EFFECTS OF REGULATION - Regulatory Asset - PSO (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 | 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 | 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 | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 106.7	170.9
Remaining Recovery Period	7 years
Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 661.2	664.2
Remaining Recovery Period	22 years
Earns/earning a return | Approved for recovery | Environmental Control Projects
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 29.1	31.4
Remaining Recovery Period	16 years
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 | 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 | 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 | 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]
Total Noncurrent Regulatory Assets	$ 66.5	38.5
Remaining Recovery Period	7 years
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]
Total Noncurrent Regulatory Assets	$ 974.2	1,054.1
Remaining Recovery Period	12 years
Does not earns/earning a return | Approved for recovery | Unrealized Loss on Forward Commitments
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 53.3	131.4
Remaining Recovery Period	8 years
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
PUBLIC SERVICE COMPANY OF OKLAHOMA | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	497.5	434.0
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Under-recovered Fuel Costs
Regulatory Asset [Line Items]
Total Current Regulatory Assets	$ 64.7	118.3
Remaining Recovery Period	1 year
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 425.4	325.3
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Approved for recovery | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 106.7	26.2
Remaining Recovery Period	7 years
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Approved for recovery | Plant Retirement Costs - Unrecovered Plant
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 274.0	254.1
Remaining Recovery Period	22 years
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Approved for recovery | Environmental Control Projects
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 21.2	22.5
Remaining Recovery Period	16 years
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Approved for recovery | Meter Replacement Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 10.1	14.1
Remaining Recovery Period	3 years
PUBLIC SERVICE COMPANY OF OKLAHOMA | Earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 13.4	8.4
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Pending final regulatory approval
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	30.3	88.7
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Pending final regulatory approval | NOCL - Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	16.4	0.0
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Pending final regulatory approval | Storm-Related Costs
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	4.9	88.5
PUBLIC SERVICE COMPANY OF OKLAHOMA | 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	9.0	0.2
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Approved for recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	72.1	108.7
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Approved for recovery | Other Regulatory Assets Approved for Recovery
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	10.6	16.2
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Approved for recovery | Pension and OPEB Funded Status
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 57.6	62.6
Remaining Recovery Period	12 years
PUBLIC SERVICE COMPANY OF OKLAHOMA | Does not earns/earning a return | Approved for recovery | Unrealized Loss on Forward Commitments
Regulatory Asset [Line Items]
Total Noncurrent Regulatory Assets	$ 3.9	$ 29.9
Remaining Recovery Period	2 years