Condensed Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenues:
Electric utility	$ 851	$ 789	$ 1,703	$ 1,580
Gas utility	76	69	316	273
Other utility	11	10	25	24
Non-utility	23	26	44	48
Total revenues	961	894	2,088	1,925
Operating expenses:
Electric production fuel and purchased power	150	138	325	301
Electric transmission service	151	147	308	300
Cost of gas sold	30	25	167	139
Asset valuation charge for IPL's Lansing Generating Station	0	60	0	60
Other operation and maintenance	168	177	327	336
Depreciation and amortization	208	188	420	376
Taxes other than income taxes	31	29	62	61
Total operating expenses	738	764	1,609	1,573
Operating income	223	130	479	352
Other (income) and deductions:
Interest expense	124	108	243	215
Equity income from unconsolidated investments, net	(10)	(15)	(23)	(31)
Allowance for funds used during construction	(23)	(19)	(41)	(38)
Other	1	2	4	4
Total other (income) and deductions	92	76	183	150
Income before income taxes	131	54	296	202
Income tax expense (benefit)	(43)	(33)	(91)	(43)
Net income attributable to common shareowners	$ 174	$ 87	$ 387	$ 245
Weighted average number of common shares outstanding:
Basic (in shares)	256,900	256,400	256,800	256,300
Diluted (in shares)	257,300	256,700	257,300	256,600
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 0.68	$ 0.34	$ 1.51	$ 0.96
Diluted (in dollars per share)	$ 0.68	$ 0.34	$ 1.50	$ 0.95
IPL [Member]
Revenues:
Electric utility	$ 418	$ 404	$ 848	$ 795
Gas utility	40	40	158	148
Other utility	11	9	24	23
Total revenues	469	453	1,030	966
Operating expenses:
Electric production fuel and purchased power	40	48	107	116
Electric transmission service	100	99	207	202
Cost of gas sold	17	17	81	77
Asset valuation charge for IPL's Lansing Generating Station	0	60	0	60
Other operation and maintenance	84	102	169	187
Depreciation and amortization	115	97	230	193
Taxes other than income taxes	15	14	29	30
Total operating expenses	371	437	823	865
Operating income	98	16	207	101
Other (income) and deductions:
Interest expense	52	42	99	84
Allowance for funds used during construction	(13)	(11)	(22)	(21)
Other	(2)	0	(2)	0
Total other (income) and deductions	37	31	75	63
Income before income taxes	61	(15)	132	38
Income tax expense (benefit)	(37)	(33)	(77)	(43)
Net income attributable to common shareowners	98	18	209	81
WPL [Member]
Revenues:
Electric utility	433	385	855	785
Gas utility	36	29	158	125
Other utility	0	1	1	1
Total revenues	469	415	1,014	911
Operating expenses:
Electric production fuel and purchased power	110	90	218	186
Electric transmission service	51	49	101	98
Cost of gas sold	13	8	86	62
Other operation and maintenance	72	67	137	128
Depreciation and amortization	90	87	183	178
Taxes other than income taxes	15	14	29	28
Total operating expenses	351	315	754	680
Operating income	118	100	260	231
Other (income) and deductions:
Interest expense	43	41	86	82
Allowance for funds used during construction	(10)	(8)	(19)	(17)
Other	3	0	5	2
Total other (income) and deductions	36	33	72	67
Income before income taxes	82	67	188	164
Income tax expense (benefit)	(5)	3	(10)	8
Net income attributable to common shareowners	$ 87	$ 64	$ 198	$ 156