Condensed Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Revenues:
Electric utility	$ 853	$ 791
Gas utility	240	205
Other utility	13	13
Non-utility	22	22
Total revenues	1,128	1,031
Operating expenses:
Electric production fuel and purchased power	175	163
Electric transmission service	158	152
Cost of gas sold	137	114
Other operation and maintenance	160	160
Depreciation and amortization	211	189
Taxes other than income taxes	30	31
Total operating expenses	871	809
Operating income	257	222
Other (income) and deductions:
Interest expense	119	107
Equity income from unconsolidated investments, net	(13)	(15)
Allowance for funds used during construction	(18)	(19)
Other	3	1
Total other (income) and deductions	91	74
Income before income taxes	166	148
Income tax expense (benefit)	(47)	(10)
Net income attributable to common shareowners	$ 213	$ 158
Weighted average number of common shares outstanding:
Basic (in shares)	256,800	256,200
Diluted (in shares)	257,200	256,500
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 0.83	$ 0.62
Diluted (in dollars per share)	$ 0.83	$ 0.62
IPL [Member]
Revenues:
Electric utility	$ 430	$ 392
Gas utility	118	108
Other utility	12	13
Total revenues	560	513
Operating expenses:
Electric production fuel and purchased power	67	67
Electric transmission service	108	103
Cost of gas sold	65	60
Other operation and maintenance	82	86
Depreciation and amortization	115	96
Taxes other than income taxes	15	16
Total operating expenses	452	428
Operating income	108	85
Other (income) and deductions:
Interest expense	47	42
Allowance for funds used during construction	(9)	(10)
Total other (income) and deductions	38	32
Income before income taxes	70	53
Income tax expense (benefit)	(40)	(10)
Net income attributable to common shareowners	110	63
WPL [Member]
Revenues:
Electric utility	423	399
Gas utility	122	97
Other utility	1	0
Total revenues	546	496
Operating expenses:
Electric production fuel and purchased power	108	96
Electric transmission service	50	49
Cost of gas sold	72	53
Other operation and maintenance	67	63
Depreciation and amortization	93	90
Taxes other than income taxes	14	14
Total operating expenses	404	365
Operating income	142	131
Other (income) and deductions:
Interest expense	43	41
Allowance for funds used during construction	(9)	(9)
Other	3	1
Total other (income) and deductions	37	33
Income before income taxes	105	98
Income tax expense (benefit)	(5)	6
Net income attributable to common shareowners	$ 110	$ 92