Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Electric utility	$ 3,081	$ 2,920	$ 3,064
Gas utility	456	373	455
Other utility	49	49	46
Non-utility	83	74	83
Total revenues	3,669	3,416	3,648
Operating expenses:
Electric production fuel and purchased power	642	652	777
Electric transmission service	537	449	481
Cost of gas sold	258	182	222
Other operation and maintenance	676	670	712
Depreciation and amortization	657	615	567
Taxes other than income taxes	104	108	111
Total operating expenses	2,874	2,676	2,870
Operating income (loss)	795	740	778
Other (income) and deductions:
Interest expense	277	275	273
Equity income from unconsolidated investments, net	(62)	(61)	(53)
Allowance for funds used during construction	(25)	(55)	(93)
Other	5	14	15
Total other (income) and deductions	195	173	142
Income before income taxes	600	567	636
Income tax expense (benefit)	(74)	(57)	69
Net income	674	624	567
Preferred dividend requirements of Interstate Power and Light Company	15	10	10
Net income attributable to common shareowners	$ 659	$ 614	$ 557
Weighted average number of common shares outstanding:
Basic (in shares)	250.2	248.4	238.5
Diluted (in shares)	250.7	248.7	239.0
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic (in dollars per share)	$ 2.63	$ 2.47	$ 2.34
Diluted (in dollars per share)	$ 2.63	$ 2.47	$ 2.33
IPL [Member]
Revenues:
Electric utility	$ 1,752	$ 1,695	$ 1,781
Gas utility	265	208	264
Other utility	46	44	44
Total revenues	2,063	1,947	2,089
Operating expenses:
Electric production fuel and purchased power	295	352	435
Electric transmission service	367	298	340
Cost of gas sold	149	99	120
Other operation and maintenance	362	375	404
Depreciation and amortization	375	356	327
Taxes other than income taxes	55	57	60
Total operating expenses	1,603	1,537	1,686
Operating income (loss)	460	410	403
Other (income) and deductions:
Interest expense	139	139	127
Allowance for funds used during construction	(9)	(24)	(50)
Other	1	8	8
Total other (income) and deductions	131	123	85
Income before income taxes	329	287	318
Income tax expense (benefit)	(36)	(47)	24
Net income	365	334	294
Preferred dividend requirements of Interstate Power and Light Company	15	10	10
Net income attributable to common shareowners	350	324	284
WPL [Member]
Revenues:
Electric utility	1,329	1,225	1,283
Gas utility	191	165	191
Other utility	3	5	2
Total revenues	1,523	1,395	1,476
Operating expenses:
Electric production fuel and purchased power	347	300	342
Electric transmission service	170	151	141
Cost of gas sold	109	83	102
Other operation and maintenance	268	254	261
Depreciation and amortization	276	254	236
Taxes other than income taxes	45	47	47
Total operating expenses	1,215	1,089	1,129
Operating income (loss)	308	306	347
Other (income) and deductions:
Interest expense	105	104	102
Allowance for funds used during construction	(16)	(31)	(43)
Other	2	3	6
Total other (income) and deductions	91	76	65
Income before income taxes	217	230	282
Income tax expense (benefit)	(51)	(19)	49
Net income	$ 268	$ 249	$ 233