenues 91 82 — — 91 82 Deferred proceeds 214 188 214 188 — — Other 53 59 28 23 25 35 Allowance for expected credit losses (11) (18) (1) (1) (10) (17) $440 $412 $241 $210 $188 $192
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 2021 2020 2019 2021 2020 2019 Outstanding aggregate cash proceeds $110 $96 $108 $46 $9 $36
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): 2021 2020 Customer accounts receivable $125 $114 Unbilled utility revenues 104 92 Receivables sold to third party 229 206 Less: cash proceeds 1 1 Deferred proceeds 228 205 Less: allowance for expected credit losses 14 17 Fair value of deferred proceeds $214 $188 Outstanding receivables past due $22 $27
Additional Attributes Of Receivables Sold Under The Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2021 2020 2019 Collections $2,134 $2,025 $2,193 Write-offs, net of recoveries 9 7 19
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 2021 2020 2021 2020 2021 2020 Customer $93 $101 $— $— $82 $92 Unbilled utility revenues 91 82 — — 91 82 Deferred proceeds 214 188 214 188 — — Other 53 59 28 23 25 35 Allowance for expected credit losses (11) (18) (1) (1) (10) (17) $440 $412 $241 $210 $188 $192
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 2021 2020 2019 2021 2020 2019 Outstanding aggregate cash proceeds $110 $96 $108 $46 $9 $36
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): 2021 2020 Customer accounts receivable $125 $114 Unbilled utility revenues 104 92 Receivables sold to third party 229 206 Less: cash proceeds 1 1 Deferred proceeds 228 205 Less: allowance for expected credit losses 14 17 Fair value of deferred proceeds $214 $188 Outstanding receivables past due $22 $27
Additional Attributes Of Receivables Sold Under The Agreement	Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): 2021 2020 2019 Collections $2,134 $2,025 $2,193 Write-offs, net of recoveries 9 7 19
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 2021 2020 2021 2020 2021 2020 Customer $93 $101 $— $— $82 $92 Unbilled utility revenues 91 82 — — 91 82 Deferred proceeds 214 188 214 188 — — Other 53 59 28 23 25 35 Allowance for expected credit losses (11) (18) (1) (1) (10) (17) $440 $412 $241 $210 $188 $192

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 2021 2020 2021 2020 2019 ATC Holdings 16%, 20% $338 $331 ($43) ($47) ($45) Non-utility wind farm in Oklahoma 50% 99 103 (4) (8) (5) Corporate venture investments Various 52 31 (13) (4) (1) Other Various 19 11 (2) (2) (2) $508 $476 ($62) ($61) ($53)
Summary Financial Information	Summary aggregate financial information from the financial statements of these holdings is as follows (in millions): Alliant Energy 2021 2020 2019 Revenues $802 $801 $783 Operating income 357 376 359 Net income 358 343 340 As of December 31: Current assets 112 121 Non-current assets 7,036 6,388 Current liabilities 455 317 Non-current liabilities 3,110 2,997 Noncontrolling interest 247 192

Common Equity (Tables)

Common Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Schedule of Common Equity [Line Items]
Common Stock Activity	A summary of Alliant Energy’s common stock activity was as follows: 2021 2020 2019 Shares outstanding, January 1 249,868,415 245,022,800 236,063,279 Equity forward agreements — 4,275,127 8,358,973 Shareowner Direct Plan 492,565 472,283 501,808 Equity-based compensation plans 113,549 98,205 101,478 Other — — (2,738) Shares outstanding, December 31 250,474,529 249,868,415 245,022,800

Preferred Stock (Tables)

Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2021
Class of Stock [Line Items]
Schedule of Carrying Value of Cumulative Preferred Stock	Information related to IPL’s cumulative preferred stock at December 31, 2020 was as follows (dollars in millions): Series Liquidation Preference/Stated Value Shares Authorized Shares Outstanding Carrying Value 5.1% $25 8,000,000 8,000,000 $200
IPL [Member]
Class of Stock [Line Items]
Schedule of Carrying Value of Cumulative Preferred Stock	Information related to IPL’s cumulative preferred stock at December 31, 2020 was as follows (dollars in millions): Series Liquidation Preference/Stated Value Shares Authorized Shares Outstanding Carrying Value 5.1% $25 8,000,000 8,000,000 $200

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Instrument [Line Items]
Schedule of Other Short-term Borrowings	Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2021 2020 2021 2020 2021 2020 Amount outstanding $515 $389 $— $— $236 $257 Weighted average interest rates 0.2% 0.2% N/A N/A 0.2% 0.1% Available credit facility capacity $485 $611 $250 $250 $64 $43 Alliant Energy IPL WPL For the year ended 2021 2020 2021 2020 2021 2020 Maximum amount outstanding (based on daily outstanding balances) $648 $495 $19 $8 $320 $266 Average amount outstanding (based on daily outstanding balances) $459 $292 $— $— $172 $117 Weighted average interest rates 0.2% 0.7% 0.2% 0.5% 0.1% 0.7%
Schedule of Long-term Debt	Long-term debt, net as of December 31 was as follows (dollars in millions): 2021 2020 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 (b) 300 300 — — — — 3,675 3,675 — 3,375 3,375 — Debentures (a): 2.25%, due 2022 250 — 250 250 — 250 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 (c) 300 — 300 — — — 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 2,450 — 2,450 2,150 — 2,150 Other: AEF term loan credit agreement through March 2022, 1% at December 31, 2021 (with Alliant Energy as guarantor) 300 — — 300 — — Corporate Services 3.45% senior notes, due 2022 (a) 75 — — 75 — — AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 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 — — Sheboygan Power, LLC 5.06% senior secured notes, due 2022 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 24 — — 31 — — Other, 1% at December 31, 2021, due 2022 to 2025 1 — — 2 — — 1,300 — — 1,308 — — Subtotal 7,425 3,675 2,450 6,833 3,375 2,150 Current maturities (633) — (250) (8) — — Unamortized debt issuance costs (42) (23) (15) (41) (22) (14) Unamortized debt (discount) and premium, net (15) (9) (6) (15) (8) (6) Long-term debt, net (d) $6,735 $3,643 $2,179 $6,769 $3,345 $2,130 (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 November 2021, IPL issued $300 million of 3.1% senior debentures due 2051. The net proceeds from the issuance were used by IPL to retire its cumulative preferred stock in 2021 and for general corporate purposes. (c) In September 2021, WPL issued $300 million of 1.95% debentures due 2031. The debentures were issued as green bonds, and an amount in excess of the net proceeds was disbursed for the construction and development of WPL’s wind and solar EGUs. (d) There were no significant sinking fund requirements related to the outstanding long-term debt.
Schedule of Maturities of Long-term Debt	At December 31, 2021, long-term debt maturities for 2022 through 2026 were as follows (in millions): 2022 2023 2024 2025 2026 IPL $— $— $500 $300 $— WPL 250 — — — — Corporate Services 75 — — — — AEF 308 408 9 — 200 Alliant Energy $633 $408 $509 $300 $200
IPL [Member]
Debt Instrument [Line Items]
Schedule of Other Short-term Borrowings	Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2021 2020 2021 2020 2021 2020 Amount outstanding $515 $389 $— $— $236 $257 Weighted average interest rates 0.2% 0.2% N/A N/A 0.2% 0.1% Available credit facility capacity $485 $611 $250 $250 $64 $43 Alliant Energy IPL WPL For the year ended 2021 2020 2021 2020 2021 2020 Maximum amount outstanding (based on daily outstanding balances) $648 $495 $19 $8 $320 $266 Average amount outstanding (based on daily outstanding balances) $459 $292 $— $— $172 $117 Weighted average interest rates 0.2% 0.7% 0.2% 0.5% 0.1% 0.7%
Schedule of Long-term Debt	Long-term debt, net as of December 31 was as follows (dollars in millions): 2021 2020 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 (b) 300 300 — — — — 3,675 3,675 — 3,375 3,375 — Debentures (a): 2.25%, due 2022 250 — 250 250 — 250 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 (c) 300 — 300 — — — 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 2,450 — 2,450 2,150 — 2,150 Other: AEF term loan credit agreement through March 2022, 1% at December 31, 2021 (with Alliant Energy as guarantor) 300 — — 300 — — Corporate Services 3.45% senior notes, due 2022 (a) 75 — — 75 — — AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 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 — — Sheboygan Power, LLC 5.06% senior secured notes, due 2022 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 24 — — 31 — — Other, 1% at December 31, 2021, due 2022 to 2025 1 — — 2 — — 1,300 — — 1,308 — — Subtotal 7,425 3,675 2,450 6,833 3,375 2,150 Current maturities (633) — (250) (8) — — Unamortized debt issuance costs (42) (23) (15) (41) (22) (14) Unamortized debt (discount) and premium, net (15) (9) (6) (15) (8) (6) Long-term debt, net (d) $6,735 $3,643 $2,179 $6,769 $3,345 $2,130 (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 November 2021, IPL issued $300 million of 3.1% senior debentures due 2051. The net proceeds from the issuance were used by IPL to retire its cumulative preferred stock in 2021 and for general corporate purposes. (c) In September 2021, WPL issued $300 million of 1.95% debentures due 2031. The debentures were issued as green bonds, and an amount in excess of the net proceeds was disbursed for the construction and development of WPL’s wind and solar EGUs. (d) There were no significant sinking fund requirements related to the outstanding long-term debt.
Schedule of Maturities of Long-term Debt	At December 31, 2021, long-term debt maturities for 2022 through 2026 were as follows (in millions): 2022 2023 2024 2025 2026 IPL $— $— $500 $300 $— WPL 250 — — — — Corporate Services 75 — — — — AEF 308 408 9 — 200 Alliant Energy $633 $408 $509 $300 $200
WPL [Member]
Debt Instrument [Line Items]
Schedule of Other Short-term Borrowings	Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions): Alliant Energy IPL WPL December 31 2021 2020 2021 2020 2021 2020 Amount outstanding $515 $389 $— $— $236 $257 Weighted average interest rates 0.2% 0.2% N/A N/A 0.2% 0.1% Available credit facility capacity $485 $611 $250 $250 $64 $43 Alliant Energy IPL WPL For the year ended 2021 2020 2021 2020 2021 2020 Maximum amount outstanding (based on daily outstanding balances) $648 $495 $19 $8 $320 $266 Average amount outstanding (based on daily outstanding balances) $459 $292 $— $— $172 $117 Weighted average interest rates 0.2% 0.7% 0.2% 0.5% 0.1% 0.7%
Schedule of Long-term Debt	Long-term debt, net as of December 31 was as follows (dollars in millions): 2021 2020 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 (b) 300 300 — — — — 3,675 3,675 — 3,375 3,375 — Debentures (a): 2.25%, due 2022 250 — 250 250 — 250 3.05%, due 2027 300 — 300 300 — 300 3%, due 2029 350 — 350 350 — 350 1.95%, due 2031 (c) 300 — 300 — — — 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 2,450 — 2,450 2,150 — 2,150 Other: AEF term loan credit agreement through March 2022, 1% at December 31, 2021 (with Alliant Energy as guarantor) 300 — — 300 — — Corporate Services 3.45% senior notes, due 2022 (a) 75 — — 75 — — AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a) 400 — — 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 — — Sheboygan Power, LLC 5.06% senior secured notes, due 2022 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a) 24 — — 31 — — Other, 1% at December 31, 2021, due 2022 to 2025 1 — — 2 — — 1,300 — — 1,308 — — Subtotal 7,425 3,675 2,450 6,833 3,375 2,150 Current maturities (633) — (250) (8) — — Unamortized debt issuance costs (42) (23) (15) (41) (22) (14) Unamortized debt (discount) and premium, net (15) (9) (6) (15) (8) (6) Long-term debt, net (d) $6,735 $3,643 $2,179 $6,769 $3,345 $2,130 (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 November 2021, IPL issued $300 million of 3.1% senior debentures due 2051. The net proceeds from the issuance were used by IPL to retire its cumulative preferred stock in 2021 and for general corporate purposes. (c) In September 2021, WPL issued $300 million of 1.95% debentures due 2031. The debentures were issued as green bonds, and an amount in excess of the net proceeds was disbursed for the construction and development of WPL’s wind and solar EGUs. (d) There were no significant sinking fund requirements related to the outstanding long-term debt.
Schedule of Maturities of Long-term Debt	At December 31, 2021, long-term debt maturities for 2022 through 2026 were as follows (in millions): 2022 2023 2024 2025 2026 IPL $— $— $500 $300 $— WPL 250 — — — — Corporate Services 75 — — — — AEF 308 408 9 — 200 Alliant Energy $633 $408 $509 $300 $200

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Line Items]
Schedule of Operating Lease Details	Operating lease details are as follows (dollars in millions): December 31, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 years Weighted average discount rate 4% 4% 4% 4% 4% 4%
Schedule of Finance Lease Details	Finance lease details are as follows (dollars in millions): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13
Schedule of Operating Lease Liability Maturities	As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
Schedule of Finance Lease Liability Maturities	As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
IPL [Member]
Leases [Line Items]
Schedule of Operating Lease Details	Operating lease details are as follows (dollars in millions): December 31, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 years Weighted average discount rate 4% 4% 4% 4% 4% 4%
Schedule of Operating Lease Liability Maturities	As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
WPL [Member]
Leases [Line Items]
Schedule of Operating Lease Details	Operating lease details are as follows (dollars in millions): December 31, 2021 December 31, 2020 Alliant Energy IPL WPL Alliant Energy IPL WPL Property, plant and equipment, net $14 $9 $5 $15 $9 $6 Other current liabilities $2 $1 $1 $2 $1 $1 Other liabilities 12 8 4 13 8 5 Total operating lease liabilities $14 $9 $5 $15 $9 $6 Weighted average remaining lease term 9 years 11 years 8 years 10 years 11 years 9 years Weighted average discount rate 4% 4% 4% 4% 4% 4%
Schedule of Finance Lease Details	Finance lease details are as follows (dollars in millions): Alliant Energy WPL December 31, 2021 December 31, 2021 December 31, 2020 Property, plant and equipment, net: Sheboygan Falls Energy Facility n/a $21 $27 Leased land for solar generation $11 11 — $11 $32 $27 Other current liabilities: Sheboygan Falls Energy Facility n/a $10 $9 Leased land for solar generation $1 1 — 1 11 9 Other liabilities: Sheboygan Falls Energy Facility n/a 31 42 Leased land for solar generation 11 11 — 11 42 42 Total finance lease liabilities $12 $53 $51 Weighted average remaining lease term 34 years 10 years 4 years Weighted average discount rate 3% 9% 11% 2021 2021 2020 2019 Depreciation and amortization expenses $— $6 $6 $6 Interest expense — 5 6 7 Total finance lease expense $— $11 $12 $13
Schedule of Operating Lease Liability Maturities	As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53
Schedule of Finance Lease Liability Maturities	As of December 31, 2021, expected maturities of lease liabilities were as follows (in millions): 2022 2023 2024 2025 2026 Thereafter Total Less: amount representing interest Present value of minimum lease payments Operating Leases: Alliant Energy $2 $2 $2 $2 $2 $7 $17 $3 $14 IPL 1 1 1 1 1 6 11 2 9 WPL 1 1 1 1 1 1 6 1 5 Finance Leases: Alliant Energy — — — — 1 19 20 8 12 WPL 15 15 15 6 1 19 71 18 53

Revenues (Tables)

Revenues (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Electric Utility: Retail - residential $1,115 $1,093 $1,092 $620 $602 $601 $495 $491 $491 Retail - commercial 763 718 770 508 474 510 255 244 260 Retail - industrial 893 841 889 505 488 504 388 353 385 Wholesale 187 168 177 57 57 64 130 111 113 Bulk power and other 123 100 136 62 74 102 61 26 34 Total Electric Utility 3,081 2,920 3,064 1,752 1,695 1,781 1,329 1,225 1,283 Gas Utility: Retail - residential 257 214 259 146 116 149 111 98 110 Retail - commercial 139 107 133 79 59 75 60 48 58 Retail - industrial 17 12 16 12 8 12 5 4 4 Transportation/other 43 40 47 28 25 28 15 15 19 Total Gas Utility 456 373 455 265 208 264 191 165 191 Other Utility: Steam 36 36 37 36 36 37 — — — Other utility 13 13 9 10 8 7 3 5 2 Total Other Utility 49 49 46 46 44 44 3 5 2 Non-Utility and Other: Travero and other 83 74 83 — — — — — — Total Non-Utility and Other 83 74 83 — — — — — — Total revenues $3,669 $3,416 $3,648 $2,063 $1,947 $2,089 $1,523 $1,395 $1,476
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Electric Utility: Retail - residential $1,115 $1,093 $1,092 $620 $602 $601 $495 $491 $491 Retail - commercial 763 718 770 508 474 510 255 244 260 Retail - industrial 893 841 889 505 488 504 388 353 385 Wholesale 187 168 177 57 57 64 130 111 113 Bulk power and other 123 100 136 62 74 102 61 26 34 Total Electric Utility 3,081 2,920 3,064 1,752 1,695 1,781 1,329 1,225 1,283 Gas Utility: Retail - residential 257 214 259 146 116 149 111 98 110 Retail - commercial 139 107 133 79 59 75 60 48 58 Retail - industrial 17 12 16 12 8 12 5 4 4 Transportation/other 43 40 47 28 25 28 15 15 19 Total Gas Utility 456 373 455 265 208 264 191 165 191 Other Utility: Steam 36 36 37 36 36 37 — — — Other utility 13 13 9 10 8 7 3 5 2 Total Other Utility 49 49 46 46 44 44 3 5 2 Non-Utility and Other: Travero and other 83 74 83 — — — — — — Total Non-Utility and Other 83 74 83 — — — — — — Total revenues $3,669 $3,416 $3,648 $2,063 $1,947 $2,089 $1,523 $1,395 $1,476
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Electric Utility: Retail - residential $1,115 $1,093 $1,092 $620 $602 $601 $495 $491 $491 Retail - commercial 763 718 770 508 474 510 255 244 260 Retail - industrial 893 841 889 505 488 504 388 353 385 Wholesale 187 168 177 57 57 64 130 111 113 Bulk power and other 123 100 136 62 74 102 61 26 34 Total Electric Utility 3,081 2,920 3,064 1,752 1,695 1,781 1,329 1,225 1,283 Gas Utility: Retail - residential 257 214 259 146 116 149 111 98 110 Retail - commercial 139 107 133 79 59 75 60 48 58 Retail - industrial 17 12 16 12 8 12 5 4 4 Transportation/other 43 40 47 28 25 28 15 15 19 Total Gas Utility 456 373 455 265 208 264 191 165 191 Other Utility: Steam 36 36 37 36 36 37 — — — Other utility 13 13 9 10 8 7 3 5 2 Total Other Utility 49 49 46 46 44 44 3 5 2 Non-Utility and Other: Travero and other 83 74 83 — — — — — — Total Non-Utility and Other 83 74 83 — — — — — — Total revenues $3,669 $3,416 $3,648 $2,063 $1,947 $2,089 $1,523 $1,395 $1,476

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Current tax expense (benefit): Federal $1 $1 ($7) ($21) $6 ($11) $22 ($11) $12 State 3 8 24 (1) (1) 24 6 7 13 IPL’s tax benefit riders — — (4) — — (4) — — — Deferred tax expense (benefit): Federal 9 22 70 73 30 26 (75) (9) 31 State 15 8 42 — (2) 31 11 10 6 Production tax credits (101) (95) (55) (87) (80) (42) (14) (15) (13) Investment tax credits (1) (1) (1) — — — (1) (1) — ($74) ($57) $69 ($36) ($47) $24 ($51) ($19) $49
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 from continuing operations before income taxes. Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Statutory federal income tax rate 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % State income taxes, net of federal benefits 2 2 7 (1) (1) 8 6 6 6 Amortization of excess deferred taxes (Refer to Note 2 ) (18) (13) (1) (4) (5) — (43) (26) (2) Production tax credits (17) (17) (9) (27) (28) (13) (6) (7) (5) Effect of rate-making on property-related differences (1) (3) (6) (2) (4) (10) (1) (2) (3) Adjustment for prior period taxes 1 1 1 2 1 3 — — — IPL’s tax benefit riders — — (1) — — (1) — — — Other items, net — (1) (1) — — — (1) — — Overall income tax rate (12 %) (10 %) 11 % (11 %) (16 %) 8 % (24 %) (8 %) 17 %
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 2021 2020 2021 2020 2021 2020 Deferred tax liabilities: Property $2,389 $2,232 $1,416 $1,312 $913 $854 ATC Holdings 123 116 — — — — Other 111 101 76 83 50 41 Total deferred tax liabilities 2,623 2,449 1,492 1,395 963 895 Deferred tax assets: Federal credit carryforwards 560 454 345 258 192 175 Net operating losses carryforwards - federal 39 77 36 71 — 1 Net operating losses carryforwards - state 38 37 3 1 — — Other 65 73 25 30 18 18 Subtotal deferred tax assets 702 641 409 360 210 194 Valuation allowances (6) (6) — — — (1) Total deferred tax assets 696 635 409 360 210 193 Total deferred tax liabilities, net $1,927 $1,814 $1,083 $1,035 $753 $702
Summary Of Tax Credit Carryforwards	At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $186 $172 $1 State net operating losses 2022-2041 619 28 2 Federal tax credits 2022-2041 560 345 192
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) 2018 - 2020 Consolidated Iowa income tax returns (b) 2018 - 2020 Wisconsin combined tax returns (c) 2017 - 2020 (a) The 2018 and 2019 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Current tax expense (benefit): Federal $1 $1 ($7) ($21) $6 ($11) $22 ($11) $12 State 3 8 24 (1) (1) 24 6 7 13 IPL’s tax benefit riders — — (4) — — (4) — — — Deferred tax expense (benefit): Federal 9 22 70 73 30 26 (75) (9) 31 State 15 8 42 — (2) 31 11 10 6 Production tax credits (101) (95) (55) (87) (80) (42) (14) (15) (13) Investment tax credits (1) (1) (1) — — — (1) (1) — ($74) ($57) $69 ($36) ($47) $24 ($51) ($19) $49
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 from continuing operations before income taxes. Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Statutory federal income tax rate 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % State income taxes, net of federal benefits 2 2 7 (1) (1) 8 6 6 6 Amortization of excess deferred taxes (Refer to Note 2 ) (18) (13) (1) (4) (5) — (43) (26) (2) Production tax credits (17) (17) (9) (27) (28) (13) (6) (7) (5) Effect of rate-making on property-related differences (1) (3) (6) (2) (4) (10) (1) (2) (3) Adjustment for prior period taxes 1 1 1 2 1 3 — — — IPL’s tax benefit riders — — (1) — — (1) — — — Other items, net — (1) (1) — — — (1) — — Overall income tax rate (12 %) (10 %) 11 % (11 %) (16 %) 8 % (24 %) (8 %) 17 %
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 2021 2020 2021 2020 2021 2020 Deferred tax liabilities: Property $2,389 $2,232 $1,416 $1,312 $913 $854 ATC Holdings 123 116 — — — — Other 111 101 76 83 50 41 Total deferred tax liabilities 2,623 2,449 1,492 1,395 963 895 Deferred tax assets: Federal credit carryforwards 560 454 345 258 192 175 Net operating losses carryforwards - federal 39 77 36 71 — 1 Net operating losses carryforwards - state 38 37 3 1 — — Other 65 73 25 30 18 18 Subtotal deferred tax assets 702 641 409 360 210 194 Valuation allowances (6) (6) — — — (1) Total deferred tax assets 696 635 409 360 210 193 Total deferred tax liabilities, net $1,927 $1,814 $1,083 $1,035 $753 $702
Summary Of Tax Credit Carryforwards	At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $186 $172 $1 State net operating losses 2022-2041 619 28 2 Federal tax credits 2022-2041 560 345 192
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) 2018 - 2020 Consolidated Iowa income tax returns (b) 2018 - 2020 Wisconsin combined tax returns (c) 2017 - 2020 (a) The 2018 and 2019 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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Current tax expense (benefit): Federal $1 $1 ($7) ($21) $6 ($11) $22 ($11) $12 State 3 8 24 (1) (1) 24 6 7 13 IPL’s tax benefit riders — — (4) — — (4) — — — Deferred tax expense (benefit): Federal 9 22 70 73 30 26 (75) (9) 31 State 15 8 42 — (2) 31 11 10 6 Production tax credits (101) (95) (55) (87) (80) (42) (14) (15) (13) Investment tax credits (1) (1) (1) — — — (1) (1) — ($74) ($57) $69 ($36) ($47) $24 ($51) ($19) $49
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 from continuing operations before income taxes. Alliant Energy IPL WPL 2021 2020 2019 2021 2020 2019 2021 2020 2019 Statutory federal income tax rate 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % 21 % State income taxes, net of federal benefits 2 2 7 (1) (1) 8 6 6 6 Amortization of excess deferred taxes (Refer to Note 2 ) (18) (13) (1) (4) (5) — (43) (26) (2) Production tax credits (17) (17) (9) (27) (28) (13) (6) (7) (5) Effect of rate-making on property-related differences (1) (3) (6) (2) (4) (10) (1) (2) (3) Adjustment for prior period taxes 1 1 1 2 1 3 — — — IPL’s tax benefit riders — — (1) — — (1) — — — Other items, net — (1) (1) — — — (1) — — Overall income tax rate (12 %) (10 %) 11 % (11 %) (16 %) 8 % (24 %) (8 %) 17 %
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 2021 2020 2021 2020 2021 2020 Deferred tax liabilities: Property $2,389 $2,232 $1,416 $1,312 $913 $854 ATC Holdings 123 116 — — — — Other 111 101 76 83 50 41 Total deferred tax liabilities 2,623 2,449 1,492 1,395 963 895 Deferred tax assets: Federal credit carryforwards 560 454 345 258 192 175 Net operating losses carryforwards - federal 39 77 36 71 — 1 Net operating losses carryforwards - state 38 37 3 1 — — Other 65 73 25 30 18 18 Subtotal deferred tax assets 702 641 409 360 210 194 Valuation allowances (6) (6) — — — (1) Total deferred tax assets 696 635 409 360 210 193 Total deferred tax liabilities, net $1,927 $1,814 $1,083 $1,035 $753 $702
Summary Of Tax Credit Carryforwards	At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses 2037 $186 $172 $1 State net operating losses 2022-2041 619 28 2 Federal tax credits 2022-2041 560 345 192
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) 2018 - 2020 Consolidated Iowa income tax returns (b) 2018 - 2020 Wisconsin combined tax returns (c) 2017 - 2020 (a) The 2018 and 2019 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, 2021
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 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Discount rate for net periodic cost 2.57% 3.48% 4.34% 2.31% 3.40% 4.24% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.80% 4.50% 5.44% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 4.18% 4.76% 5.52% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.65% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Discount rate for net periodic cost 2.61% 3.51% 4.35% 2.28% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 5.10% 4.50% 5.60% Rate of compensation increase 3.30% 3.65% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Discount rate for net periodic cost 2.64% 3.50% 4.35% 2.27% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.02% 3.28% 3.81% Rate of compensation increase 3.30% 3.65% 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. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $11 $11 $10 $4 $3 $3 Interest cost 34 43 50 5 7 9 Expected return on plan assets (a) (69) (70) (60) (5) (5) (5) Amortization of prior service credit (b) — — (1) — — — Amortization of actuarial loss (c) 39 34 36 5 3 3 Settlement losses (d) — 12 — — — — $15 $30 $35 $9 $8 $10 IPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $7 $7 $6 $1 $1 $1 Interest cost 16 20 23 2 3 3 Expected return on plan assets (a) (32) (33) (28) (3) (4) (4) Amortization of actuarial loss (c) 17 15 15 2 1 2 Settlement losses (d) — 7 — — — — $8 $16 $16 $2 $1 $2 WPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $4 $4 $3 $1 $2 $1 Interest cost 15 19 21 2 3 3 Expected return on plan assets (a) (31) (31) (26) — (1) (1) Amortization of prior service credit (b) — — — — (1) — Amortization of actuarial loss (c) 19 16 18 2 2 2 $7 $8 $16 $5 $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 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 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $1,351 $1,280 $227 $214 Service cost 11 11 4 3 Interest cost 34 43 5 7 Plan participants’ contributions — — 5 4 Actuarial (gain) loss (46) 132 (12) 18 Gross benefits paid (99) (115) (19) (19) Net benefit obligation at December 31 1,251 1,351 210 227 Change in plan assets: Fair value of plan assets at January 1 984 931 108 105 Actual return on plan assets 87 108 4 11 Employer contributions 39 60 8 7 Plan participants’ contributions — — 5 4 Gross benefits paid (99) (115) (19) (19) Fair value of plan assets at December 31 1,011 984 106 108 Under funded status at December 31 ($240) ($367) ($104) ($119) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $13 $8 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (238) (365) (109) (119) Net amounts recognized at December 31 ($240) ($367) ($104) ($119) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $429 $533 $38 $54 Prior service credit (4) (5) (1) (1) $425 $528 $37 $53 Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $615 $581 $91 $86 Service cost 7 7 1 1 Interest cost 16 20 2 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss (23) 60 (4) 8 Gross benefits paid (48) (53) (8) (8) Net benefit obligation at December 31 567 615 84 91 Change in plan assets: Fair value of plan assets at January 1 453 436 74 72 Actual return on plan assets 40 51 4 7 Employer contributions 17 19 2 2 Plan participants’ contributions — — 2 1 Gross benefits paid (48) (53) (8) (8) Fair value of plan assets at December 31 462 453 74 74 Under funded status at December 31 ($105) ($162) ($10) ($17) Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $10 $4 Current liabilities — (1) (2) (2) Pension and other benefit obligations (105) (161) (18) (19) Net amounts recognized at December 31 ($105) ($162) ($10) ($17) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $180 $228 $13 $20 Prior service credit (1) (1) — — $179 $227 $13 $20 Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $588 $550 $89 $85 Service cost 4 4 1 2 Interest cost 15 19 2 3 Plan participants’ contributions — — 2 2 Actuarial (gain) loss (18) 55 (5) 5 Gross benefits paid (43) (40) (8) (8) Net benefit obligation at December 31 546 588 81 89 Change in plan assets: Fair value of plan assets at January 1 436 406 18 17 Actual return on plan assets 39 48 — 2 Employer contributions 18 22 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (43) (40) (8) (8) Fair value of plan assets at December 31 450 436 17 18 Under funded status at December 31 ($96) ($152) ($64) ($71) Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (6) (6) Pension and other benefit obligations (96) (152) (61) (68) Net amounts recognized at December 31 ($96) ($152) ($64) ($71) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $188 $233 $18 $25 Prior service credit (1) (1) (1) (1) $187 $232 $17 $24
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 2021 2020 2021 2020 Accumulated benefit obligations $1,214 $1,305 $210 $227 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 1,214 1,305 210 227 Fair value of plan assets 1,011 984 106 108 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 1,251 1,351 N/A N/A Fair value of plan assets 1,011 984 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Accumulated benefit obligations $546 $589 $84 $91 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 546 589 84 91 Fair value of plan assets 462 453 74 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 567 615 N/A N/A Fair value of plan assets 462 453 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Accumulated benefit obligations $532 $573 $81 $89 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 532 573 81 89 Fair value of plan assets 450 436 17 18 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 546 588 N/A N/A Fair value of plan assets 450 436 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 2021 2020 2021 2020 Regulatory assets $35 $44 $30 $34
Estimated Future Employer Contributions	Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2022 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $2 $— $— 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 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $85 $83 $82 $82 $83 $387 OPEB 18 17 17 17 16 71 $103 $100 $99 $99 $99 $458 IPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $41 $40 $39 $39 $38 $174 OPEB 7 7 7 7 7 28 $48 $47 $46 $46 $45 $202 WPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $37 $36 $35 $35 $34 $163 OPEB 7 7 7 7 6 27 $44 $43 $42 $42 $40 $190
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Compensation expense $14 $16 $26 $8 $9 $15 $6 $6 $10 Income tax benefits 4 4 7 2 2 4 2 2 3
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): 2021 2020 Carrying value $12 $11 Fair market value 24 20
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 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Discount rate for net periodic cost 2.57% 3.48% 4.34% 2.31% 3.40% 4.24% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.80% 4.50% 5.44% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 4.18% 4.76% 5.52% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.65% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Discount rate for net periodic cost 2.61% 3.51% 4.35% 2.28% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 5.10% 4.50% 5.60% Rate of compensation increase 3.30% 3.65% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Discount rate for net periodic cost 2.64% 3.50% 4.35% 2.27% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.02% 3.28% 3.81% Rate of compensation increase 3.30% 3.65% 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. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $11 $11 $10 $4 $3 $3 Interest cost 34 43 50 5 7 9 Expected return on plan assets (a) (69) (70) (60) (5) (5) (5) Amortization of prior service credit (b) — — (1) — — — Amortization of actuarial loss (c) 39 34 36 5 3 3 Settlement losses (d) — 12 — — — — $15 $30 $35 $9 $8 $10 IPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $7 $7 $6 $1 $1 $1 Interest cost 16 20 23 2 3 3 Expected return on plan assets (a) (32) (33) (28) (3) (4) (4) Amortization of actuarial loss (c) 17 15 15 2 1 2 Settlement losses (d) — 7 — — — — $8 $16 $16 $2 $1 $2 WPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $4 $4 $3 $1 $2 $1 Interest cost 15 19 21 2 3 3 Expected return on plan assets (a) (31) (31) (26) — (1) (1) Amortization of prior service credit (b) — — — — (1) — Amortization of actuarial loss (c) 19 16 18 2 2 2 $7 $8 $16 $5 $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 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 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $1,351 $1,280 $227 $214 Service cost 11 11 4 3 Interest cost 34 43 5 7 Plan participants’ contributions — — 5 4 Actuarial (gain) loss (46) 132 (12) 18 Gross benefits paid (99) (115) (19) (19) Net benefit obligation at December 31 1,251 1,351 210 227 Change in plan assets: Fair value of plan assets at January 1 984 931 108 105 Actual return on plan assets 87 108 4 11 Employer contributions 39 60 8 7 Plan participants’ contributions — — 5 4 Gross benefits paid (99) (115) (19) (19) Fair value of plan assets at December 31 1,011 984 106 108 Under funded status at December 31 ($240) ($367) ($104) ($119) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $13 $8 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (238) (365) (109) (119) Net amounts recognized at December 31 ($240) ($367) ($104) ($119) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $429 $533 $38 $54 Prior service credit (4) (5) (1) (1) $425 $528 $37 $53 Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $615 $581 $91 $86 Service cost 7 7 1 1 Interest cost 16 20 2 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss (23) 60 (4) 8 Gross benefits paid (48) (53) (8) (8) Net benefit obligation at December 31 567 615 84 91 Change in plan assets: Fair value of plan assets at January 1 453 436 74 72 Actual return on plan assets 40 51 4 7 Employer contributions 17 19 2 2 Plan participants’ contributions — — 2 1 Gross benefits paid (48) (53) (8) (8) Fair value of plan assets at December 31 462 453 74 74 Under funded status at December 31 ($105) ($162) ($10) ($17) Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $10 $4 Current liabilities — (1) (2) (2) Pension and other benefit obligations (105) (161) (18) (19) Net amounts recognized at December 31 ($105) ($162) ($10) ($17) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $180 $228 $13 $20 Prior service credit (1) (1) — — $179 $227 $13 $20 Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $588 $550 $89 $85 Service cost 4 4 1 2 Interest cost 15 19 2 3 Plan participants’ contributions — — 2 2 Actuarial (gain) loss (18) 55 (5) 5 Gross benefits paid (43) (40) (8) (8) Net benefit obligation at December 31 546 588 81 89 Change in plan assets: Fair value of plan assets at January 1 436 406 18 17 Actual return on plan assets 39 48 — 2 Employer contributions 18 22 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (43) (40) (8) (8) Fair value of plan assets at December 31 450 436 17 18 Under funded status at December 31 ($96) ($152) ($64) ($71) Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (6) (6) Pension and other benefit obligations (96) (152) (61) (68) Net amounts recognized at December 31 ($96) ($152) ($64) ($71) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $188 $233 $18 $25 Prior service credit (1) (1) (1) (1) $187 $232 $17 $24
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 2021 2020 2021 2020 Accumulated benefit obligations $1,214 $1,305 $210 $227 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 1,214 1,305 210 227 Fair value of plan assets 1,011 984 106 108 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 1,251 1,351 N/A N/A Fair value of plan assets 1,011 984 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Accumulated benefit obligations $546 $589 $84 $91 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 546 589 84 91 Fair value of plan assets 462 453 74 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 567 615 N/A N/A Fair value of plan assets 462 453 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Accumulated benefit obligations $532 $573 $81 $89 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 532 573 81 89 Fair value of plan assets 450 436 17 18 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 546 588 N/A N/A Fair value of plan assets 450 436 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 2021 2020 2021 2020 Regulatory assets $35 $44 $30 $34
Estimated Future Employer Contributions	Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2022 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $2 $— $— 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 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $85 $83 $82 $82 $83 $387 OPEB 18 17 17 17 16 71 $103 $100 $99 $99 $99 $458 IPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $41 $40 $39 $39 $38 $174 OPEB 7 7 7 7 7 28 $48 $47 $46 $46 $45 $202 WPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $37 $36 $35 $35 $34 $163 OPEB 7 7 7 7 6 27 $44 $43 $42 $42 $40 $190
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Compensation expense $14 $16 $26 $8 $9 $15 $6 $6 $10 Income tax benefits 4 4 7 2 2 4 2 2 3
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 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.91% 2.57% 3.48% 2.81% 2.31% 3.40% Discount rate for net periodic cost 2.57% 3.48% 4.34% 2.31% 3.40% 4.24% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.80% 4.50% 5.44% Interest crediting rate for Alliant Energy Cash Balance Pension Plan 4.18% 4.76% 5.52% N/A N/A N/A Rate of compensation increase 3.30% - 4.50% 3.65% - 4.50% 3.65% - 4.50% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans IPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.61% 3.51% 2.80% 2.28% 3.39% Discount rate for net periodic cost 2.61% 3.51% 4.35% 2.28% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 5.10% 4.50% 5.60% Rate of compensation increase 3.30% 3.65% 3.65% N/A N/A N/A Qualified Defined Benefit Pension Plan OPEB Plans WPL 2021 2020 2019 2021 2020 2019 Discount rate for benefit obligations 2.94% 2.64% 3.50% 2.79% 2.27% 3.39% Discount rate for net periodic cost 2.64% 3.50% 4.35% 2.27% 3.39% 4.23% Expected rate of return on plan assets 7.10% 7.10% 7.60% 4.02% 3.28% 3.81% Rate of compensation increase 3.30% 3.65% 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. Alliant Energy Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $11 $11 $10 $4 $3 $3 Interest cost 34 43 50 5 7 9 Expected return on plan assets (a) (69) (70) (60) (5) (5) (5) Amortization of prior service credit (b) — — (1) — — — Amortization of actuarial loss (c) 39 34 36 5 3 3 Settlement losses (d) — 12 — — — — $15 $30 $35 $9 $8 $10 IPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $7 $7 $6 $1 $1 $1 Interest cost 16 20 23 2 3 3 Expected return on plan assets (a) (32) (33) (28) (3) (4) (4) Amortization of actuarial loss (c) 17 15 15 2 1 2 Settlement losses (d) — 7 — — — — $8 $16 $16 $2 $1 $2 WPL Defined Benefit Pension Plans OPEB Plans 2021 2020 2019 2021 2020 2019 Service cost $4 $4 $3 $1 $2 $1 Interest cost 15 19 21 2 3 3 Expected return on plan assets (a) (31) (31) (26) — (1) (1) Amortization of prior service credit (b) — — — — (1) — Amortization of actuarial loss (c) 19 16 18 2 2 2 $7 $8 $16 $5 $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 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 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $1,351 $1,280 $227 $214 Service cost 11 11 4 3 Interest cost 34 43 5 7 Plan participants’ contributions — — 5 4 Actuarial (gain) loss (46) 132 (12) 18 Gross benefits paid (99) (115) (19) (19) Net benefit obligation at December 31 1,251 1,351 210 227 Change in plan assets: Fair value of plan assets at January 1 984 931 108 105 Actual return on plan assets 87 108 4 11 Employer contributions 39 60 8 7 Plan participants’ contributions — — 5 4 Gross benefits paid (99) (115) (19) (19) Fair value of plan assets at December 31 1,011 984 106 108 Under funded status at December 31 ($240) ($367) ($104) ($119) Defined Benefit Pension Plans OPEB Plans Alliant Energy 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $13 $8 Current liabilities (2) (2) (8) (8) Pension and other benefit obligations (238) (365) (109) (119) Net amounts recognized at December 31 ($240) ($367) ($104) ($119) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $429 $533 $38 $54 Prior service credit (4) (5) (1) (1) $425 $528 $37 $53 Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $615 $581 $91 $86 Service cost 7 7 1 1 Interest cost 16 20 2 3 Plan participants’ contributions — — 2 1 Actuarial (gain) loss (23) 60 (4) 8 Gross benefits paid (48) (53) (8) (8) Net benefit obligation at December 31 567 615 84 91 Change in plan assets: Fair value of plan assets at January 1 453 436 74 72 Actual return on plan assets 40 51 4 7 Employer contributions 17 19 2 2 Plan participants’ contributions — — 2 1 Gross benefits paid (48) (53) (8) (8) Fair value of plan assets at December 31 462 453 74 74 Under funded status at December 31 ($105) ($162) ($10) ($17) Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $10 $4 Current liabilities — (1) (2) (2) Pension and other benefit obligations (105) (161) (18) (19) Net amounts recognized at December 31 ($105) ($162) ($10) ($17) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $180 $228 $13 $20 Prior service credit (1) (1) — — $179 $227 $13 $20 Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Change in benefit obligation: Net benefit obligation at January 1 $588 $550 $89 $85 Service cost 4 4 1 2 Interest cost 15 19 2 3 Plan participants’ contributions — — 2 2 Actuarial (gain) loss (18) 55 (5) 5 Gross benefits paid (43) (40) (8) (8) Net benefit obligation at December 31 546 588 81 89 Change in plan assets: Fair value of plan assets at January 1 436 406 18 17 Actual return on plan assets 39 48 — 2 Employer contributions 18 22 5 5 Plan participants’ contributions — — 2 2 Gross benefits paid (43) (40) (8) (8) Fair value of plan assets at December 31 450 436 17 18 Under funded status at December 31 ($96) ($152) ($64) ($71) Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Amounts recognized on the balance sheets consist of: Non-current assets $— $— $3 $3 Current liabilities — — (6) (6) Pension and other benefit obligations (96) (152) (61) (68) Net amounts recognized at December 31 ($96) ($152) ($64) ($71) Amounts recognized in Regulatory Assets consist of: Net actuarial loss $188 $233 $18 $25 Prior service credit (1) (1) (1) (1) $187 $232 $17 $24
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 2021 2020 2021 2020 Accumulated benefit obligations $1,214 $1,305 $210 $227 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 1,214 1,305 210 227 Fair value of plan assets 1,011 984 106 108 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 1,251 1,351 N/A N/A Fair value of plan assets 1,011 984 N/A N/A Defined Benefit Pension Plans OPEB Plans IPL 2021 2020 2021 2020 Accumulated benefit obligations $546 $589 $84 $91 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 546 589 84 91 Fair value of plan assets 462 453 74 74 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 567 615 N/A N/A Fair value of plan assets 462 453 N/A N/A Defined Benefit Pension Plans OPEB Plans WPL 2021 2020 2021 2020 Accumulated benefit obligations $532 $573 $81 $89 Plans with accumulated benefit obligations in excess of plan assets: Accumulated benefit obligations 532 573 81 89 Fair value of plan assets 450 436 17 18 Plans with projected benefit obligations in excess of plan assets: Projected benefit obligations 546 588 N/A N/A Fair value of plan assets 450 436 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 2021 2020 2021 2020 Regulatory assets $35 $44 $30 $34
Estimated Future Employer Contributions	Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2022 is as follows (in millions): Alliant Energy IPL WPL Defined benefit pension plans (a) $2 $— $— 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 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $85 $83 $82 $82 $83 $387 OPEB 18 17 17 17 16 71 $103 $100 $99 $99 $99 $458 IPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $41 $40 $39 $39 $38 $174 OPEB 7 7 7 7 7 28 $48 $47 $46 $46 $45 $202 WPL 2022 2023 2024 2025 2026 2027 - 2031 Defined benefit pension benefits $37 $36 $35 $35 $34 $163 OPEB 7 7 7 7 6 27 $44 $43 $42 $42 $40 $190
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 Compensation expense $14 $16 $26 $8 $9 $15 $6 $6 $10 Income tax benefits 4 4 7 2 2 4 2 2 3
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, 2021, 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% 3% Equity securities - U.S. 14% - 54% 34% Equity securities - international 11% - 31% 21% Global asset securities 5% - 15% 9% Fixed income securities 25% - 45% 33% At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $35 $— $35 $— $46 $— $46 $— Equity securities - U.S. 256 256 — — 182 182 — — Equity securities - international — — — — 151 151 — — Global asset securities 52 52 — — 45 45 — — Fixed income securities 191 47 144 — 134 56 78 — Total assets in fair value hierarchy 534 $355 $179 $— 558 $434 $124 $— Assets measured at net asset value 477 426 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) (1) (1) Total pension plan assets $1,011 $984 2021 2020 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $21 $— $21 $— Equity securities - U.S. 117 117 — — 84 84 — — Equity securities - international — — — — 69 69 — — Global asset securities 24 24 — — 21 21 — — Fixed income securities 87 21 66 — 62 26 36 — Total assets in fair value hierarchy 244 $162 $82 $— 257 $200 $57 $— Assets measured at net asset value 218 196 Total pension plan assets $462 $453 2021 2020 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $20 $— $20 $— Equity securities - U.S. 114 114 — — 81 81 — — Equity securities - international — — — — 67 67 — — Global asset securities 23 23 — — 20 20 — — Fixed income securities 85 21 64 — 59 25 34 — Total assets in fair value hierarchy 238 $158 $80 $— 247 $193 $54 $— Assets measured at net asset value 212 189 Total pension plan assets $450 $436
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, 2021, 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% 3% Equity securities - U.S. 14% - 54% 34% Equity securities - international 11% - 31% 21% Global asset securities 5% - 15% 9% Fixed income securities 25% - 45% 33% At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $35 $— $35 $— $46 $— $46 $— Equity securities - U.S. 256 256 — — 182 182 — — Equity securities - international — — — — 151 151 — — Global asset securities 52 52 — — 45 45 — — Fixed income securities 191 47 144 — 134 56 78 — Total assets in fair value hierarchy 534 $355 $179 $— 558 $434 $124 $— Assets measured at net asset value 477 426 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) (1) (1) Total pension plan assets $1,011 $984 2021 2020 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $21 $— $21 $— Equity securities - U.S. 117 117 — — 84 84 — — Equity securities - international — — — — 69 69 — — Global asset securities 24 24 — — 21 21 — — Fixed income securities 87 21 66 — 62 26 36 — Total assets in fair value hierarchy 244 $162 $82 $— 257 $200 $57 $— Assets measured at net asset value 218 196 Total pension plan assets $462 $453 2021 2020 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $20 $— $20 $— Equity securities - U.S. 114 114 — — 81 81 — — Equity securities - international — — — — 67 67 — — Global asset securities 23 23 — — 20 20 — — Fixed income securities 85 21 64 — 59 25 34 — Total assets in fair value hierarchy 238 $158 $80 $— 247 $193 $54 $— Assets measured at net asset value 212 189 Total pension plan assets $450 $436
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, 2021, 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% 3% Equity securities - U.S. 14% - 54% 34% Equity securities - international 11% - 31% 21% Global asset securities 5% - 15% 9% Fixed income securities 25% - 45% 33% At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $35 $— $35 $— $46 $— $46 $— Equity securities - U.S. 256 256 — — 182 182 — — Equity securities - international — — — — 151 151 — — Global asset securities 52 52 — — 45 45 — — Fixed income securities 191 47 144 — 134 56 78 — Total assets in fair value hierarchy 534 $355 $179 $— 558 $434 $124 $— Assets measured at net asset value 477 426 Accrued investment income 1 1 Due to brokers, net (pending trades with brokers) (1) (1) Total pension plan assets $1,011 $984 2021 2020 Fair Level Level Level Fair Level Level Level IPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $21 $— $21 $— Equity securities - U.S. 117 117 — — 84 84 — — Equity securities - international — — — — 69 69 — — Global asset securities 24 24 — — 21 21 — — Fixed income securities 87 21 66 — 62 26 36 — Total assets in fair value hierarchy 244 $162 $82 $— 257 $200 $57 $— Assets measured at net asset value 218 196 Total pension plan assets $462 $453 2021 2020 Fair Level Level Level Fair Level Level Level WPL Value 1 2 3 Value 1 2 3 Cash and equivalents $16 $— $16 $— $20 $— $20 $— Equity securities - U.S. 114 114 — — 81 81 — — Equity securities - international — — — — 67 67 — — Global asset securities 23 23 — — 20 20 — — Fixed income securities 85 21 64 — 59 25 34 — Total assets in fair value hierarchy 238 $158 $80 $— 247 $193 $54 $— Assets measured at net asset value 212 189 Total pension plan assets $450 $436
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, 2021, 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): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $5 $— $5 $— $2 $— $2 $— Equity securities - U.S. 11 11 — — 4 4 — — Equity securities - international — — — — 3 3 — — Global asset securities 1 1 — — — — — — Fixed income securities 60 58 2 — 72 71 1 — Total assets in fair value hierarchy 77 $70 $7 $— 81 $78 $3 $— Assets measured at net asset value 29 27 Total OPEB plan assets $106 $108 2021 2020 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. 8 8 — — — — — — Fixed income securities 42 42 — — 51 51 — — Total assets in fair value hierarchy 51 $50 $1 $— 52 $51 $1 $— Assets measured at net asset value 23 22 Total OPEB plan assets $74 $74 2021 2020 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 — — — — — — Fixed income securities 15 15 — — 18 18 — — Total OPEB plan assets $17 $16 $1 $— $18 $18 $— $—
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, 2021, 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): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $5 $— $5 $— $2 $— $2 $— Equity securities - U.S. 11 11 — — 4 4 — — Equity securities - international — — — — 3 3 — — Global asset securities 1 1 — — — — — — Fixed income securities 60 58 2 — 72 71 1 — Total assets in fair value hierarchy 77 $70 $7 $— 81 $78 $3 $— Assets measured at net asset value 29 27 Total OPEB plan assets $106 $108 2021 2020 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. 8 8 — — — — — — Fixed income securities 42 42 — — 51 51 — — Total assets in fair value hierarchy 51 $50 $1 $— 52 $51 $1 $— Assets measured at net asset value 23 22 Total OPEB plan assets $74 $74 2021 2020 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 — — — — — — Fixed income securities 15 15 — — 18 18 — — Total OPEB plan assets $17 $16 $1 $— $18 $18 $— $—
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, 2021, 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): 2021 2020 Fair Level Level Level Fair Level Level Level Alliant Energy Value 1 2 3 Value 1 2 3 Cash and equivalents $5 $— $5 $— $2 $— $2 $— Equity securities - U.S. 11 11 — — 4 4 — — Equity securities - international — — — — 3 3 — — Global asset securities 1 1 — — — — — — Fixed income securities 60 58 2 — 72 71 1 — Total assets in fair value hierarchy 77 $70 $7 $— 81 $78 $3 $— Assets measured at net asset value 29 27 Total OPEB plan assets $106 $108 2021 2020 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. 8 8 — — — — — — Fixed income securities 42 42 — — 51 51 — — Total assets in fair value hierarchy 51 $50 $1 $— 52 $51 $1 $— Assets measured at net asset value 23 22 Total OPEB plan assets $74 $74 2021 2020 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 — — — — — — Fixed income securities 15 15 — — 18 18 — — Total OPEB plan assets $17 $16 $1 $— $18 $18 $— $—
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 2021 2020 2019 2021 2020 2019 2021 2020 2019 401(k) costs $26 $25 $25 $13 $13 $13 $12 $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 2021 2020 2019 2021 2020 2019 2021 2020 2019 401(k) costs $26 $25 $25 $13 $13 $13 $12 $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 2021 2020 2019 2021 2020 2019 2021 2020 2019 401(k) costs $26 $25 $25 $13 $13 $13 $12 $12 $12
Performance Shares Equity Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of the 2021, 2020 and 2019 performance shares activity, with amounts representing the target number of awards, was as follows: 2021 2020 2019 Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Performance Shares - Equity Weighted Average Grant Date Fair Value Nonvested awards, January 1 129,156 $54.63 74,193 $47.44 — $— Granted 73,112 46.19 56,204 64.04 91,816 47.23 Forfeited (5,839) 51.07 (1,241) 50.94 (17,623) 46.35 Nonvested awards, December 31 196,429 51.59 129,156 54.63 74,193 47.44
Performance Shares and Performance Units Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of these performance shares and performance units activity, with amounts representing the target number of awards, was as follows: Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 Nonvested awards, January 1 68,307 131,872 203,188 16,801 34,574 57,761 Vested (68,307) (63,565) (66,322) (16,801) (16,661) (20,131) Forfeited — — (4,994) — (1,112) (3,056) Nonvested awards, December 31 — 68,307 131,872 — 16,801 34,574 Performance Shares (granted prior to 2019) Performance Units (granted prior to 2019) 2021 2020 2019 2021 2020 2019 2018 Grant 2017 Grant 2016 Grant 2018 Grant 2017 Grant 2016 Grant Performance awards vested 68,307 63,565 66,322 16,801 16,661 20,131 Percentage of target number of performance awards 172.5% 155.0% 142.5% 172.5% 155.0% 142.5% Aggregate payout value (in millions) $7 $6 $4 $2 $2 $1 Payout - cash (in millions) $5 $5 $4 $2 $2 $1 Payout - common stock shares issued 13,644 9,543 6,447 N/A N/A N/A
Restricted Stock Units Equity Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of the 2021, 2020 and 2019 restricted stock units activity was as follows: 2021 2020 2019 Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Restricted Stock Units - Equity Weighted Average Grant Date Fair Value Nonvested units, January 1 146,549 $51.54 89,281 $46.04 — $— Granted 80,152 48.65 61,056 59.42 105,348 45.98 Forfeited (8,882) 49.84 (3,788) 49.01 (16,067) 45.63 Nonvested units, December 31 217,819 50.54 146,549 51.54 89,281 46.04
Restricted Stock Unit Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Equity-based Compensation Plans Activity	A summary of the restricted stock units granted prior to 2019 activity was as follows: 2021 2020 2019 Nonvested units, January 1 58,550 113,033 174,163 Vested (58,550) (54,483) (56,849) Forfeited — — (4,281) Nonvested units, December 31 — 58,550 113,033
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: 2021 2020 2019 Units Weighted Average Units Weighted Average Units Weighted Average Nonvested units, January 1 197,463 $47.31 206,065 $41.50 203,188 $37.23 Granted 73,112 48.66 56,204 59.37 91,816 46.10 Vested (68,307) 38.60 (63,565) 39.12 (66,322) 33.93 Forfeited (5,839) 50.46 (1,241) 49.25 (22,617) 44.00 Nonvested units, December 31 196,429 50.74 197,463 47.31 206,065 41.50

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2021 2020 2021 2020 Balance, January 1 $251 $196 $177 $134 $74 $62 Revisions in estimated cash flows 50 13 44 9 6 4 Liabilities settled (17) (13) (13) (9) (4) (4) Liabilities incurred 3 48 — 38 3 10 Accretion expense 7 7 5 5 2 2 Balance, December 31 $294 $251 $213 $177 $81 $74
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 2021 2020 2021 2020 2021 2020 Balance, January 1 $251 $196 $177 $134 $74 $62 Revisions in estimated cash flows 50 13 44 9 6 4 Liabilities settled (17) (13) (13) (9) (4) (4) Liabilities incurred 3 48 — 38 3 10 Accretion expense 7 7 5 5 2 2 Balance, December 31 $294 $251 $213 $177 $81 $74
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 2021 2020 2021 2020 2021 2020 Balance, January 1 $251 $196 $177 $134 $74 $62 Revisions in estimated cash flows 50 13 44 9 6 4 Liabilities settled (17) (13) (13) (9) (4) (4) Liabilities incurred 3 48 — 38 3 10 Accretion expense 7 7 5 5 2 2 Balance, December 31 $294 $251 $213 $177 $81 $74

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2021
Derivative [Line Items]
Notional Amounts of Derivative Instruments	As of December 31, 2021, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 9,135 2022 191,670 2022-2030 3,193 2022-2023 3,024 2022 IPL 2,647 2022 100,560 2022-2030 1,270 2022-2023 — — WPL 6,488 2022 91,110 2022-2030 1,923 2022-2023 3,024 2022
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 2021 2020 2021 2020 2021 2020 Current derivative assets $113 $24 $48 $20 $65 $4 Non-current derivative assets 63 10 36 9 27 1 Current derivative liabilities 8 9 4 3 4 6 Non-current derivative liabilities 1 16 — 9 1 7
IPL [Member]
Derivative [Line Items]
Notional Amounts of Derivative Instruments	As of December 31, 2021, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 9,135 2022 191,670 2022-2030 3,193 2022-2023 3,024 2022 IPL 2,647 2022 100,560 2022-2030 1,270 2022-2023 — — WPL 6,488 2022 91,110 2022-2030 1,923 2022-2023 3,024 2022
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 2021 2020 2021 2020 2021 2020 Current derivative assets $113 $24 $48 $20 $65 $4 Non-current derivative assets 63 10 36 9 27 1 Current derivative liabilities 8 9 4 3 4 6 Non-current derivative liabilities 1 16 — 9 1 7
WPL [Member]
Derivative [Line Items]
Notional Amounts of Derivative Instruments	As of December 31, 2021, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands): FTRs Natural Gas Coal Diesel Fuel MWhs Years Dths Years Tons Years Gallons Years Alliant Energy 9,135 2022 191,670 2022-2030 3,193 2022-2023 3,024 2022 IPL 2,647 2022 100,560 2022-2030 1,270 2022-2023 — — WPL 6,488 2022 91,110 2022-2030 1,923 2022-2023 3,024 2022
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 2021 2020 2021 2020 2021 2020 Current derivative assets $113 $24 $48 $20 $65 $4 Non-current derivative assets 63 10 36 9 27 1 Current derivative liabilities 8 9 4 3 4 6 Non-current derivative liabilities 1 16 — 9 1 7

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 176 — 146 30 176 34 — 5 29 34 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 9 — 8 1 9 25 — 25 — 25 Long-term debt (incl. current maturities) 7,368 — 8,329 1 8,330 6,777 — 8,107 2 8,109 IPL 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 84 — 65 19 84 29 — 3 26 29 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 4 — 3 1 4 12 — 12 — 12 Long-term debt 3,643 — 4,124 — 4,124 3,345 — 4,021 — 4,021 WPL 2021 2020 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $92 $— $81 $11 $92 $5 $— $2 $3 $5 Liabilities and equity: Derivatives 5 — 5 — 5 13 — 13 — 13 Long-term debt (incl. current maturities) 2,429 — 2,862 — 2,862 2,130 — 2,690 — 2,690
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 2021 2020 2021 2020 Beginning balance, January 1 $29 $21 $188 $188 Total net gains included in changes in net assets (realized/unrealized) 6 11 — — Purchases 21 14 — — Sales (1) (1) — — Settlements (a) (26) (16) 26 — Ending balance, December 31 $29 $29 $214 $188 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $6 $11 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2021 2020 2021 2020 Beginning balance, January 1 $26 $18 $188 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (3) 10 — — Purchases 16 11 — — Sales (1) (1) — — Settlements (a) (20) (12) 26 — Ending balance, December 31 $18 $26 $214 $188 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 ($3) $10 $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2021 2020 Beginning balance, January 1 $3 $3 Total net gains included in changes in net assets (realized/unrealized) 9 1 Purchases 5 3 Settlements (6) (4) Ending balance, December 31 $11 $3 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $9 $1 (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2021 $9 $20 $8 $10 $1 $10 2020 18 11 17 9 1 2
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 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 176 — 146 30 176 34 — 5 29 34 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 9 — 8 1 9 25 — 25 — 25 Long-term debt (incl. current maturities) 7,368 — 8,329 1 8,330 6,777 — 8,107 2 8,109 IPL 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 84 — 65 19 84 29 — 3 26 29 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 4 — 3 1 4 12 — 12 — 12 Long-term debt 3,643 — 4,124 — 4,124 3,345 — 4,021 — 4,021 WPL 2021 2020 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $92 $— $81 $11 $92 $5 $— $2 $3 $5 Liabilities and equity: Derivatives 5 — 5 — 5 13 — 13 — 13 Long-term debt (incl. current maturities) 2,429 — 2,862 — 2,862 2,130 — 2,690 — 2,690
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 2021 2020 2021 2020 Beginning balance, January 1 $29 $21 $188 $188 Total net gains included in changes in net assets (realized/unrealized) 6 11 — — Purchases 21 14 — — Sales (1) (1) — — Settlements (a) (26) (16) 26 — Ending balance, December 31 $29 $29 $214 $188 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $6 $11 $— $— IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds 2021 2020 2021 2020 Beginning balance, January 1 $26 $18 $188 $188 Total net gains (losses) included in changes in net assets (realized/unrealized) (3) 10 — — Purchases 16 11 — — Sales (1) (1) — — Settlements (a) (20) (12) 26 — Ending balance, December 31 $18 $26 $214 $188 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 ($3) $10 $— $— WPL Commodity Contract Derivative Assets and (Liabilities), net 2021 2020 Beginning balance, January 1 $3 $3 Total net gains included in changes in net assets (realized/unrealized) 9 1 Purchases 5 3 Settlements (6) (4) Ending balance, December 31 $11 $3 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $9 $1 (a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2021 $9 $20 $8 $10 $1 $10 2020 18 11 17 9 1 2
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 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 176 — 146 30 176 34 — 5 29 34 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 9 — 8 1 9 25 — 25 — 25 Long-term debt (incl. current maturities) 7,368 — 8,329 1 8,330 6,777 — 8,107 2 8,109 IPL 2021 2020 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 $32 $32 $— $— $32 $44 $44 $— $— $44 Derivatives 84 — 65 19 84 29 — 3 26 29 Deferred proceeds 214 — — 214 214 188 — — 188 188 Liabilities and equity: Derivatives 4 — 3 1 4 12 — 12 — 12 Long-term debt 3,643 — 4,124 — 4,124 3,345 — 4,021 — 4,021 WPL 2021 2020 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Derivatives $92 $— $81 $11 $92 $5 $— $2 $3 $5 Liabilities and equity: Derivatives 5 — 5 — 5 13 — 13 — 13 Long-term debt (incl. current maturities) 2,429 — 2,862 — 2,862 2,130 — 2,690 — 2,690
Fair Value Of Net Derivative Assets (Liabilities)	The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs 2021 $9 $20 $8 $10 $1 $10 2020 18 11 17 9 1 2

Commitments And Contingencies (

Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Long-term Purchase Commitment [Line Items]
Other Purchase Commitments	At December 31, 2021, the related minimum future commitments were as follows (in millions): Alliant Energy 2022 2023 2024 2025 2026 Thereafter Total Natural gas $307 $196 $144 $102 $88 $175 $1,012 Coal 63 46 25 3 — — 137 Other (a) 82 14 8 5 2 25 136 $452 $256 $177 $110 $90 $200 $1,285 IPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $148 $108 $84 $52 $42 $65 $499 Coal 32 27 17 3 — — 79 Other (a) 34 4 2 2 2 23 67 $214 $139 $103 $57 $44 $88 $645 WPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $159 $88 $60 $50 $46 $110 $513 Coal 31 19 8 — — — 58 Other (a) 33 1 1 1 1 — 37 $223 $108 $69 $51 $47 $110 $608 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2021.
Schedule of Environmental Liabilities	At December 31, 2021, 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, 2021, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $8 - $24 $6 - $18 Current and non-current environmental liabilities 11 8
IPL [Member]
Long-term Purchase Commitment [Line Items]
Other Purchase Commitments	At December 31, 2021, the related minimum future commitments were as follows (in millions): Alliant Energy 2022 2023 2024 2025 2026 Thereafter Total Natural gas $307 $196 $144 $102 $88 $175 $1,012 Coal 63 46 25 3 — — 137 Other (a) 82 14 8 5 2 25 136 $452 $256 $177 $110 $90 $200 $1,285 IPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $148 $108 $84 $52 $42 $65 $499 Coal 32 27 17 3 — — 79 Other (a) 34 4 2 2 2 23 67 $214 $139 $103 $57 $44 $88 $645 WPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $159 $88 $60 $50 $46 $110 $513 Coal 31 19 8 — — — 58 Other (a) 33 1 1 1 1 — 37 $223 $108 $69 $51 $47 $110 $608 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2021.
Schedule of Environmental Liabilities	At December 31, 2021, 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, 2021, such amounts for WPL were not material. Alliant Energy IPL Range of estimated future costs $8 - $24 $6 - $18 Current and non-current environmental liabilities 11 8
WPL [Member]
Long-term Purchase Commitment [Line Items]
Other Purchase Commitments	At December 31, 2021, the related minimum future commitments were as follows (in millions): Alliant Energy 2022 2023 2024 2025 2026 Thereafter Total Natural gas $307 $196 $144 $102 $88 $175 $1,012 Coal 63 46 25 3 — — 137 Other (a) 82 14 8 5 2 25 136 $452 $256 $177 $110 $90 $200 $1,285 IPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $148 $108 $84 $52 $42 $65 $499 Coal 32 27 17 3 — — 79 Other (a) 34 4 2 2 2 23 67 $214 $139 $103 $57 $44 $88 $645 WPL 2022 2023 2024 2025 2026 Thereafter Total Natural gas $159 $88 $60 $50 $46 $110 $513 Coal 31 19 8 — — — 58 Other (a) 33 1 1 1 1 — 37 $223 $108 $69 $51 $47 $110 $608 (a) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2021.

Segments Of Business (Tables)

Segments Of Business (Tables)	12 Months Ended
	Dec. 31, 2021
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 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 ATC Holdings, Utility Non-utility, Alliant Energy 2019 Electric Gas Other Total Parent and Other Consolidated Revenues $3,064 $455 $46 $3,565 $83 $3,648 Depreciation and amortization 513 47 3 563 4 567 Operating income 679 70 1 750 28 778 Interest expense 229 44 273 Equity income from unconsolidated investments, net (1) — — (1) (52) (53) Income tax expense (benefit) 73 (4) 69 Net income attributable to Alliant Energy common shareowners 517 40 557 Total assets 13,659 1,269 856 15,784 917 16,701 Investments in equity method subsidiaries 9 — — 9 449 458 Construction and acquisition expenditures 1,439 100 — 1,539 101 1,640
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): 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 2019 Electric Gas Other Total Revenues $1,781 $264 $44 $2,089 Depreciation and amortization 295 29 3 327 Operating income 360 39 4 403 Interest expense 127 Income taxes 24 Net income available for common stock 284 Total assets 8,075 734 468 9,277 Construction and acquisition expenditures 964 56 — 1,020
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): 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 2019 Electric Gas Other Total Revenues $1,283 $191 $2 $1,476 Depreciation and amortization 218 18 — 236 Operating income (loss) 319 31 (3) 347 Interest expense 102 Income taxes 49 Net income 233 Total assets 5,584 535 388 6,507 Construction and acquisition expenditures 475 44 — 519

Related Parties (Tables)

Related Parties (Tables)	12 Months Ended
	Dec. 31, 2021
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 2021 2020 2019 2021 2020 2019 Corporate Services billings $180 $176 $185 $154 $142 $142 Sales credited 22 35 68 23 3 7 Purchases billed 441 329 331 116 108 120
Net Intercompany Payables	As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2021 2020 IPL $110 $110 WPL 83 73
Related Amounts Billed Between Parties	The related amounts billed between the parties were as follows (in millions): 2021 2020 2019 ATC billings to WPL $122 $108 $109 WPL billings to ATC 18 10 13
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 2021 2020 2019 2021 2020 2019 Corporate Services billings $180 $176 $185 $154 $142 $142 Sales credited 22 35 68 23 3 7 Purchases billed 441 329 331 116 108 120
Net Intercompany Payables	As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2021 2020 IPL $110 $110 WPL 83 73
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 2021 2020 2019 2021 2020 2019 Corporate Services billings $180 $176 $185 $154 $142 $142 Sales credited 22 35 68 23 3 7 Purchases billed 441 329 331 116 108 120
Net Intercompany Payables	As of December 31, net intercompany payables to Corporate Services were as follows (in millions): 2021 2020 IPL $110 $110 WPL 83 73
Related Amounts Billed Between Parties	The related amounts billed between the parties were as follows (in millions): 2021 2020 2019 ATC billings to WPL $122 $108 $109 WPL billings to ATC 18 10 13

Condensed Parent Company Fina_2

Condensed Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2021
Condensed Financial Information Disclosure [Abstract]
Condensed Statements of Income	ALLIANT ENERGY CORPORATION (Parent Company Only) Year Ended December 31, CONDENSED STATEMENTS OF INCOME 2021 2020 2019 (in millions) Operating expenses $5 $7 $2 Operating loss (5) (7) (2) Other (income) and deductions: Equity earnings from consolidated subsidiaries (664) (625) (562) Interest expense 1 2 9 Other 1 4 7 Total other (income) and deductions (662) (619) (546) Income before income taxes 657 612 544 Income tax benefit (5) (4) (15) Net income $662 $616 $559 Refer to accompanying Notes to Condensed Financial Statements.
Condensed Balance Sheets	ALLIANT ENERGY CORPORATION (Parent Company Only) December 31, CONDENSED BALANCE SHEETS 2021 2020 (in millions) ASSETS Current assets: Notes receivable from affiliated companies $16 $32 Other 5 5 Total current assets 21 37 Investments: Investments in consolidated subsidiaries 7,061 6,664 Other 2 2 Total investments 7,063 6,666 Other assets 96 88 Total assets $7,180 $6,791 LIABILITIES AND EQUITY Current liabilities: Commercial paper $279 $132 Notes payable to affiliated companies 900 937 Other 4 29 Total current liabilities 1,183 1,098 Other liabilities 2 2 Common equity: Common stock and additional paid-in capital 2,752 2,706 Retained earnings 3,255 2,996 Shares in deferred compensation trust (12) (11) Total common equity 5,995 5,691 Total liabilities and equity $7,180 $6,791 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 2021 2020 2019 (in millions) Net cash flows from operating activities $494 $396 $305 Cash flows used for investing activities: Capital contributions to consolidated subsidiaries (295) (429) (250) Net change in notes receivable from and payable to affiliates (21) 201 8 Dividends from consolidated subsidiaries in excess of equity earnings 50 — — Net cash flows used for investing activities (266) (228) (242) Cash flows used for financing activities: Common stock dividends (403) (377) (338) Proceeds from issuance of common stock, net 28 247 390 Net change in commercial paper 147 (37) (116) Other — (1) 1 Net cash flows used for financing activities (228) (168) (63) 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 ($1) ($2) ($9) Income taxes, net 4 10 14 Refer to accompanying Notes to Condensed Financial Statements.

Summary Of Significant Accoun_4

Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)customerMW	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Cash, Cash Equivalents and Restricted Cash [Abstract]
Money market fund investments	$ 32	$ 44
Money market fund investments interest rate, percentage	0.04%
Current and Expected Credit Loss Estimates:
Adoption of new accounting standard, net of tax	$ (3,250)	(2,994)
Cumulative Effect, Period of Adoption, Adjustment [Member]
Current and Expected Credit Loss Estimates:
New accounting standard, cumulative effect adjustment to retained earnings, pre-tax			$ 12
Adoption of new accounting standard, net of tax			$ 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
Cash, Cash Equivalents and Restricted Cash [Abstract]
Money market fund investments	$ 32	44
Money market fund investments interest rate, percentage	0.04%
Property, Plant and Equipment:
AFUDC accrual recorded, percentage of estimated CWIP	100.00%
Current and Expected Credit Loss Estimates:
Adoption of new accounting standard, net of tax	$ (929)	(979)
WPL [Member]
Property, Plant and Equipment:
AFUDC accrual recorded, percentage of estimated CWIP	50.00%
AFUDC rates, projects with approval	100.00%
Current and Expected Credit Loss Estimates:
Adoption of new accounting standard, net of tax	$ (1,053)	$ (953)
Alliant Energy Finance, LLC [Member]
General:
Ownership interest	50.00%
Electric capacity of wind farm (in megawatts) | MW	225
Sheboygan Falls Energy Facility [Member]
General:
Fossil-fueled EGU capacity (in megawatts) | MW	347
Finance lease, lease term	20 years

Summary Of Significant Accoun_5

Summary Of Significant Accounting Policies (Schedule Of Average Rates Of Depreciation) (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Electric - generation [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.40%	3.50%	3.80%
Electric - generation [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	3.50%	3.50%	3.60%
Electric - distribution [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.90%	2.80%	2.90%
Electric - distribution [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	2.60%	2.60%	2.60%
Electric - other [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	5.70%	5.20%	5.30%
Electric - other [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	7.40%	6.10%	5.80%
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%	2.50%
Other [Member] | IPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	6.10%	6.30%	5.90%
Other [Member] | WPL [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Average rate of depreciation	5.40%	5.90%	5.60%

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, 2021	Dec. 31, 2020	Dec. 31, 2019
IPL [Member] | IPL (Wind generation CWIP) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	7.00%	7.10%	7.40%
IPL [Member] | IPL (other CWIP) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	7.20%	7.20%	7.50%
WPL [Member] | WPL (retail jurisdiction) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	7.00%	7.00%	6.80%
WPL [Member] | WPL (wholesale jurisdiction) [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Recovery rates	5.60%	6.30%	6.90%

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2020USD ($)	Aug. 31, 2020customer	Dec. 31, 2021USD ($)MW	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Regulatory Matters [Line Items]
Regulatory assets			$ 1,940	$ 2,010
Credits issued to customers			(66)	(113)	$ (40)
Regulatory liabilities			1,271	1,306
Electric transmission cost recovery [Member]
Regulatory Matters [Line Items]
Regulatory liabilities			51	68
IPL [Member]
Regulatory Matters [Line Items]
Regulatory assets not earning a return			75
Regulatory assets			1,443	1,483
Credits issued to customers			$ 1	(20)	2
Electric capacity of wind farm (in megawatts) | MW			1,000
Regulatory liabilities			$ 691	676
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Matters [Line Items]
Credits issued to customers				42
Regulatory liabilities			27	39
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			13
Regulatory assets			497	527
Credits issued to customers			(67)	(93)	(42)
Regulatory liabilities			580	630
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Matters [Line Items]
Regulatory liabilities			24	29
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 Electric [Member] | WPL [Member]
Regulatory Matters [Line Items]
Authorized increase (decrease) in final rates, amount				$ 29
Authorized increase (decrease) in final rates, percentage				2.00%
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
Deferred Fuel Costs | WPL [Member]
Regulatory Matters [Line Items]
Regulatory assets			$ 37
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, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets	$ 1,940	$ 2,010
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	934	890
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	462	580
AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	128	119
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	92	113
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	90	110
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	52	55
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	4
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	8	26
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	132	113
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,443	1,483
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	884	843
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	228	291
IPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	89	81
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	77
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	90	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	2	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	4	13
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	80	67
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	497	527
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	50	47
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	234	289
WPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	39	38
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	26	36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	52	55
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	40	3
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	4	13
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 52	$ 46

Regulatory Matters (Assets Reti

Regulatory Matters (Assets Retired Early) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets	$ 1,940	$ 2,010
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	92	113
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,443	1,483
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	77
IPL [Member] | Assets retired early [Member] | Sutherland Units 1 and 3 [Member]
Regulatory Assets [Line Items]
Regulatory assets	19
IPL [Member] | Assets retired early [Member] | M.L. Kapp Unit 2 [Member]
Regulatory Assets [Line Items]
Regulatory assets	18
IPL [Member] | Assets retired early [Member] | Analog Electric Meters [Member]
Regulatory Assets [Line Items]
Regulatory assets	29
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	497	527
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	26	$ 36
WPL [Member] | Assets retired early [Member] | Nelson Dewey Units 1 and 2 and Edgewater Unit 3 [Member]
Regulatory Assets [Line Items]
Regulatory assets	6
WPL [Member] | Assets retired early [Member] | Edgewater Unit 4 [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 20

Regulatory Matters (Regulator_2

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,271	$ 1,306
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	585	732
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	384	367
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	166	28
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	51	68
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	36	38
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	49	73
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	691	676
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	312	331
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	252	238
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	77	25
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	27	39
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	23	43
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	580	630
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	273	401
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	132	129
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	89	3
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	24	29
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	36	38
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 26	$ 30

Property, Plant and Equipment_2

Property, Plant and Equipment (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021
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, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	$ 2,094	$ 1,269
Total electric plant	16,710	16,243
Gas plant in service	1,636	1,563
Other plant in service	621	534
Accumulated depreciation	(5,263)	(4,868)
Net plant	13,704	13,472
Leased land for solar generation, net	11	0
Construction work in progress	778	405
Other, net	7	7
Total utility	14,500	13,884
Non-utility Generation, net	75	79
Corporate Services and other, net	412	373
Total non-utility and other	487	452
Total property, plant and equipment	14,987	14,336
Non-utility Generation, accumulated depreciation	67	63
Corporate Services and other, accumulated depreciation	245	210
Generation [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	7,539	8,222
Distribution [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	6,537	6,216
Other [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	540	536
IPL [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	487	459
Total electric plant	9,424	9,171
Gas plant in service	878	844
Other plant in service	398	354
Accumulated depreciation	(2,897)	(2,671)
Net plant	7,803	7,698
Construction work in progress	174	185
Other, net	6	6
Total utility	7,983	7,889
Total property, plant and equipment	7,983	7,889
IPL [Member] | Lansing [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	245
IPL [Member] | Generation [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	4,922	4,884
IPL [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	3,652	3,470
IPL [Member] | Other [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	363	358
WPL [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	1,607	810
Total electric plant	7,286	7,072
Gas plant in service	758	719
Other plant in service	223	180
Accumulated depreciation	(2,366)	(2,197)
Net plant	5,901	5,774
Leased Sheboygan Falls Energy Facility, net	21	27
Leased land for solar generation, net	11	0
Construction work in progress	604	220
Other, net	1	1
Total utility	6,538	6,022
Total property, plant and equipment	6,538	6,022
Leased Sheboygan Falls Energy Facility, accumulated depreciation	100	95
WPL [Member] | Edgewater Unit 5 [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	527
WPL [Member] | Columbia Units 1 And 2 [Member]
Property, Plant and Equipment [Line Items]
Electric plant anticipated to be retired early	460
WPL [Member] | Generation [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	2,617	3,338
WPL [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	2,885	2,746
WPL [Member] | Other [Member]
Property, Plant and Equipment [Line Items]
Electric plant in service	$ 177	$ 178

Property, Plant and Equipment_4

Property, Plant and Equipment (Equity and Debt AFUDC) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	$ 25	$ 55	$ 93
Equity [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	18	39	66
Debt [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	7	16	27
IPL [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	9	24	50
IPL [Member] | Equity [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	7	17	35
IPL [Member] | Debt [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	2	7	15
WPL [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	16	31	43
WPL [Member] | Equity [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	11	22	31
WPL [Member] | Debt [Member]
Property, Plant and Equipment [Line Items]
Allowance for funds used during construction	$ 5	$ 9	$ 12

Jointly-Owned Electric Utilit_3

Jointly-Owned Electric Utility Plant (Details) $ in Millions	Dec. 31, 2021USD ($)
Jointly Owned Electric Utility Plant [Line Items]
Electric Plant	$ 2,631
Accumulated Provision for Depreciation	806
Construction Work in Progress	25
IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Electric Plant	1,005
Accumulated Provision for Depreciation	411
Construction Work in Progress	16
WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Electric Plant	1,626
Accumulated Provision for Depreciation	395
Construction Work in Progress	$ 9
Ottumwa Unit 1 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	48.00%
Electric Plant	$ 599
Accumulated Provision for Depreciation	214
Construction Work in Progress	$ 11
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	100
Construction Work in Progress	$ 2
George Neal Unit 3 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	28.00%
Electric Plant	$ 173
Accumulated Provision for Depreciation	74
Construction Work in Progress	$ 3
Louisa Unit 1 [Member] | IPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	4.00%
Electric Plant	$ 40
Accumulated Provision for Depreciation	23
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	$ 802
Accumulated Provision for Depreciation	314
Construction Work in Progress	$ 6
West Riverside Energy Center and Solar Garden [Member] | WPL [Member]
Jointly Owned Electric Utility Plant [Line Items]
Ownership Interest %	91.00%
Electric Plant	$ 706
Accumulated Provision for Depreciation	33
Construction Work in Progress	$ 3
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	48
Construction Work in Progress	$ 0

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) $ in Millions	Dec. 31, 2021USD ($)
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	$ 109

Receivables (Details of Account

Receivables (Details of Accounts Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable [Line Items]
Customer	$ 93	$ 101
Unbilled utility revenues	91	82
Deferred proceeds	214	188
Other	53	59
Allowance for expected credit losses	(11)	(18)
Accounts receivable, less allowance for expected credit losses	440	412
IPL [Member]
Accounts Receivable [Line Items]
Customer	0	0
Unbilled utility revenues	0	0
Deferred proceeds	214	188
Other	28	23
Allowance for expected credit losses	(1)	(1)
Accounts receivable, less allowance for expected credit losses	241	210
WPL [Member]
Accounts Receivable [Line Items]
Customer	82	92
Unbilled utility revenues	91	82
Other	25	35
Allowance for expected credit losses	(10)	(17)
Accounts receivable, less allowance for expected credit losses	$ 188	$ 192

Receivables (Maximum And Averag

Receivables (Maximum And Average Outstanding Cash Proceeds) (Details) - IPL [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Maximum [Member]
Accounts Receivable [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 110	$ 96	$ 108
Average [Member]
Accounts Receivable [Line Items]
Outstanding aggregate cash proceeds (based on daily outstanding balances)	$ 46	$ 9	$ 36

Receivables (Receivables Sold U

Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable [Line Items]
Fair value of deferred proceeds	$ 214	$ 188
IPL [Member]
Accounts Receivable [Line Items]
Fair value of deferred proceeds	214	188
Financing Receivable [Member] | IPL [Member]
Accounts Receivable [Line Items]
Customer accounts receivable	125	114
Unbilled utility revenues	104	92
Receivables sold to third party	229	206
Less: cash proceeds	1	1
Deferred proceeds	228	205
Less: allowance for expected credit losses	14	17
Fair value of deferred proceeds	214	188
Financing Receivable [Member] | IPL [Member] | Financial Asset, Past Due
Accounts Receivable [Line Items]
Outstanding receivables past due	$ 22	$ 27

Receivables (Additional Attribu

Receivables (Additional Attributes Of Receivables Sold Under The Agreement) (Details) - IPL [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable [Line Items]
Collections	$ 2,134	$ 2,025	$ 2,193
Write-offs, net of recoveries	$ 9	$ 7	$ 19

Investments (Narrative) (Detail

Investments (Narrative) (Details)	Dec. 31, 2021
ATC LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	16.00%
ATC Holdco LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	20.00%

Investments (Unconsolidated Equ

Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Carrying value	$ 508	$ 476	$ 458
Equity (income) / loss	(62)	(61)	(53)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	338	331
Equity (income) / loss	$ (43)	(47)	(45)
ATC LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	16.00%
ATC Holdco LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	20.00%
Non-utility wind farm in Oklahoma [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%
Carrying value	$ 99	103
Equity (income) / loss	(4)	(8)	(5)
Corporate venture investments [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	52	31
Equity (income) / loss	(13)	(4)	(1)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	19	11
Equity (income) / loss	(2)	(2)	(2)
Total [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	508	476
Equity (income) / loss	$ (62)	$ (61)	$ (53)

Investments (Summary Financial

Investments (Summary Financial Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues	$ 3,669	$ 3,416	$ 3,648
Current assets	1,069	887
Current liabilities	2,054	1,297
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Revenues	802	801	783
Operating income	357	376	359
Net income	358	343	$ 340
Current assets	112	121
Non-current assets	7,036	6,388
Current liabilities	455	317
Non-current liabilities	3,110	2,997
Noncontrolling interest	$ 247	$ 192

Common Equity (Narrative) (Deta

Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Common Equity [Line Items]
Shares available for issuance under the 2020 OIP, Shareowner Direct Plan and 401(k) Savings Plan (in shares)	14,000,000
Proceeds from issuance of common stock, net	$ 28	$ 247	$ 390
Equity Forward Agreements [Member]
Schedule of Common Equity [Line Items]
Common stock issued during the period (in shares)	0	4,275,127	8,358,973
Proceeds from issuance of common stock, net		$ 222	$ 366
Initial forward sale price (in dollars per share)		$ 51.98	$ 43.75

Common Equity (Common Share Act

Common Equity (Common Share Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1 (in shares)	249,868,415	245,022,800	236,063,279
Common stock issued during the period, Shareowner Direct Plan (in shares)	492,565	472,283	501,808
Common stock issued during the period, Equity-based compensation plans (in shares)	113,549	98,205	101,478
Common stock issued during the period, Other (in shares)	0	0	(2,738)
Shares outstanding, December 31 (in shares)	250,474,529	249,868,415	245,022,800
Equity Forward Agreements [Member]
Common Stock Oustanding [Roll Forward]
Common stock issued during the period (in shares)	0	4,275,127	8,358,973

Preferred Stock (Narrative) (De

Preferred Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Payments to redeem cumulative preferred stock of IPL	$ 200	$ 0	$ 0
Cumulative Preferred Stock [Member] | 5.1% [Member]
Temporary Equity [Line Items]
Non-cash charge, preferred stock redemption	5
IPL [Member]
Temporary Equity [Line Items]
Payments to redeem cumulative preferred stock of IPL	$ 200	$ 0	$ 0
IPL [Member] | Cumulative Preferred Stock [Member]
Temporary Equity [Line Items]
Shares authorized (in shares)	16,000,000
IPL [Member] | Cumulative Preferred Stock [Member] | 5.1% [Member]
Temporary Equity [Line Items]
Shares authorized (in shares)		8,000,000
Shares outstanding (in shares)		8,000,000
Cumulative preferred stock rate		5.10%
Preferred stock redemption price per share (in dollars per share)		$ 25
Payments to redeem cumulative preferred stock of IPL	$ 200
Non-cash charge, preferred stock redemption	$ 5

Preferred Stock (Carrying Value

Preferred Stock (Carrying Value Of Cumulative Preferred Stock) (Details) - IPL [Member] - Cumulative Preferred Stock [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021
Temporary Equity [Line Items]
Shares Authorized (in shares)		16,000,000
5.1% [Member]
Temporary Equity [Line Items]
Series	5.10%
Liquidation Preference/Stated Value (in dollars per share)	$ 25
Shares Authorized (in shares)	8,000,000
Preferred Stock, Shares Outstanding	8,000,000
Cumulative preferred stock	$ 200

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		$ 1,000
Parent Company [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		450
IPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		250
WPL [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		$ 300
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, 2021	Dec. 31, 2020
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 515	$ 389
Weighted average interest rates	0.20%	0.20%
Available credit facility capacity	$ 485	$ 611
IPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	0	0
Available credit facility capacity	250	250
WPL [Member]
Commercial paper and borrowings under the single credit facility:
Amount outstanding	$ 236	$ 257
Weighted average interest rates	0.20%	0.10%
Available credit facility capacity	$ 64	$ 43

Debt (Other Short-Term Borrowin

Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 648	$ 495
Average amount outstanding (based on daily outstanding balances)	$ 459	$ 292
Weighted average interest rates	0.20%	0.70%
IPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 19	$ 8
Average amount outstanding (based on daily outstanding balances)	$ 0	$ 0
Weighted average interest rates	0.20%	0.50%
WPL [Member]
Debt Instrument [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 320	$ 266
Average amount outstanding (based on daily outstanding balances)	$ 172	$ 117
Weighted average interest rates	0.10%	0.70%

Debt (Long-term Debt) (Details)

Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 7,425	$ 6,833
Current maturities	(633)	(8)
Unamortized debt issuance costs	(42)	(41)
Unamortized debt (discount) and premium, net	(15)	(15)
Long-term debt, net	6,735	6,769
Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,675	3,375
Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500
Interest rate	3.25%	3.25%
Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	3.40%	3.40%
Senior Debentures [Member] | 5.5% senior debenture, due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50	$ 50
Interest rate	5.50%	5.50%
Senior Debentures [Member] | 4.1% senior debenture, due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500
Interest rate	4.10%	4.10%
Senior Debentures [Member] | 3.6% senior debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	3.60%	3.60%
Senior Debentures [Member] | 2.3% senior debenture, due 2030 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400
Interest rate	2.30%	2.30%
Senior Debentures [Member] | 6.45% senior debenture, due 2033 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100
Interest rate	6.45%	6.45%
Senior Debentures [Member] | 6.3% senior debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 125	$ 125
Interest rate	6.30%	6.30%
Senior Debentures [Member] | 6.25% senior debenture, due 2039 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	6.25%	6.25%
Senior Debentures [Member] | 4.7% senior debenture, due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	4.70%	4.70%
Senior Debentures [Member] | 3.7% senior debenture, due 2046 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	3.70%	3.70%
Senior Debentures [Member] | 3.5% senior debenture, due 2049 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	3.50%	3.50%
Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	3.10%
Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,450	$ 2,150
Debentures [Member] | 2.25% debenture, due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	2.25%	2.25%
Debentures [Member] | 3.05% debenture, due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	3.05%	3.05%
Debentures [Member] | 3% debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350
Interest rate	3.00%	3.00%
Debentures [Member] | 1.95% debenture, due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	1.95%
Debentures [Member] | 6.25% debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100
Interest rate	6.25%	6.25%
Debentures [Member] | 6.375% debenture, due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	6.375%	6.375%
Debentures [Member] | 7.6% debenture, due 2038 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	7.60%	7.60%
Debentures [Member] | 4.1% debenture, due 2044 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	4.10%	4.10%
Debentures [Member] | 3.65% debenture, due 2050 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350
Interest rate	3.65%	3.65%
Other Long Term Debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,300	$ 1,308
Other [Member] | Other, 1% at December 31, 2021, due 2022 to 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1	2
Interest rate	1.00%
IPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,675	3,375
Current maturities	0	0
Unamortized debt issuance costs	(23)	(22)
Unamortized debt (discount) and premium, net	(9)	(8)
Long-term debt, net	3,643	3,345
IPL [Member] | Senior Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	3,675	3,375
IPL [Member] | Senior Debentures [Member] | 3.25% senior debenture, due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 500	$ 500
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	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
Interest rate	3.50%	3.50%
IPL [Member] | Senior Debentures [Member] | 3.1% senior debenture, due 2051 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	3.10%
WPL [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,450	$ 2,150
Current maturities	(250)	0
Unamortized debt issuance costs	(15)	(14)
Unamortized debt (discount) and premium, net	(6)	(6)
Long-term debt, net	2,179	2,130
WPL [Member] | Debentures [Member]
Debt Instrument [Line Items]
Long-term debt	2,450	2,150
WPL [Member] | Debentures [Member] | 2.25% debenture, due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	2.25%	2.25%
WPL [Member] | Debentures [Member] | 3.05% debenture, due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	3.05%	3.05%
WPL [Member] | Debentures [Member] | 3% debenture, due 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350
Interest rate	3.00%	3.00%
WPL [Member] | Debentures [Member] | 1.95% debenture, due 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300
Interest rate	1.95%
WPL [Member] | Debentures [Member] | 6.25% debenture, due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 100	$ 100
Interest rate	6.25%	6.25%
WPL [Member] | Debentures [Member] | 6.375% debenture, due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	6.375%	6.375%
WPL [Member] | Debentures [Member] | 7.6% debenture, due 2038 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	7.60%	7.60%
WPL [Member] | Debentures [Member] | 4.1% debenture, due 2044 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 250	$ 250
Interest rate	4.10%	4.10%
WPL [Member] | Debentures [Member] | 3.65% debenture, due 2050 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 350	$ 350
Interest rate	3.65%	3.65%
Alliant Energy Finance, LLC [Member] | Term Loan Credit Agreement [Member] | Term loan credit agreement through March 2022
Debt Instrument [Line Items]
Long-term debt	$ 300	$ 300
Interest rate	1.00%
Alliant Energy Finance, LLC [Member] | Senior Notes [Member] | 3.75% senior notes, due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 400	$ 400
Interest rate	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
Interest rate	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
Interest rate	4.25%	4.25%
Corporate Services [Member] | Senior Notes [Member] | 3.45% senior notes, due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 75	$ 75
Interest rate	3.45%	3.45%
Sheboygan Power, LLC [Member] | Senior Secured Notes [Member] | 5.06% senior secured notes, due 2022 to 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 24	$ 31
Interest rate	5.06%	5.06%

Debt (Schedule Of Debt Maturiti

Debt (Schedule Of Debt Maturities) (Details) $ in Millions	Dec. 31, 2021USD ($)
2022	$ 633
2023	408
2024	509
2025	300
2026	200
IPL [Member]
2022	0
2023	0
2024	500
2025	300
2026	0
WPL [Member]
2022	250
2023	0
2024	0
2025	0
2026	0
Corporate Services [Member]
2022	75
2023	0
2024	0
2025	0
2026	0
Alliant Energy Finance, LLC [Member]
2022	308
2023	408
2024	9
2025	0
2026	$ 200

Leases (Narrative) (Details)

Leases (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021lease_renewal_period_option
Sheboygan Falls Energy Facility [Member] | WPL [Member]
Leases [Line Items]
Finance lease, renewal options (in number of renewal periods)	2

Leases (Operating Leases) (Deta

Leases (Operating Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 14	$ 15
Operating leases liabilities, Other current liabilities	2	2
Operating leases liabilities, Other liabilities	12	13
Operating leases liabilities, Total	$ 14	$ 15
Operating leases, Weighted average remaining lease term	9 years	10 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other	Other
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other	Other
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
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	4.00%	4.00%
WPL [Member]
Leases [Line Items]
Operating leases assets, Property, plant and equipment, net	$ 5	$ 6
Operating leases liabilities, Other current liabilities	1	1
Operating leases liabilities, Other liabilities	4	5
Operating leases liabilities, Total	$ 5	$ 6
Operating leases, Weighted average remaining lease term	8 years	9 years
Operating leases, Weighted average discount rate, percent	4.00%	4.00%

Leases (Finance Lease) (Details

Leases (Finance Lease) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 11
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance lease liabilities, Other current liabilities	$ 1
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other	Other
Finance lease liabilities, Other liabilities	$ 11
Finance lease liabilities, Total	$ 12
Finance lease, Weighted average remaining lease term	34 years
Finance lease, Weighted average discount rate, percent	3.00%
Finance lease, Depreciation and amortization expense	$ 0
Finance lease, Interest expense	0
Finance lease, Total expense	$ 0
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	$ 11
Finance lease liabilities, Other current liabilities	1
Finance lease liabilities, Other liabilities	11
WPL [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	32	$ 27
Finance lease liabilities, Other current liabilities	11	9
Finance lease liabilities, Other liabilities	42	42
Finance lease liabilities, Total	$ 53	$ 51
Finance lease, Weighted average remaining lease term	10 years	4 years
Finance lease, Weighted average discount rate, percent	9.00%	11.00%
Finance lease, Depreciation and amortization expense	$ 6	$ 6	$ 6
Finance lease, Interest expense	5	6	7
Finance lease, Total expense	11	12	$ 13
WPL [Member] | Sheboygan Falls Energy Facility [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	21	27
Finance lease liabilities, Other current liabilities	10	9
Finance lease liabilities, Other liabilities	31	42
WPL [Member] | Leased land for solar generation [Member]
Leases [Line Items]
Finance lease assets, Property, plant and equipment, net	11	0
Finance lease liabilities, Other current liabilities	1	0
Finance lease liabilities, Other liabilities	$ 11	$ 0

Leases (Expected Maturities of

Leases (Expected Maturities of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Leases [Line Items]
Operating Leases Liability, 2022	$ 2
Operating Leases Liability, 2023	2
Operating Leases Liability, 2024	2
Operating Leases Liability, 2025	2
Operating Leases Liability, 2026	2
Operating Leases Liability, Thereafter	7
Operating Leases Liability, Total	17
Operating Leases Liability, Less: amount representing interest	3
Operating Leases Liability, Present value of minimum lease payments	14	$ 15
Finance Lease Liability, 2022	0
Finance Lease Liability, 2023	0
Finance Lease Liability, 2024	0
Finance Lease Liability, 2025	0
Finance Lease Liability, 2026	1
Finance Lease Liability, Thereafter	19
Finance Lease Liability, Total	20
Finance Lease Liability, Less: amount representing interest	8
Finance Lease Liability, Present value of minimum lease payments	12
IPL [Member]
Leases [Line Items]
Operating Leases Liability, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, 2024	1
Operating Leases Liability, 2025	1
Operating Leases Liability, 2026	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, 2022	1
Operating Leases Liability, 2023	1
Operating Leases Liability, 2024	1
Operating Leases Liability, 2025	1
Operating Leases Liability, 2026	1
Operating Leases Liability, Thereafter	1
Operating Leases Liability, Total	6
Operating Leases Liability, Less: amount representing interest	1
Operating Leases Liability, Present value of minimum lease payments	5	6
Finance Lease Liability, 2022	15
Finance Lease Liability, 2023	15
Finance Lease Liability, 2024	15
Finance Lease Liability, 2025	6
Finance Lease Liability, 2026	1
Finance Lease Liability, Thereafter	19
Finance Lease Liability, Total	71
Finance Lease Liability, Less: amount representing interest	18
Finance Lease Liability, Present value of minimum lease payments	$ 53	$ 51

Disaggregation of Revenues (Det

Disaggregation of Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 3,669	$ 3,416	$ 3,648
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,063	1,947	2,089
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,523	1,395	1,476
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues	3,081	2,920	3,064
Electric [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,752	1,695	1,781
Electric [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,329	1,225	1,283
Electric [Member] | Retail - Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,115	1,093	1,092
Electric [Member] | Retail - Residential [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	620	602	601
Electric [Member] | Retail - Residential [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	495	491	491
Electric [Member] | Retail - Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues	763	718	770
Electric [Member] | Retail - Commercial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	508	474	510
Electric [Member] | Retail - Commercial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	255	244	260
Electric [Member] | Retail - Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	893	841	889
Electric [Member] | Retail - Industrial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	505	488	504
Electric [Member] | Retail - Industrial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	388	353	385
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenues	187	168	177
Electric [Member] | Wholesale [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	57	57	64
Electric [Member] | Wholesale [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	130	111	113
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	123	100	136
Electric [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	62	74	102
Electric [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	61	26	34
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues	456	373	455
Gas [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	265	208	264
Gas [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	191	165	191
Gas [Member] | Retail - Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	257	214	259
Gas [Member] | Retail - Residential [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	146	116	149
Gas [Member] | Retail - Residential [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	111	98	110
Gas [Member] | Retail - Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues	139	107	133
Gas [Member] | Retail - Commercial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	79	59	75
Gas [Member] | Retail - Commercial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	60	48	58
Gas [Member] | Retail - Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	17	12	16
Gas [Member] | Retail - Industrial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	12	8	12
Gas [Member] | Retail - Industrial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	5	4	4
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	43	40	47
Gas [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	28	25	28
Gas [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	15	15	19
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenues	49	49	46
Other Utility [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	46	44	44
Other Utility [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	3	5	2
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	13	13	9
Other Utility [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	10	8	7
Other Utility [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	3	5	2
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenues	36	36	37
Other Utility [Member] | Steam [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	36	36	37
Non-Utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	83	74	83
Non-Utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 83	$ 74	$ 83

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax [Line Items]
Overall income tax rate	(12.00%)	(10.00%)	11.00%
IPL [Member]
Income Tax [Line Items]
Overall income tax rate	(11.00%)	(16.00%)	8.00%
WPL [Member]
Income Tax [Line Items]
Overall income tax rate	(24.00%)	(8.00%)	17.00%
State [Member]
Income Tax [Line Items]
Overall income tax rate	9.80%	12.00%
State [Member] | IPL [Member]
Income Tax [Line Items]
Overall income tax rate	9.80%	12.00%
State [Member] | WPL [Member]
Income Tax [Line Items]
Overall income tax rate	9.80%	12.00%

Income Taxes (Schedule Of Compo

Income Taxes (Schedule Of Components Of Income Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current tax expense (benefit):
Federal	$ 1	$ 1	$ (7)
State	3	8	24
Deferred tax expense (benefit):
Federal	9	22	70
State	15	8	42
Production tax credits	(101)	(95)	(55)
Investment tax credits	(1)	(1)	(1)
Income tax expense (benefit)	(74)	(57)	69
IPL's tax benefit riders [Member]
Current tax expense (benefit):
IPL's tax benefit riders	0	0	(4)
IPL [Member]
Current tax expense (benefit):
Federal	(21)	6	(11)
State	(1)	(1)	24
Deferred tax expense (benefit):
Federal	73	30	26
State	0	(2)	31
Production tax credits	(87)	(80)	(42)
Investment tax credits	0	0	0
Income tax expense (benefit)	(36)	(47)	24
IPL [Member] | IPL's tax benefit riders [Member]
Current tax expense (benefit):
IPL's tax benefit riders	0	0	(4)
WPL [Member]
Current tax expense (benefit):
Federal	22	(11)	12
State	6	7	13
Deferred tax expense (benefit):
Federal	(75)	(9)	31
State	11	10	6
Production tax credits	(14)	(15)	(13)
Investment tax credits	(1)	(1)	0
Income tax expense (benefit)	$ (51)	$ (19)	$ 49

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	2.00%	2.00%	7.00%
Amortization of excess deferred taxes	(18.00%)	(13.00%)	(1.00%)
Production tax credits	(17.00%)	(17.00%)	(9.00%)
Effect of rate-making on property-related differences	(1.00%)	(3.00%)	(6.00%)
Adjustment for prior period taxes	1.00%	1.00%	1.00%
Other items, net	0.00%	(1.00%)	(1.00%)
Overall income tax rate	(12.00%)	(10.00%)	11.00%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	(1.00%)	(1.00%)	8.00%
Amortization of excess deferred taxes	(4.00%)	(5.00%)	0.00%
Production tax credits	(27.00%)	(28.00%)	(13.00%)
Effect of rate-making on property-related differences	(2.00%)	(4.00%)	(10.00%)
Adjustment for prior period taxes	2.00%	1.00%	3.00%
Other items, net	0.00%	0.00%	0.00%
Overall income tax rate	(11.00%)	(16.00%)	8.00%
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	6.00%	6.00%	6.00%
Amortization of excess deferred taxes	(43.00%)	(26.00%)	(2.00%)
Production tax credits	(6.00%)	(7.00%)	(5.00%)
Effect of rate-making on property-related differences	(1.00%)	(2.00%)	(3.00%)
Adjustment for prior period taxes	0.00%	0.00%	0.00%
Other items, net	(1.00%)	0.00%	0.00%
Overall income tax rate	(24.00%)	(8.00%)	17.00%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	0.00%	0.00%	(1.00%)
IPL's tax benefit riders [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	0.00%	0.00%	(1.00%)

Income Taxes (Schedule Of Defer

Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities, property	$ 2,389	$ 2,232
Deferred tax liabilities, other	111	101
Total deferred tax liabilities	2,623	2,449
Deferred tax assets, federal credit carryforwards	560	454
Deferred tax assets, net operating losses carryforwards - federal	39	77
Deferred tax assets, net operating losses carryforwards - state	38	37
Deferred tax assets, other	65	73
Subtotal deferred tax assets	702	641
Deferred tax assets, valuation allowances	(6)	(6)
Total deferred tax assets	696	635
Total deferred tax liabilities, net	1,927	1,814
IPL [Member]
Deferred tax liabilities, property	1,416	1,312
Deferred tax liabilities, other	76	83
Total deferred tax liabilities	1,492	1,395
Deferred tax assets, federal credit carryforwards	345	258
Deferred tax assets, net operating losses carryforwards - federal	36	71
Deferred tax assets, net operating losses carryforwards - state	3	1
Deferred tax assets, other	25	30
Subtotal deferred tax assets	409	360
Deferred tax assets, valuation allowances	0	0
Total deferred tax assets	409	360
Total deferred tax liabilities, net	1,083	1,035
WPL [Member]
Deferred tax liabilities, property	913	854
Deferred tax liabilities, other	50	41
Total deferred tax liabilities	963	895
Deferred tax assets, federal credit carryforwards	192	175
Deferred tax assets, net operating losses carryforwards - federal	0	1
Deferred tax assets, net operating losses carryforwards - state	0	0
Deferred tax assets, other	18	18
Subtotal deferred tax assets	210	194
Deferred tax assets, valuation allowances	0	(1)
Total deferred tax assets	210	193
Total deferred tax liabilities, net	753	702
ATC Holdings [Member]
Deferred tax liabilities, ATC Holdings	$ 123	$ 116

Income Taxes (Summary Of Tax Cr

Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Dec. 31, 2021USD ($)
Federal [Member]
Tax carryforwards, net operating losses	$ 186
Tax carryforwards, tax credits	560
Federal [Member] | IPL [Member]
Tax carryforwards, net operating losses	172
Tax carryforwards, tax credits	345
Federal [Member] | WPL [Member]
Tax carryforwards, net operating losses	1
Tax carryforwards, tax credits	192
State [Member]
Tax carryforwards, net operating losses	619
State [Member] | IPL [Member]
Tax carryforwards, net operating losses	28
State [Member] | WPL [Member]
Tax carryforwards, net operating losses	$ 2

Income Taxes (Schedule Of Uncer

Income Taxes (Schedule Of Uncertain Tax Positions) (Details)	12 Months Ended
	Dec. 31, 2021
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, 2021	Dec. 31, 2020
Benefit Plans [Line Items]
Total plan assets (less than 1%), percentage of common stock	1.00%	1.00%
Common stock percentage in assets held in 401(k) saving plans	9.00%	9.00%
Unrecognized compensation cost	$ 5
Percentage of base salary and short-term cash incentive compensation	100.00%
Carrying value of deferred compensation obligations	$ 22	$ 22
Performance Shares Equity Awards [Member]
Benefit Plans [Line Items]
Performance period	3 years
Performance Shares and Performance Units Liability Awards [Member]
Benefit Plans [Line Items]
Performance period	3 years
Instrument valuation based on shares of common stock, number of shares	1
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
Restricted Stock Units Liability 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	0.00%
Minimum [Member] | Performance Shares and Performance Units Liability Awards [Member]
Benefit Plans [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	0.00%
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	0.00%
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	200.00%
Maximum [Member] | Performance Shares and Performance Units Liability Awards [Member]
Benefit Plans [Line Items]
Actual number of shares paid out upon vesting, percentage of target shares	200.00%
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	200.00%
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)	9,000,000
Shares included in diluted earnings per share (in shares)	653,956

Benefit Plans (Assumptions Used

Benefit Plans (Assumptions Used To Measure Benefit Plans) (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	2.91%	2.57%	3.48%
Discount rate for net periodic cost	2.57%	3.48%	4.34%
Expected rate of return on plan assets	7.10%	7.10%	7.60%
Interest crediting rate for Alliant Energy Cash Balance Pension Plan	4.18%	4.76%	5.52%
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	2.94%	2.61%	3.51%
Discount rate for net periodic cost	2.61%	3.51%	4.35%
Expected rate of return on plan assets	7.10%	7.10%	7.60%
Rate of compensation increase	3.30%	3.65%	3.65%
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	2.94%	2.64%	3.50%
Discount rate for net periodic cost	2.64%	3.50%	4.35%
Expected rate of return on plan assets	7.10%	7.10%	7.60%
Rate of compensation increase	3.30%	3.65%	3.65%
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	2.81%	2.31%	3.40%
Discount rate for net periodic cost	2.31%	3.40%	4.24%
Expected rate of return on plan assets	4.80%	4.50%	5.44%
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	2.80%	2.28%	3.39%
Discount rate for net periodic cost	2.28%	3.39%	4.23%
Expected rate of return on plan assets	5.10%	4.50%	5.60%
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligations	2.79%	2.27%	3.39%
Discount rate for net periodic cost	2.27%	3.39%	4.23%
Expected rate of return on plan assets	4.02%	3.28%	3.81%
Minimum [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.30%	3.65%	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, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 11	$ 11	$ 10
Interest cost	34	43	50
Expected return on plan assets	(69)	(70)	(60)
Amortization of prior service cost (credit)	0	0	(1)
Amortization of actuarial loss	39	34	36
Settlement losses	0	12	0
Total	15	30	35
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	3	3
Interest cost	5	7	9
Expected return on plan assets	(5)	(5)	(5)
Amortization of prior service cost (credit)	0	0	0
Amortization of actuarial loss	5	3	3
Settlement losses	0	0	0
Total	9	8	10
IPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	7	6
Interest cost	16	20	23
Expected return on plan assets	(32)	(33)	(28)
Amortization of actuarial loss	17	15	15
Settlement losses	0	7	0
Total	8	16	16
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1
Interest cost	2	3	3
Expected return on plan assets	(3)	(4)	(4)
Amortization of actuarial loss	2	1	2
Settlement losses	0	0	0
Total	2	1	2
WPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4	3
Interest cost	15	19	21
Expected return on plan assets	(31)	(31)	(26)
Amortization of prior service cost (credit)	0	0	0
Amortization of actuarial loss	19	16	18
Total	7	8	16
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2	1
Interest cost	2	3	3
Expected return on plan assets	0	(1)	(1)
Amortization of prior service cost (credit)	0	(1)	0
Amortization of actuarial loss	2	2	2
Total	$ 5	$ 5	$ 5

Benefit Plans (Funded Status of

Benefit Plans (Funded Status of Benefits Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	$ 1,251	$ 1,351
Change in benefit obligation:
Net benefit obligation at January 1	1,351	1,280
Service cost	11	11	$ 10
Interest cost	34	43	50
Plan participants' contributions	0	0
Actuarial (gain) loss	(46)	132
Gross benefits paid	(99)	(115)
Net benefit obligation at December 31	1,251	1,351	1,280
Change in plan assets:
Fair value of plan assets at January 1	984	931
Actual return on plan assets	87	108
Employer contributions	39	60
Plan participants' contributions	0	0
Gross benefits paid	(99)	(115)
Fair value of plan assets at December 31	1,011	984	931
Under funded status at December 31	(240)	(367)
Fair value of plan assets	1,011	984	931
Pension Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	567	615
Change in benefit obligation:
Net benefit obligation at January 1	615	581
Service cost	7	7	6
Interest cost	16	20	23
Plan participants' contributions	0	0
Actuarial (gain) loss	(23)	60
Gross benefits paid	(48)	(53)
Net benefit obligation at December 31	567	615	581
Change in plan assets:
Fair value of plan assets at January 1	453	436
Actual return on plan assets	40	51
Employer contributions	17	19
Plan participants' contributions	0	0
Gross benefits paid	(48)	(53)
Fair value of plan assets at December 31	462	453	436
Under funded status at December 31	(105)	(162)
Fair value of plan assets	462	453	436
Pension Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	546	588
Change in benefit obligation:
Net benefit obligation at January 1	588	550
Service cost	4	4	3
Interest cost	15	19	21
Plan participants' contributions	0	0
Actuarial (gain) loss	(18)	55
Gross benefits paid	(43)	(40)
Net benefit obligation at December 31	546	588	550
Change in plan assets:
Fair value of plan assets at January 1	436	406
Actual return on plan assets	39	48
Employer contributions	18	22
Plan participants' contributions	0	0
Gross benefits paid	(43)	(40)
Fair value of plan assets at December 31	450	436	406
Under funded status at December 31	(96)	(152)
Fair value of plan assets	450	436	406
Other Postretirement Benefits Plans [Member]
Change in benefit obligation:
Net benefit obligation at January 1	227	214
Service cost	4	3	3
Interest cost	5	7	9
Plan participants' contributions	5	4
Actuarial (gain) loss	(12)	18
Gross benefits paid	(19)	(19)
Net benefit obligation at December 31	210	227	214
Change in plan assets:
Fair value of plan assets at January 1	108	105
Actual return on plan assets	4	11
Employer contributions	8	7
Plan participants' contributions	5	4
Gross benefits paid	(19)	(19)
Fair value of plan assets at December 31	106	108	105
Under funded status at December 31	(104)	(119)
Fair value of plan assets	106	108	105
Other Postretirement Benefits Plans [Member] | IPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	91	86
Service cost	1	1	1
Interest cost	2	3	3
Plan participants' contributions	2	1
Actuarial (gain) loss	(4)	8
Gross benefits paid	(8)	(8)
Net benefit obligation at December 31	84	91	86
Change in plan assets:
Fair value of plan assets at January 1	74	72
Actual return on plan assets	4	7
Employer contributions	2	2
Plan participants' contributions	2	1
Gross benefits paid	(8)	(8)
Fair value of plan assets at December 31	74	74	72
Under funded status at December 31	(10)	(17)
Fair value of plan assets	74	74	72
Other Postretirement Benefits Plans [Member] | WPL [Member]
Change in benefit obligation:
Net benefit obligation at January 1	89	85
Service cost	1	2	1
Interest cost	2	3	3
Plan participants' contributions	2	2
Actuarial (gain) loss	(5)	5
Gross benefits paid	(8)	(8)
Net benefit obligation at December 31	81	89	85
Change in plan assets:
Fair value of plan assets at January 1	18	17
Actual return on plan assets	0	2
Employer contributions	5	5
Plan participants' contributions	2	2
Gross benefits paid	(8)	(8)
Fair value of plan assets at December 31	17	18	17
Under funded status at December 31	(64)	(71)
Fair value of plan assets	$ 17	$ 18	$ 17

Benefit Plans (Amounts Recogniz

Benefit Plans (Amounts Recognized On The Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	$ (374)	$ (511)
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	(238)	(365)
Net amounts recognized at December 31	(240)	(367)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	429	533
Prior service credit	(4)	(5)
Net amount recognized at December 31	425	528
Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	13	8
Current liabilities	(8)	(8)
Pension and other benefit obligations	(109)	(119)
Net amounts recognized at December 31	(104)	(119)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	38	54
Prior service credit	(1)	(1)
Net amount recognized at December 31	37	53
IPL [Member]
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	(127)	(186)
IPL [Member] | Pension Plans, Defined Benefit [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	0	0
Current liabilities	0	(1)
Pension and other benefit obligations	(105)	(161)
Net amounts recognized at December 31	(105)	(162)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	180	228
Prior service credit	(1)	(1)
Net amount recognized at December 31	179	227
IPL [Member] | Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	10	4
Current liabilities	(2)	(2)
Pension and other benefit obligations	(18)	(19)
Net amounts recognized at December 31	(10)	(17)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	13	20
Prior service credit	0	0
Net amount recognized at December 31	13	20
WPL [Member]
Amounts recognized on the balance sheets consist of:
Pension and other benefit obligations	(159)	(222)
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	(96)	(152)
Net amounts recognized at December 31	(96)	(152)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	188	233
Prior service credit	(1)	(1)
Net amount recognized at December 31	187	232
WPL [Member] | Other Postretirement Benefits Plans [Member]
Amounts recognized on the balance sheets consist of:
Non-current assets	3	3
Current liabilities	(6)	(6)
Pension and other benefit obligations	(61)	(68)
Net amounts recognized at December 31	(64)	(71)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	18	25
Prior service credit	(1)	(1)
Net amount recognized at December 31	$ 17	$ 24

Benefit Plans (Accumulated Bene

Benefit Plans (Accumulated Benefit Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	$ 1,214	$ 1,305
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	1,214	1,305
Fair value of plan assets	1,011	984
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	1,251	1,351
Fair value of plan assets	1,011	984
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	210	227
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	210	227
Fair value of plan assets	106	108
IPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	546	589
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	546	589
Fair value of plan assets	462	453
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	567	615
Fair value of plan assets	462	453
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	84	91
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	84	91
Fair value of plan assets	74	74
WPL [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	532	573
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	532	573
Fair value of plan assets	450	436
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	546	588
Fair value of plan assets	450	436
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations	81	89
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	81	89
Fair value of plan assets	$ 17	$ 18

Benefit Plans (Regulatory Asset

Benefit Plans (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 35	$ 44
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets	$ 30	$ 34

Benefit Plans (Estimated Future

Benefit Plans (Estimated Future Funding) (Details) - Forecast [Member] $ in Millions	Dec. 31, 2022USD ($)
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2022	$ 2
Defined Benefit Pension Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2022	0
Defined Benefit Pension Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2022	0
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2022	8
Other Postretirement Benefits Plans [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2022	2
Other Postretirement Benefits Plans [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated funding for calendar year 2022	$ 6

Benefit Plans (Expected Benefit

Benefit Plans (Expected Benefit Payments) (Details) $ in Millions	Dec. 31, 2021USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	$ 103
Expected benefit payments, 2023	100
Expected benefit payments, 2024	99
Expected benefit payments, 2025	99
Expected benefit payments, 2026	99
Expected benefit payments, 2027 - 2031	458
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	85
Expected benefit payments, 2023	83
Expected benefit payments, 2024	82
Expected benefit payments, 2025	82
Expected benefit payments, 2026	83
Expected benefit payments, 2027 - 2031	387
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	18
Expected benefit payments, 2023	17
Expected benefit payments, 2024	17
Expected benefit payments, 2025	17
Expected benefit payments, 2026	16
Expected benefit payments, 2027 - 2031	71
IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	48
Expected benefit payments, 2023	47
Expected benefit payments, 2024	46
Expected benefit payments, 2025	46
Expected benefit payments, 2026	45
Expected benefit payments, 2027 - 2031	202
IPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	41
Expected benefit payments, 2023	40
Expected benefit payments, 2024	39
Expected benefit payments, 2025	39
Expected benefit payments, 2026	38
Expected benefit payments, 2027 - 2031	174
IPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	7
Expected benefit payments, 2023	7
Expected benefit payments, 2024	7
Expected benefit payments, 2025	7
Expected benefit payments, 2026	7
Expected benefit payments, 2027 - 2031	28
WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	44
Expected benefit payments, 2023	43
Expected benefit payments, 2024	42
Expected benefit payments, 2025	42
Expected benefit payments, 2026	40
Expected benefit payments, 2027 - 2031	190
WPL [Member] | Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	37
Expected benefit payments, 2023	36
Expected benefit payments, 2024	35
Expected benefit payments, 2025	35
Expected benefit payments, 2026	34
Expected benefit payments, 2027 - 2031	163
WPL [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments, 2022	7
Expected benefit payments, 2023	7
Expected benefit payments, 2024	7
Expected benefit payments, 2025	7
Expected benefit payments, 2026	6
Expected benefit payments, 2027 - 2031	$ 27

Benefit Plans (Allocation Of Pl

Benefit Plans (Allocation Of Plan Assets) (Details)	Dec. 31, 2021
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	3.00%
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	34.00%
Pension Plans, Defined Benefit [Member] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	21.00%
Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	9.00%
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	33.00%
Other Postretirement Benefits Plans [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	1.00%
Other Postretirement Benefits Plans [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	35.00%
Other Postretirement Benefits Plans [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual allocation, percentage	64.00%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	0.00%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	14.00%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	11.00%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	5.00%
Minimum [Member] | Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	25.00%
Minimum [Member] | Other Postretirement Benefits Plans [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	0.00%
Minimum [Member] | Other Postretirement Benefits Plans [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	0.00%
Minimum [Member] | Other Postretirement Benefits Plans [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	40.00%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	5.00%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	54.00%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	31.00%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Global asset securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	15.00%
Maximum [Member] | Pension Plans, Defined Benefit [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	45.00%
Maximum [Member] | Other Postretirement Benefits Plans [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	5.00%
Maximum [Member] | Other Postretirement Benefits Plans [Member] | Equity securites - U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	55.00%
Maximum [Member] | Other Postretirement Benefits Plans [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target range allocation, percentage	100.00%

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,011	$ 984	$ 931
Pension Plans, Defined Benefit [Member] | Assets measured at net asset value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	477	426
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	46
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	35	46
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	256	182
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	256	182
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] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	151
Pension Plans, Defined Benefit [Member] | Equity securities - international [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	151
Pension Plans, Defined Benefit [Member] | Equity securities - international [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plans, Defined Benefit [Member] | Equity securities - international [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	52	45
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52	45
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	191	134
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47	56
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	144	78
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]
Fair value of plan assets	534	558
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	355	434
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	179	124
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	462	453	436
Pension Plans, Defined Benefit [Member] | IPL [Member] | Assets measured at net asset value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	218	196
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	21
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	16	21
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	117	84
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	117	84
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] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	69
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securities - international [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	69
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securities - international [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 securities - international [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	24	21
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	24	21
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	87	62
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	21	26
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	66	36
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]
Fair value of plan assets	244	257
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	162	200
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82	57
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] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	450	436	406
Pension Plans, Defined Benefit [Member] | WPL [Member] | Assets measured at net asset value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	212	189
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	20
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	16	20
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	114	81
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	114	81
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] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	67
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securities - international [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	67
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securities - international [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 securities - international [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	23	20
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	23	20
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	85	59
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	21	25
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	64	34
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]
Fair value of plan assets	238	247
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	158	193
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	80	54
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
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	106	108	105
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70	78
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	3
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] | Assets measured at net asset value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29	27
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	2
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	5	2
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	11	4
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	11	4
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] | Equity securities - international [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	3
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securities - international [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	3
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securities - international [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 securities - international [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	0
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	0
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	60	72
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	58	71
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	2	1
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] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77	81
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	74	74	72
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50	51
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] | Assets measured at net asset value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23	22
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	8	0
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	8	0
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	42	51
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	42	51
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] | IPL [Member] | Subtotal [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51	52
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17	18	$ 17
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	18
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
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	1	0
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	1	0
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	0
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	0
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	15	18
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	15	18
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	$ (1)	$ (1)

Benefit Plans (Employees Partic

Benefit Plans (Employees Participate In Defined Contribution Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
401(k) costs	$ 26	$ 25	$ 25
IPL [Member]
401(k) costs	13	13	13
WPL [Member]
401(k) costs	$ 12	$ 12	$ 12

Benefit Plans (Recognized Compe

Benefit Plans (Recognized Compensation Expense And Income Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Compensation expense	$ 14	$ 16	$ 26
Income tax benefits	4	4	7
IPL [Member]
Compensation expense	8	9	15
Income tax benefits	2	2	4
WPL [Member]
Compensation expense	6	6	10
Income tax benefits	$ 2	$ 2	$ 3

Benefit Plans (Summary Of Perfo

Benefit Plans (Summary Of Performance Shares and Performance Units Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Performance Shares Equity Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	129,156	74,193	0
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 54.63	$ 47.44	$ 0
Granted (in shares/awards)	73,112	56,204	91,816
Granted, weighted average grant date fair value (in dollars per share)	$ 46.19	$ 64.04	$ 47.23
Forfeited (in shares/awards)	(5,839)	(1,241)	(17,623)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 51.07	$ 50.94	$ 46.35
Nonvested, December 31 (in shares/awards)	196,429	129,156	74,193
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 51.59	$ 54.63	$ 47.44
Performance Shares Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	68,307	131,872	203,188
Vested (in shares/awards)	(68,307)	(63,565)	(66,322)
Forfeited (in shares/awards)	0	0	(4,994)
Nonvested, December 31 (in shares/awards)	0	68,307	131,872
Performance Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	16,801	34,574	57,761
Vested (in shares/awards)	(16,801)	(16,661)	(20,131)
Forfeited (in shares/awards)	0	(1,112)	(3,056)
Nonvested, December 31 (in shares/awards)	0	16,801	34,574

Benefit Plans (Summary Of Per_2

Benefit Plans (Summary Of Performance Shares and Performance Units Vested Awards) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Performance Shares Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)	68,307	63,565	66,322
Performance Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)	16,801	16,661	20,131
2018 Grant [Member] | Performance Shares Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)	68,307
Vested percentage of the target	172.50%
Cash and stock payout value	$ 7
Cash payout value	$ 5
Common stock shares from vested performance shares (in shares)	13,644
2018 Grant [Member] | Performance Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)	16,801
Vested percentage of the target	172.50%
Cash and stock payout value	$ 2
Cash payout value	$ 2
2017 Grant [Member] | Performance Shares Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)		63,565
Vested percentage of the target		155.00%
Cash and stock payout value		$ 6
Cash payout value		$ 5
Common stock shares from vested performance shares (in shares)		9,543
2017 Grant [Member] | Performance Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)		16,661
Vested percentage of the target		155.00%
Cash and stock payout value		$ 2
Cash payout value		$ 2
2016 Grant [Member] | Performance Shares Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)			66,322
Vested percentage of the target			142.50%
Cash and stock payout value			$ 4
Cash payout value			$ 4
Common stock shares from vested performance shares (in shares)			6,447
2016 Grant [Member] | Performance Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares/awards)			20,131
Vested percentage of the target			142.50%
Cash and stock payout value			$ 1
Cash payout value			$ 1

Benefit Plans (Summary of Restr

Benefit Plans (Summary of Restricted Stock Units) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restricted Stock Units Equity Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	146,549	89,281	0
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 51.54	$ 46.04	$ 0
Granted (in shares/awards)	80,152	61,056	105,348
Granted, weighted average grant date fair value (in dollars per share)	$ 48.65	$ 59.42	$ 45.98
Forfeited (in shares/awards)	(8,882)	(3,788)	(16,067)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 49.84	$ 49.01	$ 45.63
Nonvested, December 31 (in shares/awards)	217,819	146,549	89,281
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 50.54	$ 51.54	$ 46.04
Restricted Stock Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	58,550	113,033	174,163
Vested (in shares/awards)	(58,550)	(54,483)	(56,849)
Forfeited (in shares/awards)	0	0	(4,281)
Nonvested, December 31 (in shares/awards)	0	58,550	113,033

Benefit Plans (Summary of Per_3

Benefit Plans (Summary of Performance Restricted Stock Units) (Details) - Performance Restricted Stock Units Equity Awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	197,463	206,065	203,188
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 47.31	$ 41.50	$ 37.23
Granted (in shares/awards)	73,112	56,204	91,816
Granted, weighted average grant date fair value (in dollars per share)	$ 48.66	$ 59.37	$ 46.10
Vested (in shares/awards)	(68,307)	(63,565)	(66,322)
Vested, weighted average grant date fair value (in dollars per share)	$ 38.60	$ 39.12	$ 33.93
Forfeited (in shares/awards)	(5,839)	(1,241)	(22,617)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 50.46	$ 49.25	$ 44
Nonvested, December 31 (in shares/awards)	196,429	197,463	206,065
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 50.74	$ 47.31	$ 41.50

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, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Carrying value of deferred compensation obligation	$ 12	$ 11
Fair market value of deferred compensation obligation	$ 24	$ 20

Asset Retirement Obligations (R

Asset Retirement Obligations (Reconciliation Of Changes In Asset Retirement Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	$ 251	$ 196
Revisions in estimated cash flows	50	13
Liabilities settled	(17)	(13)
Liabilities incurred	3	48
Accretion expense	7	7
Balance, December 31	294	251
IPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	177	134
Revisions in estimated cash flows	44	9
Liabilities settled	(13)	(9)
Liabilities incurred	0	38
Accretion expense	5	5
Balance, December 31	213	177
WPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	74	62
Revisions in estimated cash flows	6	4
Liabilities settled	(4)	(4)
Liabilities incurred	3	10
Accretion expense	2	2
Balance, December 31	$ 81	$ 74

Derivative Instruments (Notiona

Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) - Commodity [Member] gal in Thousands, T in Thousands, MWh in Thousands, Dekatherms in Thousands	12 Months Ended
	Dec. 31, 2021DekathermsMWhTgal
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	9,135
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	2,647
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs) | MWh	6,488
Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	191,670
Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	100,560
Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Dths) | Dekatherms	91,110
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	3,193
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	1,270
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Tons) | T	1,923
Diesel Fuel (gallons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	3,024
Diesel Fuel (gallons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	0
Diesel Fuel (gallons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in Gallons) | gal	3,024

Derivative Instruments (Fair Va

Derivative Instruments (Fair Value Of Financial Instruments) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 113	$ 24
Non-current derivative assets	63	10
Current derivative liabilities	8	9
Non-current derivative liabilities	1	16
IPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	48	20
Non-current derivative assets	36	9
Current derivative liabilities	4	3
Non-current derivative liabilities	0	9
WPL [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	65	4
Non-current derivative assets	27	1
Current derivative liabilities	4	6
Non-current derivative liabilities	$ 1	$ 7

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Assets:
Money market fund investments	$ 32	$ 44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	8,330	8,109
Commodity Contracts [Member]
Assets:
Derivatives	176	34
Liabilities and equity:
Derivatives	9	25
Level 1 [Member]
Assets:
Money market fund investments	32	44
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)	8,329	8,107
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	146	5
Liabilities and equity:
Derivatives	8	25
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	1	2
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	30	29
Liabilities and equity:
Derivatives	1	0
Carrying Amount [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	7,368	6,777
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	176	34
Liabilities and equity:
Derivatives	9	25
IPL [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	4,124	4,021
IPL [Member] | Commodity Contracts [Member]
Assets:
Derivatives	84	29
Liabilities and equity:
Derivatives	4	12
IPL [Member] | Level 1 [Member]
Assets:
Money market fund investments	32	44
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)	4,124	4,021
IPL [Member] | Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	65	3
Liabilities and equity:
Derivatives	3	12
IPL [Member] | Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	0	0
IPL [Member] | Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	19	26
Liabilities and equity:
Derivatives	1	0
IPL [Member] | Carrying Amount [Member]
Assets:
Money market fund investments	32	44
Deferred proceeds	214	188
Liabilities and equity:
Long-term debt (including current maturities)	3,643	3,345
IPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	84	29
Liabilities and equity:
Derivatives	4	12
WPL [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,862	2,690
WPL [Member] | Commodity Contracts [Member]
Assets:
Derivatives	92	5
Liabilities and equity:
Derivatives	5	13
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)	2,862	2,690
WPL [Member] | Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	81	2
Liabilities and equity:
Derivatives	5	13
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	11	3
Liabilities and equity:
Derivatives	0	0
WPL [Member] | Carrying Amount [Member]
Liabilities and equity:
Long-term debt (including current maturities)	2,429	2,130
WPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	92	5
Liabilities and equity:
Derivatives	$ 5	$ 13

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
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	$ 21
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	11
Purchases	21	14
Sales	(1)	(1)
Settlements	(26)	(16)
Ending balance, December 31	29	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	6	11
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	26	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	(3)	10
Purchases	16	11
Sales	(1)	(1)
Settlements	(20)	(12)
Ending balance, December 31	18	26
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	(3)	10
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	3	3
Total net gains (losses) included in changes in net assets (realized/unrealized)	9	1
Purchases	5	3
Settlements	(6)	(4)
Ending balance, December 31	11	3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	9	1
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance, January 1	188	188
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Purchases	0	0
Sales	0	0
Settlements	26	0
Ending balance, December 31	214	188
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	188	188
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Purchases	0	0
Sales	0	0
Settlements	26	0
Ending balance, December 31	214	188
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, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	$ 29	$ 29	$ 21
Excluding FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	9	18
FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	20	11
IPL [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	18	26	18
IPL [Member] | Excluding FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	8	17
IPL [Member] | FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	10	9
WPL [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	11	3	$ 3
WPL [Member] | Excluding FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	1	1
WPL [Member] | FTRs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net derivative assets	$ 10	$ 2

Commitments And Contingencies_2

Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
Workforce Subject to Collective Bargaining Arrangements [Member]
Long-term Purchase Commitment [Line Items]
Employees covered by collective bargaining agreement	54.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Long-term Purchase Commitment [Line Items]
Employees covered by collective bargaining agreement	26.00%
Whiting Petroleum Affiliate [Member]
Long-term Purchase Commitment [Line Items]
Partnership share, percent	6.00%
Obligations, maximum	$ 60
Credit loss liability	5
Capital Purchase Commitment [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	$ 178
IPL [Member] | Workforce Subject to Collective Bargaining Arrangements [Member]
Long-term Purchase Commitment [Line Items]
Employees covered by collective bargaining agreement	69.00%
WPL [Member] | Workforce Subject to Collective Bargaining Arrangements [Member]
Long-term Purchase Commitment [Line Items]
Employees covered by collective bargaining agreement	83.00%
WPL [Member] | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Long-term Purchase Commitment [Line Items]
Employees covered by collective bargaining agreement	83.00%
WPL [Member] | Capital Purchase Commitment [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	$ 177
Indemnification Agreement [Member]
Long-term Purchase Commitment [Line Items]
Obligations, maximum	67
Indemnification Agreement [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Obligations, maximum	$ 17

Commitments And Contingencies_3

Commitments And Contingencies (Other Purchase Commitments) (Details) $ in Millions	Dec. 31, 2021USD ($)
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	$ 452
Minimum future commitments, 2023	256
Minimum future commitments, 2024	177
Minimum future commitments, 2025	110
Minimum future commitments, 2026	90
Minimum future commitments, Thereafter	200
Minimum future commitments, Total	1,285
Individual commitments incurred	1
Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	307
Minimum future commitments, 2023	196
Minimum future commitments, 2024	144
Minimum future commitments, 2025	102
Minimum future commitments, 2026	88
Minimum future commitments, Thereafter	175
Minimum future commitments, Total	1,012
Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	63
Minimum future commitments, 2023	46
Minimum future commitments, 2024	25
Minimum future commitments, 2025	3
Minimum future commitments, 2026	0
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	137
Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	82
Minimum future commitments, 2023	14
Minimum future commitments, 2024	8
Minimum future commitments, 2025	5
Minimum future commitments, 2026	2
Minimum future commitments, Thereafter	25
Minimum future commitments, Total	136
IPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	214
Minimum future commitments, 2023	139
Minimum future commitments, 2024	103
Minimum future commitments, 2025	57
Minimum future commitments, 2026	44
Minimum future commitments, Thereafter	88
Minimum future commitments, Total	645
IPL [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	148
Minimum future commitments, 2023	108
Minimum future commitments, 2024	84
Minimum future commitments, 2025	52
Minimum future commitments, 2026	42
Minimum future commitments, Thereafter	65
Minimum future commitments, Total	499
IPL [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	32
Minimum future commitments, 2023	27
Minimum future commitments, 2024	17
Minimum future commitments, 2025	3
Minimum future commitments, 2026	0
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	79
IPL [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	34
Minimum future commitments, 2023	4
Minimum future commitments, 2024	2
Minimum future commitments, 2025	2
Minimum future commitments, 2026	2
Minimum future commitments, Thereafter	23
Minimum future commitments, Total	67
WPL [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	223
Minimum future commitments, 2023	108
Minimum future commitments, 2024	69
Minimum future commitments, 2025	51
Minimum future commitments, 2026	47
Minimum future commitments, Thereafter	110
Minimum future commitments, Total	608
WPL [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	159
Minimum future commitments, 2023	88
Minimum future commitments, 2024	60
Minimum future commitments, 2025	50
Minimum future commitments, 2026	46
Minimum future commitments, Thereafter	110
Minimum future commitments, Total	513
WPL [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	31
Minimum future commitments, 2023	19
Minimum future commitments, 2024	8
Minimum future commitments, 2025	0
Minimum future commitments, 2026	0
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	58
WPL [Member] | Other [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments, 2022	33
Minimum future commitments, 2023	1
Minimum future commitments, 2024	1
Minimum future commitments, 2025	1
Minimum future commitments, 2026	1
Minimum future commitments, Thereafter	0
Minimum future commitments, Total	$ 37

Commitments And Contingencies_4

Commitments And Contingencies (Schedule Of Environmental Liabilities) (Details) - Natural Gas Processing Plant [Member] $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
Current and non-current environmental liabilities	$ 11
IPL [Member]
Current and non-current environmental liabilities	8
Minimum [Member]
Range of estimated future costs	8
Minimum [Member] | IPL [Member]
Range of estimated future costs	6
Maximum [Member]
Range of estimated future costs	24
Maximum [Member] | IPL [Member]
Range of estimated future costs	$ 18

Segments Of Business (Narrative

Segments Of Business (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021segment
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, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 3,669	$ 3,416	$ 3,648
Depreciation and amortization	657	615	567
Operating income (loss)	795	740	778
Interest expense	277	275	273
Equity income from unconsolidated investments, net	(62)	(61)	(53)
Income tax expense (benefit)	(74)	(57)	69
Net income attributable to common shareowners	659	614	557
Total assets	18,553	17,710	16,701
Investments in equity method subsidiaries	508	476	458
Construction and acquisition expenditures	1,169	1,366	1,640
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	2,063	1,947	2,089
Operating income (loss)	460	410	403
Interest expense	139	139	127
Income tax expense (benefit)	(36)	(47)	24
Net income attributable to common shareowners	350	324	284
Total assets	9,996	9,849
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,523	1,395	1,476
Operating income (loss)	308	306	347
Interest expense	105	104	102
Income tax expense (benefit)	(51)	(19)	49
Total assets	7,518	6,912
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	3,081	2,920	3,064
Depreciation and amortization	591	556	513
Operating income (loss)	716	643	679
Equity income from unconsolidated investments, net	(2)	(2)	(1)
Total assets	14,924	14,358	13,659
Investments in equity method subsidiaries	17	11	9
Construction and acquisition expenditures	980	1,109	1,439
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,752	1,695	1,781
Depreciation and amortization	338	321	295
Operating income (loss)	420	358	360
Total assets	8,602	8,518	8,075
Construction and acquisition expenditures	342	626	964
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,329	1,225	1,283
Depreciation and amortization	253	235	218
Operating income (loss)	296	285	319
Total assets	6,322	5,840	5,584
Construction and acquisition expenditures	638	483	475
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	456	373	455
Depreciation and amortization	54	49	47
Operating income (loss)	63	74	70
Equity income from unconsolidated investments, net	0	0	0
Total assets	1,487	1,413	1,269
Investments in equity method subsidiaries	0	0	0
Construction and acquisition expenditures	90	182	100
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	265	208	264
Depreciation and amortization	31	30	29
Operating income (loss)	43	50	39
Total assets	819	766	734
Construction and acquisition expenditures	42	59	56
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	191	165	191
Depreciation and amortization	23	19	18
Operating income (loss)	20	24	31
Total assets	668	647	535
Construction and acquisition expenditures	48	123	44
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	49	49	46
Depreciation and amortization	6	5	3
Operating income (loss)	(11)	(1)	1
Equity income from unconsolidated investments, net	0	0	0
Total assets	1,103	990	856
Investments in equity method subsidiaries	0	0	0
Construction and acquisition expenditures	0	2	0
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	46	44	44
Depreciation and amortization	6	5	3
Operating income (loss)	(3)	2	4
Total assets	575	565	468
Construction and acquisition expenditures	0	2	0
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	3	5	2
Depreciation and amortization	0	0	0
Operating income (loss)	(8)	(3)	(3)
Total assets	528	425	388
Construction and acquisition expenditures	0	0	0
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	3,586	3,342	3,565
Depreciation and amortization	651	610	563
Operating income (loss)	768	716	750
Interest expense	244	243	229
Equity income from unconsolidated investments, net	(2)	(2)	(1)
Income tax expense (benefit)	(87)	(66)	73
Net income attributable to common shareowners	618	573	517
Total assets	17,514	16,761	15,784
Investments in equity method subsidiaries	17	11	9
Construction and acquisition expenditures	1,070	1,293	1,539
Utility Business [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	2,063	1,947	2,089
Depreciation and amortization	375	356	327
Operating income (loss)	460	410	403
Interest expense	139	139	127
Income tax expense (benefit)	(36)	(47)	24
Net income attributable to common shareowners	350	324	284
Total assets	9,996	9,849	9,277
Construction and acquisition expenditures	384	687	1,020
Utility Business [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,523	1,395	1,476
Depreciation and amortization	276	254	236
Operating income (loss)	308	306	347
Interest expense	105	104	102
Income tax expense (benefit)	(51)	(19)	49
Net income attributable to common shareowners	268	249	233
Total assets	7,518	6,912	6,507
Construction and acquisition expenditures	686	606	519
Non-Utility [Member]
Segment Reporting Information [Line Items]
Revenues	83	74	83
Depreciation and amortization	6	5	4
Operating income (loss)	27	24	28
Interest expense	33	32	44
Equity income from unconsolidated investments, net	(60)	(59)	(52)
Income tax expense (benefit)	13	9	(4)
Net income attributable to common shareowners	41	41	40
Total assets	1,039	949	917
Investments in equity method subsidiaries	491	465	449
Construction and acquisition expenditures	$ 99	$ 73	$ 101

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - WPL [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	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	$ 9	$ 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, 2021	Dec. 31, 2020	Dec. 31, 2019
Administrative and General Services Billings [Member] | IPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 180	$ 176	$ 185
Administrative and General Services Billings [Member] | WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	154	142	142
Transmission Sales Credited [Member] | IPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	22	35	68
Transmission Sales Credited [Member] | WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	23	3	7
Transmission Purchases Billed [Member] | IPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	441	329	331
Transmission Purchases Billed [Member] | WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 116	$ 108	$ 120

Related Parties (Net Intercompa

Related Parties (Net Intercompany Payables) (Details) - Corporate Services [Member] - Subsidiary of Common Parent [Member] - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
IPL [Member]
Related Party Transaction [Line Items]
Intercompany payables to Corporate Services	$ 110	$ 110
WPL [Member]
Related Party Transaction [Line Items]
Intercompany payables to Corporate Services	$ 83	$ 73

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, 2021	Dec. 31, 2020	Dec. 31, 2019
ATC Billings To WPL [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 122	$ 108	$ 109
WPL Billings To ATC [Member]
Related Party Transaction [Line Items]
Amounts billed between related parties	$ 18	$ 10	$ 13

Condensed Parent Company Fina_3

Condensed Parent Company Financial Statements (Condensed Statements Of Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses	$ 2,874	$ 2,676	$ 2,870
Operating income (loss)	795	740	778
Other (income) and deductions:
Equity earnings from consolidated subsidiaries	(62)	(61)	(53)
Interest expense	277	275	273
Total other (income) and deductions	195	173	142
Income before income taxes	600	567	636
Income tax benefit	(74)	(57)	69
Net income	674	624	567
Parent Company [Member]
Operating expenses	5	7	2
Operating income (loss)	(5)	(7)	(2)
Other (income) and deductions:
Equity earnings from consolidated subsidiaries	(664)	(625)	(562)
Interest expense	1	2	9
Other	1	4	7
Total other (income) and deductions	(662)	(619)	(546)
Income before income taxes	657	612	544
Income tax benefit	(5)	(4)	(15)
Net income	$ 662	$ 616	$ 559

Condensed Parent Company Fina_4

Condensed Parent Company Financial Statements (Condensed Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Other	$ 240	$ 123
Total current assets	1,069	887
Investments:
Other	179	154
Total investments	517	485
Other assets	1,980	2,002
Total assets	18,553	17,710	$ 16,701
Current liabilities:
Commercial paper	515	389
Other	226	207
Total current liabilities	2,054	1,297
Other liabilities	388	374
Common Equity:
Retained earnings	3,250	2,994
Shares in deferred compensation trust	(12)	(11)
Total common equity	5,990	5,688
Total liabilities and equity	18,553	17,710
Parent Company [Member]
Current assets:
Notes receivable from affiliated companies	16	32
Other	5	5
Total current assets	21	37
Investments:
Investments in consolidated subsidiaries	7,061	6,664
Other	2	2
Total investments	7,063	6,666
Other assets	96	88
Total assets	7,180	6,791
Current liabilities:
Commercial paper	279	132
Notes payable to affiliated companies	900	937
Other	4	29
Total current liabilities	1,183	1,098
Other liabilities	2	2
Common Equity:
Common stock and additional paid-in capital	2,752	2,706
Retained earnings	3,255	2,996
Shares in deferred compensation trust	(12)	(11)
Total common equity	5,995	5,691
Total liabilities and equity	$ 7,180	$ 6,791

Condensed Parent Company Fina_5

Condensed Parent Company Financial Statements (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net cash flows from operating activities	$ 582	$ 501	$ 660
Cash flows from (used for) investing activities:
Dividends from consolidated subsidiaries in excess of equity earnings	(61)	(43)	(60)
Net cash flows from (used for) investing activities	(728)	(951)	(1,287)
Cash flows used for financing activities:
Common stock dividends	(403)	(377)	(337)
Proceeds from issuance of common stock, net	28	247	390
Net change in commercial paper	126	52	(104)
Other	(13)	(27)	(24)
Net cash flows from (used for) financing activities	130	488	619
Net increase (decrease) in cash, cash equivalents and restricted cash	(16)	38	(8)
Cash, cash equivalents and restricted cash at beginning of period	56	18	26
Cash, cash equivalents and restricted cash at end of period	40	56	18
Supplemental cash flows information:
Interest	(272)	(274)	(268)
Income taxes, net	(3)	5	21
Parent Company [Member]
Net cash flows from operating activities	494	396	305
Cash flows from (used for) investing activities:
Capital contributions to consolidated subsidiaries	(295)	(429)	(250)
Net change in notes receivable from and payable to affiliates	(21)	201	8
Dividends from consolidated subsidiaries in excess of equity earnings	50	0	0
Net cash flows from (used for) investing activities	(266)	(228)	(242)
Cash flows used for financing activities:
Common stock dividends	(403)	(377)	(338)
Proceeds from issuance of common stock, net	28	247	390
Net change in commercial paper	147	(37)	(116)
Other	0	(1)	1
Net cash flows from (used for) financing activities	(228)	(168)	(63)
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	(1)	(2)	(9)
Income taxes, net	$ 4	$ 10	$ 14

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, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 18	$ 7	$ 10
Charged to Expense	12	25	17
Charged to Other Accounts	0	9	2
Deductions	19	23	22
Ending Balance	11	18	7
IPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1	1	3
Charged to Expense	6	18	16
Charged to Other Accounts	0	0	0
Deductions	6	18	18
Ending Balance	1	1	1
WPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	17	6	7
Charged to Expense	6	7	1
Charged to Other Accounts	0	9	2
Deductions	13	5	4
Ending Balance	$ 10	$ 17	$ 6