Condensed Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenues:
Electric utility	$ 791	$ 768
Gas utility	205	276
Other utility	13	11
Non-utility	22	22
Total revenues	1,031	1,077
Operating expenses:
Electric production fuel and purchased power	163	157
Electric transmission service	152	146
Cost of gas sold	114	181
Other operation and maintenance	160	174
Depreciation and amortization	189	166
Taxes other than income taxes	31	31
Total operating expenses	809	855
Operating income	222	222
Other (income) and deductions:
Interest expense	107	94
Equity income from unconsolidated investments, net	(15)	(17)
Allowance for funds used during construction	(19)	(19)
Other	1	3
Total other (income) and deductions	74	61
Income before income taxes	148	161
Income tax expense (benefit)	(10)	(2)
Net income	158	163
Net income attributable to common shareowners	$ 158	$ 163
Weighted average number of common shares outstanding:
Basic (in shares)	256,200	251,200
Diluted (in shares)	256,500	251,400
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 0.62	$ 0.65
Diluted (in dollars per share)	$ 0.62	$ 0.65
IPL [Member]
Revenues:
Electric utility	$ 392	$ 388
Gas utility	108	150
Other utility	13	11
Total revenues	513	549
Operating expenses:
Electric production fuel and purchased power	67	47
Electric transmission service	103	104
Cost of gas sold	60	95
Other operation and maintenance	86	95
Depreciation and amortization	96	96
Taxes other than income taxes	16	16
Total operating expenses	428	453
Operating income	85	96
Other (income) and deductions:
Interest expense	42	37
Allowance for funds used during construction	(10)	(3)
Other	0	1
Total other (income) and deductions	32	35
Income before income taxes	53	61
Income tax expense (benefit)	(10)	(11)
Net income	63	72
WPL [Member]
Revenues:
Electric utility	399	380
Gas utility	97	126
Total revenues	496	506
Operating expenses:
Electric production fuel and purchased power	96	109
Electric transmission service	49	42
Cost of gas sold	53	86
Other operation and maintenance	63	66
Depreciation and amortization	90	68
Taxes other than income taxes	14	14
Total operating expenses	365	385
Operating income	131	121
Other (income) and deductions:
Interest expense	41	36
Allowance for funds used during construction	(9)	(16)
Other	1	1
Total other (income) and deductions	33	21
Income before income taxes	98	100
Income tax expense (benefit)	6	12
Net income	$ 92	$ 88