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