XML 38 R18.htm IDEA: XBRL DOCUMENT v3.25.3

Segments Of Business

9 Months Ended

Sep. 30, 2025

Segment Reporting Information [Line Items]

Segments Of Business

SEGMENTS OF BUSINESS

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

			Utility
															Total												Alliant
															Reportable												Energy
Three Months Ended September 30, 2025			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$608						$516						$1,124						N/A						$1,124
Gas utility revenues			27						24						51						N/A						51
Other revenues			12						—						12						$23						35
Total revenues			647						540						1,187						23						1,210
Electric production fuel and purchased power expense			106						133						239						N/A						239
Electric transmission service expense			115						51						166						N/A						166
Cost of gas sold expense			7						5						12						N/A						12
Other operation and maintenance expense			108						84						192						12						204
Other segment items:
Depreciation and amortization expense			116						92						208						3						211
Interest expense			54						43						97						31						128
Equity income from unconsolidated investments, net			—						(1)						(1)						(17)						(18)
Income tax expense (benefit)			(21)						1						(20)						2						(18)
Other (a)			(3)						9						6						(1)						5
Net income (loss)			165						123						288						(7)						281
Total assets (as of September 30, 2025)			12,433						10,331						22,764						1,863						24,627
Investments in equity method subsidiaries (as of September 30, 2025)			5						19						24						644						668
Construction and acquisition expenditures			348						163						511						72						583

			Utility
															Total												Alliant
Three Months Ended September 30, 2024 (amounts may not foot due to rounding)															Reportable												Energy
			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$523						$476						$999						N/A						$999
Gas utility revenues			27						22						49						N/A						49
Other revenues			11						1						12						$21						33
Total revenues			561						499						1,060						21						1,081
Electric production fuel and purchased power expense			79						112						191						N/A						192
Electric transmission service expense			115						49						164						N/A						165
Cost of gas sold expense			8						5						13						N/A						13
Other operation and maintenance expense			96						72						168						6						174
Other segment items:
Depreciation and amortization expense			100						91						191						4						195
Interest expense			44						42						86						28						114
Equity income from unconsolidated investments, net			—						(1)						(1)						(13)						(14)
Income tax expense (benefit)			(68)						4						(64)						2						(62)
Other (a)			(3)						11						8						3						9
Net income (loss)			190						114						304						(9)						295
Total assets (as of September 30, 2024)			11,680						9,938						21,618						1,211						22,829
Investments in equity method subsidiaries (as of September 30, 2024)			5						17						22						594						616
Construction and acquisition expenditures			202						208						410						64						474

			Utility
															Total												Alliant
															Reportable												Energy
Nine Months Ended September 30, 2025			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$1,455						$1,373						$2,828						N/A						$2,828
Gas utility revenues			185						181						366						N/A						366
Other revenues			36						1						37						$67						104
Total revenues			1,676						1,555						3,231						67						3,298
Electric production fuel and purchased power expense			213						351						564						N/A						564
Electric transmission service expense			322						152						474						N/A						474
Cost of gas sold expense			89						91						180						N/A						180
Other operation and maintenance expense			275						222						497						33						530
Other segment items:
Depreciation and amortization expense			346						275						621						10						631
Interest expense			154						129						283						89						372
Equity income from unconsolidated investments, net			—						(1)						(1)						(40)						(41)
Income tax benefit			(98)						(9)						(107)						(2)						(109)
Other (a)			1						24						25						4						29
Net income (loss)			374						321						695						(27)						668
Construction and acquisition expenditures			976						511						1,487						161						1,648

			Utility
															Total												Alliant
Nine Months Ended September 30, 2024 (amounts may not foot due to rounding)															Reportable												Energy
			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$1,318						$1,261						$2,579						N/A						$2,579
Gas utility revenues			175						147						322						N/A						322
Other revenues			34						2						36						$68						104
Total revenues			1,527						1,410						2,937						68						3,005
Electric production fuel and purchased power expense			195						298						493						N/A						493
Electric transmission service expense			317						148						465						N/A						464
Cost of gas sold expense			85						67						152						N/A						152
Asset valuation charge for IPL’s Lansing Generating Station			60						—						60						N/A						60
Other operation and maintenance expense			281						200						481						29						510
Other segment items:
Depreciation and amortization expense			294						269						563						8						571
Interest expense			128						124						252						77						329
Equity income from unconsolidated investments, net			—						(2)						(2)						(42)						(44)
Income tax expense (benefit)			(112)						13						(99)						(5)						(104)
Other (a)			7						23						30						3						34
Net income (loss)			272						270						542						(2)						540
Construction and acquisition expenditures			702						578						1,280						154						1,434

(a)Other segment items for each reportable segment include allowance for funds used during construction, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

IPL [Member]

Segment Reporting Information [Line Items]

Segments Of Business

SEGMENTS OF BUSINESS

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

			Utility
															Total												Alliant
															Reportable												Energy
Three Months Ended September 30, 2025			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$608						$516						$1,124						N/A						$1,124
Gas utility revenues			27						24						51						N/A						51
Other revenues			12						—						12						$23						35
Total revenues			647						540						1,187						23						1,210
Electric production fuel and purchased power expense			106						133						239						N/A						239
Electric transmission service expense			115						51						166						N/A						166
Cost of gas sold expense			7						5						12						N/A						12
Other operation and maintenance expense			108						84						192						12						204
Other segment items:
Depreciation and amortization expense			116						92						208						3						211
Interest expense			54						43						97						31						128
Equity income from unconsolidated investments, net			—						(1)						(1)						(17)						(18)
Income tax expense (benefit)			(21)						1						(20)						2						(18)
Other (a)			(3)						9						6						(1)						5
Net income (loss)			165						123						288						(7)						281
Total assets (as of September 30, 2025)			12,433						10,331						22,764						1,863						24,627
Investments in equity method subsidiaries (as of September 30, 2025)			5						19						24						644						668
Construction and acquisition expenditures			348						163						511						72						583

			Utility
															Total												Alliant
Three Months Ended September 30, 2024 (amounts may not foot due to rounding)															Reportable												Energy
			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$523						$476						$999						N/A						$999
Gas utility revenues			27						22						49						N/A						49
Other revenues			11						1						12						$21						33
Total revenues			561						499						1,060						21						1,081
Electric production fuel and purchased power expense			79						112						191						N/A						192
Electric transmission service expense			115						49						164						N/A						165
Cost of gas sold expense			8						5						13						N/A						13
Other operation and maintenance expense			96						72						168						6						174
Other segment items:
Depreciation and amortization expense			100						91						191						4						195
Interest expense			44						42						86						28						114
Equity income from unconsolidated investments, net			—						(1)						(1)						(13)						(14)
Income tax expense (benefit)			(68)						4						(64)						2						(62)
Other (a)			(3)						11						8						3						9
Net income (loss)			190						114						304						(9)						295
Total assets (as of September 30, 2024)			11,680						9,938						21,618						1,211						22,829
Investments in equity method subsidiaries (as of September 30, 2024)			5						17						22						594						616
Construction and acquisition expenditures			202						208						410						64						474

			Utility
															Total												Alliant
															Reportable												Energy
Nine Months Ended September 30, 2025			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$1,455						$1,373						$2,828						N/A						$2,828
Gas utility revenues			185						181						366						N/A						366
Other revenues			36						1						37						$67						104
Total revenues			1,676						1,555						3,231						67						3,298
Electric production fuel and purchased power expense			213						351						564						N/A						564
Electric transmission service expense			322						152						474						N/A						474
Cost of gas sold expense			89						91						180						N/A						180
Other operation and maintenance expense			275						222						497						33						530
Other segment items:
Depreciation and amortization expense			346						275						621						10						631
Interest expense			154						129						283						89						372
Equity income from unconsolidated investments, net			—						(1)						(1)						(40)						(41)
Income tax benefit			(98)						(9)						(107)						(2)						(109)
Other (a)			1						24						25						4						29
Net income (loss)			374						321						695						(27)						668
Construction and acquisition expenditures			976						511						1,487						161						1,648

			Utility
															Total												Alliant
Nine Months Ended September 30, 2024 (amounts may not foot due to rounding)															Reportable												Energy
			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$1,318						$1,261						$2,579						N/A						$2,579
Gas utility revenues			175						147						322						N/A						322
Other revenues			34						2						36						$68						104
Total revenues			1,527						1,410						2,937						68						3,005
Electric production fuel and purchased power expense			195						298						493						N/A						493
Electric transmission service expense			317						148						465						N/A						464
Cost of gas sold expense			85						67						152						N/A						152
Asset valuation charge for IPL’s Lansing Generating Station			60						—						60						N/A						60
Other operation and maintenance expense			281						200						481						29						510
Other segment items:
Depreciation and amortization expense			294						269						563						8						571
Interest expense			128						124						252						77						329
Equity income from unconsolidated investments, net			—						(2)						(2)						(42)						(44)
Income tax expense (benefit)			(112)						13						(99)						(5)						(104)
Other (a)			7						23						30						3						34
Net income (loss)			272						270						542						(2)						540
Construction and acquisition expenditures			702						578						1,280						154						1,434

(a)Other segment items for each reportable segment include allowance for funds used during construction, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

WPL [Member]

Segment Reporting Information [Line Items]

Segments Of Business

SEGMENTS OF BUSINESS

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

			Utility
															Total												Alliant
															Reportable												Energy
Three Months Ended September 30, 2025			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$608						$516						$1,124						N/A						$1,124
Gas utility revenues			27						24						51						N/A						51
Other revenues			12						—						12						$23						35
Total revenues			647						540						1,187						23						1,210
Electric production fuel and purchased power expense			106						133						239						N/A						239
Electric transmission service expense			115						51						166						N/A						166
Cost of gas sold expense			7						5						12						N/A						12
Other operation and maintenance expense			108						84						192						12						204
Other segment items:
Depreciation and amortization expense			116						92						208						3						211
Interest expense			54						43						97						31						128
Equity income from unconsolidated investments, net			—						(1)						(1)						(17)						(18)
Income tax expense (benefit)			(21)						1						(20)						2						(18)
Other (a)			(3)						9						6						(1)						5
Net income (loss)			165						123						288						(7)						281
Total assets (as of September 30, 2025)			12,433						10,331						22,764						1,863						24,627
Investments in equity method subsidiaries (as of September 30, 2025)			5						19						24						644						668
Construction and acquisition expenditures			348						163						511						72						583

			Utility
															Total												Alliant
Three Months Ended September 30, 2024 (amounts may not foot due to rounding)															Reportable												Energy
			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$523						$476						$999						N/A						$999
Gas utility revenues			27						22						49						N/A						49
Other revenues			11						1						12						$21						33
Total revenues			561						499						1,060						21						1,081
Electric production fuel and purchased power expense			79						112						191						N/A						192
Electric transmission service expense			115						49						164						N/A						165
Cost of gas sold expense			8						5						13						N/A						13
Other operation and maintenance expense			96						72						168						6						174
Other segment items:
Depreciation and amortization expense			100						91						191						4						195
Interest expense			44						42						86						28						114
Equity income from unconsolidated investments, net			—						(1)						(1)						(13)						(14)
Income tax expense (benefit)			(68)						4						(64)						2						(62)
Other (a)			(3)						11						8						3						9
Net income (loss)			190						114						304						(9)						295
Total assets (as of September 30, 2024)			11,680						9,938						21,618						1,211						22,829
Investments in equity method subsidiaries (as of September 30, 2024)			5						17						22						594						616
Construction and acquisition expenditures			202						208						410						64						474

			Utility
															Total												Alliant
															Reportable												Energy
Nine Months Ended September 30, 2025			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$1,455						$1,373						$2,828						N/A						$2,828
Gas utility revenues			185						181						366						N/A						366
Other revenues			36						1						37						$67						104
Total revenues			1,676						1,555						3,231						67						3,298
Electric production fuel and purchased power expense			213						351						564						N/A						564
Electric transmission service expense			322						152						474						N/A						474
Cost of gas sold expense			89						91						180						N/A						180
Other operation and maintenance expense			275						222						497						33						530
Other segment items:
Depreciation and amortization expense			346						275						621						10						631
Interest expense			154						129						283						89						372
Equity income from unconsolidated investments, net			—						(1)						(1)						(40)						(41)
Income tax benefit			(98)						(9)						(107)						(2)						(109)
Other (a)			1						24						25						4						29
Net income (loss)			374						321						695						(27)						668
Construction and acquisition expenditures			976						511						1,487						161						1,648

			Utility
															Total												Alliant
Nine Months Ended September 30, 2024 (amounts may not foot due to rounding)															Reportable												Energy
			IPL						WPL						Segments						Other						Consolidated
Electric utility revenues			$1,318						$1,261						$2,579						N/A						$2,579
Gas utility revenues			175						147						322						N/A						322
Other revenues			34						2						36						$68						104
Total revenues			1,527						1,410						2,937						68						3,005
Electric production fuel and purchased power expense			195						298						493						N/A						493
Electric transmission service expense			317						148						465						N/A						464
Cost of gas sold expense			85						67						152						N/A						152
Asset valuation charge for IPL’s Lansing Generating Station			60						—						60						N/A						60
Other operation and maintenance expense			281						200						481						29						510
Other segment items:
Depreciation and amortization expense			294						269						563						8						571
Interest expense			128						124						252						77						329
Equity income from unconsolidated investments, net			—						(2)						(2)						(42)						(44)
Income tax expense (benefit)			(112)						13						(99)						(5)						(104)
Other (a)			7						23						30						3						34
Net income (loss)			272						270						542						(2)						540
Construction and acquisition expenditures			702						578						1,280						154						1,434

(a)Other segment items for each reportable segment include allowance for funds used during construction, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

X

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-15

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 11: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 16: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-34

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26C

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26B

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/280/tableOfContent

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

+ Details

Name:	us-gaap_SegmentReportingDisclosureTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: