EFFECTS OF REGULATION - Regulatory Assets - SWEPCo (Details) - USD ($) $ in Millions	Dec. 31, 2025	Nov. 30, 2025	Dec. 31, 2024	Feb. 20, 2021
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 426		$ 446
Total Noncurrent Regulatory Assets	4,804		5,129
Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1,307		1,311
Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	3,497		3,818
Earns/earning a return | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 84		84
Remaining Recovery Period	1 year
Earns/earning a return | Under-recovered Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 140		246
Remaining Recovery Period	1 year
Earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 435		395
Earns/earning a return | Pending final regulatory approval | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	0		33
Earns/earning a return | Pending final regulatory approval | Welsh Plant, Units 1 and 3 Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	220		169
Earns/earning a return | Pending final regulatory approval | Pirkey Plant Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	93		121
Earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	43		51
Earns/earning a return | Pending final regulatory approval | Other Regulatory Assets Pending Final Regulatory Approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	23		21
Earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1,341		1,711
Earns/earning a return | Approved for recovery | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 22		63
Remaining Recovery Period	2 years
Earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 100		107
Remaining Recovery Period	6 years
Earns/earning a return | Approved for recovery | Fuel Mine Closure Costs - Texas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 65		71
Remaining Recovery Period	10 years
Earns/earning a return | Approved for recovery | Pirkey Plant Accelerated Depreciation - Arkansas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 41		0
Remaining Recovery Period	10 years
Earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 199		204
Does not earns/earning a return | Under-recovered Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 202		116
Remaining Recovery Period	1 year
Does not earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 872		916
Does not earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	191		301
Does not earns/earning a return | Pending final regulatory approval | Other Regulatory Assets Pending Final Regulatory Approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	163		87
Does not earns/earning a return | Pending final regulatory approval | NOLC Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	89		93
Does not earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	2,156		2,107
Does not earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 158		67
Remaining Recovery Period	6 years
Does not earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 222		229
Does not earns/earning a return | Approved for recovery | Pension and OPEB Funded Status
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 796		974
Remaining Recovery Period	12 years
Does not earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Texas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 45		45
Remaining Recovery Period	21 years
SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 115		107
Total Noncurrent Regulatory Assets	903		921
SOUTHWESTERN ELECTRIC POWER COMPANY | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets				$ 106
SOUTHWESTERN ELECTRIC POWER COMPANY | Unrecovered Winter Storm Fuel Costs | Arkansas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets				$ 22
Remaining Recovery Period				6 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Unrecovered Winter Storm Fuel Costs | Louisiana
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets				$ 41
Remaining Recovery Period		5 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Unrecovered Winter Storm Fuel Costs | TEXAS
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets				$ 43
Remaining Recovery Period				5 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	445		454
SOUTHWESTERN ELECTRIC POWER COMPANY | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	458		467
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 84		84
Remaining Recovery Period	1 year
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Under-recovered Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 31		23
Remaining Recovery Period	1 year
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 316		346
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	0		33
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Welsh Plant, Units 1 and 3 Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	220		169
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Pirkey Plant Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	93		121
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Dolet Hills Power Station Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	0		12
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	2		10
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Other Regulatory Assets Pending Final Regulatory Approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1		1
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	301		293
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 22		63
Remaining Recovery Period	2 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Pirkey Plant Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 72		66
Remaining Recovery Period	7 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Dolet Hills Power Station Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 13		0
Remaining Recovery Period	21 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 10		0
Remaining Recovery Period	3 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Fuel Mine Closure Costs - Texas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 65		71
Remaining Recovery Period	10 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Pirkey Plant Accelerated Depreciation - Arkansas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 41		0
Remaining Recovery Period	10 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant - Arkansas, Louisiana
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 31		40
Remaining Recovery Period	17 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Dolet Hills Power Station - Louisiana
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 15		19
Remaining Recovery Period	7 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Dolet Hills Power Station Fuel Costs - Louisiana
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 14		22
Remaining Recovery Period	2 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 18		12
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	129		108
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	43		40
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Pending final regulatory approval | Other Regulatory Assets Pending Final Regulatory Approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	20		18
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Pending final regulatory approval | NOLC Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	66		50
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	157		174
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant - Arkansas, Louisiana
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 10		13
Remaining Recovery Period	2 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 25		23
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Pension and OPEB Funded Status
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 77		93
Remaining Recovery Period	12 years
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Texas
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 45		$ 45
Remaining Recovery Period	21 years