EFFECTS OF REGULATION - Regulatory Asset - SWEPCo (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 445.9	$ 514.0
Total Noncurrent Regulatory Assets	5,129.2	5,092.4
Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1,310.8	837.3
Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	3,818.4	4,255.1
Earns/earning a return | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 84.2	93.9
Remaining Recovery Period	1 year
Earns/earning a return | Under-recovered Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 245.7	357.4
Remaining Recovery Period	1 year
Earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 395.1	349.9
Earns/earning a return | Pending final regulatory approval | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	33.5	60.1
Earns/earning a return | Pending final regulatory approval | Welsh Plant, Units 1 and 3 Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	168.6	125.6
Earns/earning a return | Pending final regulatory approval | Pirkey Plant Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	121.3	114.4
Earns/earning a return | Pending final regulatory approval | Other Regulatory Assets Pending Final Regulatory Approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	20.7	49.8
Earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	51.0	0.0
Earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 1,711.5	1,946.9
Earns/earning a return | Approved for recovery | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 62.8	99.3
Earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	7 years
Total Noncurrent Regulatory Assets	$ 106.7	170.9
Earns/earning a return | Approved for recovery | Fuel Mine Closure Costs - Texas
Regulatory Asset [Line Items]
Remaining Recovery Period	11 years
Total Noncurrent Regulatory Assets	$ 70.6	74.3
Earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	159.9	124.9
Does not earns/earning a return | Under-recovered Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 116.0	62.7
Remaining Recovery Period	1 year
Does not earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 915.7	487.4
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	86.3	52.6
Does not earns/earning a return | Pending final regulatory approval | NOLC - Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	92.8	0.0
Does not earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	300.8	408.9
Does not earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 2,106.9	2,308.2
Does not earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	7 years
Total Noncurrent Regulatory Assets	$ 66.5	38.5
Does not earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 240.1	269.1
Does not earns/earning a return | Approved for recovery | Pension and OPEB Funded Status
Regulatory Asset [Line Items]
Remaining Recovery Period	12 years
Total Noncurrent Regulatory Assets	$ 974.2	1,054.1
Does not earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Texas
Regulatory Asset [Line Items]
Remaining Recovery Period	22 years
Total Noncurrent Regulatory Assets	$ 44.5	48.7
Does not earns/earning a return | Approved for recovery | Unrealized Loss on Forward Commitments
Regulatory Asset [Line Items]
Remaining Recovery Period	8 years
Total Noncurrent Regulatory Assets	$ 53.3	131.4
SOUTHWESTERN ELECTRIC POWER COMPANY
Regulatory Asset [Line Items]
Total Current Regulatory Assets	106.6	170.8
Total Noncurrent Regulatory Assets	921.3	1,131.8
SOUTHWESTERN ELECTRIC POWER COMPANY | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	454.2	407.8
SOUTHWESTERN ELECTRIC POWER COMPANY | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	467.1	724.0
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 84.2	93.9
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	$ 22.4	76.9
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	$ 346.0	338.1
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	33.5	60.1
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	168.6	125.6
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Pending final regulatory approval | Pirkey Plant Accelerated Depreciation
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	121.3	114.4
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	11.8	12.0
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	10.8	26.0
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 293.3	483.1
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Unrecovered Winter Storm Fuel Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 62.8	99.3
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Pirkey Plant Accelerated Depreciation
Regulatory Asset [Line Items]
Remaining Recovery Period	8 years
Total Noncurrent Regulatory Assets	$ 66.4	65.8
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 0.0	144.7
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Fuel Mine Closure Costs - Texas
Regulatory Asset [Line Items]
Remaining Recovery Period	11 years
Total Noncurrent Regulatory Assets	$ 70.6	74.3
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Arkansas
Regulatory Asset [Line Items]
Remaining Recovery Period	18 years
Total Noncurrent Regulatory Assets	$ 40.2	44.4
SOUTHWESTERN ELECTRIC POWER COMPANY | Earns/earning a return | Approved for recovery | Dolet Hills Power Station Fuel Costs - Louisiana
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 21.7	0.0
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]
Remaining Recovery Period	8 years
Total Noncurrent Regulatory Assets	$ 19.0	40.8
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	12.6	13.8
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	108.2	69.7
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	18.7	13.7
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Pending final regulatory approval | NOLC - Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	49.6	0.0
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	39.9	56.0
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 173.8	240.9
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Arkansas
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 12.8	17.3
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	$ 22.1	30.1
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Pension and OPEB Funded Status
Regulatory Asset [Line Items]
Remaining Recovery Period	12 years
Total Noncurrent Regulatory Assets	$ 93.2	109.2
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant, Texas
Regulatory Asset [Line Items]
Remaining Recovery Period	22 years
Total Noncurrent Regulatory Assets	$ 44.5	48.7
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | Unrealized Loss on Forward Commitments
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 1.2	15.4
SOUTHWESTERN ELECTRIC POWER COMPANY | Does not earns/earning a return | Approved for recovery | North Central Wind Rider
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 0.0	$ 20.2