EFFECTS OF REGULATION - Regulatory Asset (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
Regulatory Liabilities and Deferred Investment Tax Credits	8,344.0	8,182.4
PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Current Regulatory Assets	64.7	118.3
Total Noncurrent Regulatory Assets	527.8	522.7
Regulatory Liabilities and Deferred Investment Tax Credits	689.7	765.6
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
Approved for recovery | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	497.5	434.0
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 | Under-recovered Fuel Costs | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 64.7	118.3
Remaining Recovery Period	1 year
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 | 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 | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	51.0	0.0
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 | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	1,711.5	1,946.9
Earns/earning a return | Approved for recovery | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 425.4	325.3
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 | Storm-Related Costs | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Remaining Recovery Period	7 years
Total Noncurrent Regulatory Assets	$ 106.7	26.2
Earns/earning a return | Approved for recovery | Plant Retirement Costs - Asset Retirement Obligation Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	16 years
Total Noncurrent Regulatory Assets	$ 111.0	110.8
Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant
Regulatory Asset [Line Items]
Remaining Recovery Period	22 years
Total Noncurrent Regulatory Assets	$ 661.2	664.2
Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Remaining Recovery Period	22 years
Total Noncurrent Regulatory Assets	$ 274.0	254.1
Earns/earning a return | Approved for recovery | Long-term Under-recovered Fuel Costs - West Virginia
Regulatory Asset [Line Items]
Remaining Recovery Period	10 years
Total Noncurrent Regulatory Assets	$ 283.8	291.5
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 | Pirkey Plant Accelerated Depreciation - Louisiana
Regulatory Asset [Line Items]
Remaining Recovery Period	8 years
Total Noncurrent Regulatory Assets	$ 66.4	65.8
Earns/earning a return | Approved for recovery | Kentucky Deferred Purchased Power Expenses
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 45.0	43.5
Earns/earning a return | Approved for recovery | Rockport Plant Dry Sorbent Injection System and Selective Catalytic Reduction
Regulatory Asset [Line Items]
Remaining Recovery Period	4 years
Total Noncurrent Regulatory Assets	$ 37.3	46.9
Earns/earning a return | Approved for recovery | Texas Mobile Temporary Emergency Electric Energy Facilities Rider
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 32.6	33.4
Earns/earning a return | Approved for recovery | Environmental Control Projects
Regulatory Asset [Line Items]
Remaining Recovery Period	16 years
Total Noncurrent Regulatory Assets	$ 29.1	31.4
Earns/earning a return | Approved for recovery | Environmental Control Projects | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Remaining Recovery Period	16 years
Total Noncurrent Regulatory Assets	$ 21.2	22.5
Earns/earning a return | Approved for recovery | Ohio Basic Transmission Cost Rider
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 26.1	42.2
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
Earns/earning a return | Approved for recovery | Long-term Under-recovered Fuel Costs - Virginia
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	0.0	107.0
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
Earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	13.4	8.4
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 | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	30.3	88.7
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 | Pending final regulatory approval | Storm-Related Costs | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	4.9	88.5
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 | Other Regulatory Assets Pending Final Regulatory Approval | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	9.0	0.2
Does not earns/earning a return | Pending final regulatory approval | Plant Retirement Costs - Asset Retirement Obligation Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	357.4	25.9
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 | 2024-2025 Virginia Under-Earnings
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	78.4	0.0
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 | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 72.1	108.7
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 | Plant Retirement Costs - Asset Retirement Obligation Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	18 years
Total Noncurrent Regulatory Assets	$ 360.1	330.2
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 | Other Regulatory Assets Approved for Recovery | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 10.6	16.2
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 | Pension and OPEB Funded Status | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Remaining Recovery Period	12 years
Total Noncurrent Regulatory Assets	$ 57.6	62.6
Does not earns/earning a return | Approved for recovery | Unamortized Loss on Reacquired Debt
Regulatory Asset [Line Items]
Remaining Recovery Period	24 years
Total Noncurrent Regulatory Assets	$ 90.9	97.2
Does not earns/earning a return | Approved for recovery | Fuel and Purchased Power Adjustment Rider
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 57.4	68.3
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
Does not earns/earning a return | Approved for recovery | Unrealized Loss on Forward Commitments | PUBLIC SERVICE COMPANY OF OKLAHOMA
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 3.9	29.9
Does not earns/earning a return | Approved for recovery | OVEC Purchased Power
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 52.0	50.1
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 | Cook Plant Nuclear Refueling Outage Levelization
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 43.0	55.7
Does not earns/earning a return | Approved for recovery | Smart Grid Costs
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 33.8	26.3
Does not earns/earning a return | Approved for recovery | Postemployment Benefits
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 27.9	30.6
Does not earns/earning a return | Approved for recovery | Ohio Enhanced Service Reliability Plan
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 26.2	35.3
Does not earns/earning a return | Approved for recovery | 2020-2022 Virginia Triennial Under Earnings
Regulatory Asset [Line Items]
Remaining Recovery Period	3 years
Total Noncurrent Regulatory Assets	$ 26.0	37.4
Does not earns/earning a return | Approved for recovery | Ohio Distribution Investment Rider
Regulatory Asset [Line Items]
Remaining Recovery Period	2 years
Total Noncurrent Regulatory Assets	$ 11.0	$ 35.3