Condensed Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Revenues:
Electric utility	$ 1,124	$ 999	$ 2,828	$ 2,579
Gas utility	51	49	366	322
Other utility	12	12	37	36
Non-utility	23	21	67	68
Total revenues	1,210	1,081	3,298	3,005
Operating expenses:
Electric production fuel and purchased power	239	192	564	493
Electric transmission service	166	165	474	464
Cost of gas sold	12	13	180	152
Asset valuation charge for IPL's Lansing Generating Station	0	0	0	60
Other operation and maintenance	204	174	530	510
Depreciation and amortization	211	195	631	571
Taxes other than income taxes	29	29	91	90
Total operating expenses	861	768	2,470	2,340
Operating income	349	313	828	665
Other (income) and deductions:
Interest expense	128	114	372	329
Equity income from unconsolidated investments, net	(18)	(14)	(41)	(44)
Allowance for funds used during construction	(24)	(20)	(65)	(58)
Other	0	0	3	2
Total other (income) and deductions	86	80	269	229
Income before income taxes	263	233	559	436
Income tax expense (benefit)	(18)	(62)	(109)	(104)
Net income attributable to common shareowners	$ 281	$ 295	$ 668	$ 540
Weighted average number of common shares outstanding:
Basic (in shares)	257,000	256,600	256,900	256,400
Diluted (in shares)	257,800	256,900	257,500	256,700
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 1.09	$ 1.15	$ 2.60	$ 2.11
Diluted (in dollars per share)	$ 1.09	$ 1.15	$ 2.59	$ 2.10
IPL [Member]
Revenues:
Electric utility	$ 608	$ 523	$ 1,455	$ 1,318
Gas utility	27	27	185	175
Other utility	12	11	36	34
Total revenues	647	561	1,676	1,527
Operating expenses:
Electric production fuel and purchased power	106	79	213	195
Electric transmission service	115	115	322	317
Cost of gas sold	7	8	89	85
Asset valuation charge for IPL's Lansing Generating Station	0	0	0	60
Other operation and maintenance	108	96	275	281
Depreciation and amortization	116	100	346	294
Taxes other than income taxes	15	14	44	45
Total operating expenses	467	412	1,289	1,277
Operating income	180	149	387	250
Other (income) and deductions:
Interest expense	54	44	154	128
Allowance for funds used during construction	(15)	(13)	(37)	(34)
Other	(3)	(4)	(6)	(4)
Total other (income) and deductions	36	27	111	90
Income before income taxes	144	122	276	160
Income tax expense (benefit)	(21)	(68)	(98)	(112)
Net income attributable to common shareowners	165	190	374	272
WPL [Member]
Revenues:
Electric utility	516	476	1,373	1,261
Gas utility	24	22	181	147
Other utility	0	1	1	2
Total revenues	540	499	1,555	1,410
Operating expenses:
Electric production fuel and purchased power	133	112	351	298
Electric transmission service	51	49	152	148
Cost of gas sold	5	5	91	67
Other operation and maintenance	84	72	222	200
Depreciation and amortization	92	91	275	269
Taxes other than income taxes	13	14	42	41
Total operating expenses	378	343	1,133	1,023
Operating income	162	156	422	387
Other (income) and deductions:
Interest expense	43	42	129	124
Allowance for funds used during construction	(9)	(7)	(28)	(24)
Other	4	3	9	4
Total other (income) and deductions	38	38	110	104
Income before income taxes	124	118	312	283
Income tax expense (benefit)	1	4	(9)	13
Net income attributable to common shareowners	$ 123	$ 114	$ 321	$ 270