Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Electric utility	$ 3,345	$ 3,421	$ 3,081
Gas utility	540	642	456
Other utility	52	49	49
Non-utility	90	93	83
Total revenues	4,027	4,205	3,669
Operating expenses:
Electric production fuel and purchased power	736	830	642
Electric transmission service	583	573	537
Cost of gas sold	299	389	258
Other operation and maintenance	675	704	676
Depreciation and amortization	676	671	657
Taxes other than income taxes	115	110	104
Total operating expenses	3,084	3,277	2,874
Operating income (loss)	943	928	795
Other (income) and deductions:
Interest expense	394	325	277
Equity income from unconsolidated investments, net	(61)	(51)	(62)
Allowance for funds used during construction	(100)	(60)	(25)
Other	3	6	5
Total other (income) and deductions	236	220	195
Income before income taxes	707	708	600
Income tax expense (benefit)	4	22	(74)
Net income	703	686	674
Preferred dividend requirements of Interstate Power and Light Company	0	0	15
Net income attributable to common shareowners	$ 703	$ 686	$ 659
Weighted average number of common shares outstanding:
Basic (in shares)	253.0	250.9	250.2
Diluted (in shares)	253.3	251.2	250.7
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 2.78	$ 2.73	$ 2.63
Diluted (in dollars per share)	$ 2.78	$ 2.73	$ 2.63
IPL [Member]
Revenues:
Electric utility	$ 1,761	$ 1,859	$ 1,752
Gas utility	300	351	265
Other utility	49	46	46
Total revenues	2,110	2,256	2,063
Operating expenses:
Electric production fuel and purchased power	282	383	295
Electric transmission service	420	407	367
Cost of gas sold	166	206	149
Other operation and maintenance	353	369	362
Depreciation and amortization	388	381	375
Taxes other than income taxes	57	57	55
Total operating expenses	1,666	1,803	1,603
Operating income (loss)	444	453	460
Other (income) and deductions:
Interest expense	155	148	139
Allowance for funds used during construction	(21)	(11)	(9)
Other	2	6	1
Total other (income) and deductions	136	143	131
Income before income taxes	308	310	329
Income tax expense (benefit)	(58)	(50)	(36)
Net income	366	360	365
Preferred dividend requirements of Interstate Power and Light Company	0	0	15
Net income attributable to common shareowners	366	360	350
WPL [Member]
Revenues:
Electric utility	1,584	1,562	1,329
Gas utility	240	291	191
Other utility	3	3	3
Total revenues	1,827	1,856	1,523
Operating expenses:
Electric production fuel and purchased power	455	447	347
Electric transmission service	163	166	170
Cost of gas sold	134	183	109
Other operation and maintenance	271	278	268
Depreciation and amortization	280	283	276
Taxes other than income taxes	52	47	45
Total operating expenses	1,355	1,404	1,215
Operating income (loss)	472	452	308
Other (income) and deductions:
Interest expense	149	121	105
Allowance for funds used during construction	(79)	(49)	(16)
Other	(3)	(1)	2
Total other (income) and deductions	67	71	91
Income before income taxes	405	381	217
Income tax expense (benefit)	60	66	(51)
Net income	$ 345	$ 315	$ 268