FAIR VALUE MEASUREMENTS - Summary of Nuclear Trust Investments (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2026	Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 5,241	$ 4,916
Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	2,939	2,649
Gross Unrealized Losses	(15)	(9)
Other-Than-Temporary Impairments	(23)	(21)
INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	5,241	4,916
INDIANA MICHIGAN POWER COMPANY \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	2,939	2,649
Gross Unrealized Losses	(15)	(9)
Other-Than-Temporary Impairments	(23)	(21)
Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	22	29
Cash and Cash Equivalents \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Other-Than-Temporary Impairments	0	0
Cash and Cash Equivalents \| INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	22	29
Cash and Cash Equivalents \| INDIANA MICHIGAN POWER COMPANY \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Other-Than-Temporary Impairments	0	0
United States Government
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,322	1,351
United States Government \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	8	22
Gross Unrealized Losses	(3)	(1)
Other-Than-Temporary Impairments	(17)	(15)
United States Government \| INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,322	1,351
United States Government \| INDIANA MICHIGAN POWER COMPANY \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	8	22
Gross Unrealized Losses	(3)	(1)
Other-Than-Temporary Impairments	(17)	(15)
Corporate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	412	376
Corporate Debt \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	3	6
Gross Unrealized Losses	(10)	(7)
Other-Than-Temporary Impairments	(6)	(6)
Corporate Debt \| INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	412	376
Corporate Debt \| INDIANA MICHIGAN POWER COMPANY \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	3	6
Gross Unrealized Losses	(10)	(7)
Other-Than-Temporary Impairments	(6)	(6)
Subtotal Fixed Income Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,734	1,727
Subtotal Fixed Income Securities \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	11	28
Gross Unrealized Losses	(13)	(8)
Other-Than-Temporary Impairments	(23)	(21)
Subtotal Fixed Income Securities \| INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,734	1,727
Subtotal Fixed Income Securities \| INDIANA MICHIGAN POWER COMPANY \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	11	28
Gross Unrealized Losses	(13)	(8)
Other-Than-Temporary Impairments	(23)	(21)
Equity Securities - Domestic
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	3,485	3,160
Equity Securities - Domestic \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	2,928	2,621
Gross Unrealized Losses	(2)	(1)
Other-Than-Temporary Impairments	0	0
Equity Securities - Domestic \| INDIANA MICHIGAN POWER COMPANY
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	3,485	3,160
Equity Securities - Domestic \| INDIANA MICHIGAN POWER COMPANY \| Spent Nuclear Fuel and Decommissioning Trusts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Unrealized Gains	2,928	2,621
Gross Unrealized Losses	(2)	(1)
Other-Than-Temporary Impairments	$ 0	$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-10

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-12

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-13

+ Details

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

- Details

Name:	aeptexas_TrustAssetsAxis=aeptexas_SpentNuclearFuelandDecommissioningTrustsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FixedIncomeFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=aeptexas_DomesticEquitySecutiriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: