FAIR VALUE MEASUREMENTS - Significant Unobservable Inputs (Details) - USD ($)	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	$ 555,900,000	$ 499,500,000
Fair value, liabilities	330,900,000	324,400,000
APCo
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	31,500,000	37,100,000
Fair value, liabilities	2,900,000	2,200,000
I&M
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	3,900,000	18,400,000
Fair value, liabilities	3,200,000	700,000
OPCo
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	0	0
Fair value, liabilities	51,200,000	47,500,000
PSO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	34,200,000	22,000,000.0
Fair value, liabilities	1,100,000	5,800,000
SWEPCo
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	17,900,000	18,100,000
Fair value, liabilities	400,000	2,300,000
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	253,100,000	313,500,000
Fair value, liabilities	130,300,000	147,900,000
Energy Contracts | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	203,300,000	221,200,000
Fair value, liabilities	124,200,000	144,600,000
Energy Contracts | Level 3 | OPCo
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	0	0
Fair value, liabilities	$ 51,200,000	$ 47,500,000
Energy Contracts | Level 3 | Low | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(17.47)	2.75
Input/Range, liability	(17.47)	2.75
Energy Contracts | Level 3 | Low | OPCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	14.76	14.53
Input/Range, liability	14.76	14.53
Energy Contracts | Level 3 | High | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	165.62	149.30
Input/Range, liability	165.62	149.30
Energy Contracts | Level 3 | High | OPCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	74.75	72.40
Input/Range, liability	74.75	72.40
Energy Contracts | Level 3 | Weighted Average | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	47.92	49.34
Input/Range, liability	47.92	49.34
Energy Contracts | Level 3 | Weighted Average | OPCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	39.26	42.44
Input/Range, liability	39.26	42.44
FTRs | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	$ 49,800,000	$ 92,300,000
Fair value, liabilities	6,100,000	3,300,000
FTRs | Level 3 | APCo
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	11,500,000	35,200,000
Fair value, liabilities	3,500,000	0
FTRs | Level 3 | I&M
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	4,100,000	6,900,000
Fair value, liabilities	200,000	500,000
FTRs | Level 3 | PSO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	15,600,000	20,800,000
Fair value, liabilities	200,000	800,000
FTRs | Level 3 | SWEPCo
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, assets	13,400,000	18,100,000
Fair value, liabilities	$ 300,000	$ 600,000
FTRs | Level 3 | Low | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(33.92)	(29.48)
Input/Range, liability	(33.92)	(29.48)
FTRs | Level 3 | Low | APCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(1.63)	(0.25)
Input/Range, liability	(1.63)	(0.25)
FTRs | Level 3 | Low | I&M | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(2.80)	(4.07)
Input/Range, liability	(2.80)	(4.07)
FTRs | Level 3 | Low | PSO | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(33.92)	(29.48)
Input/Range, liability	(33.92)	(29.48)
FTRs | Level 3 | Low | SWEPCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(33.92)	(29.48)
Input/Range, liability	(33.92)	(29.48)
FTRs | Level 3 | High | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	14.27	19.70
Input/Range, liability	14.27	19.70
FTRs | Level 3 | High | APCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	6.48	9.32
Input/Range, liability	6.48	9.32
FTRs | Level 3 | High | I&M | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	7.28	9.32
Input/Range, liability	7.28	9.32
FTRs | Level 3 | High | PSO | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	8.98	10.54
Input/Range, liability	8.98	10.54
FTRs | Level 3 | High | SWEPCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	8.98	10.54
Input/Range, liability	8.98	10.54
FTRs | Level 3 | Weighted Average | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(0.58)	0.24
Input/Range, liability	(0.58)	0.24
FTRs | Level 3 | Weighted Average | APCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	0.88	1.56
Input/Range, liability	0.88	1.56
FTRs | Level 3 | Weighted Average | I&M | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	2.05	1.34
Input/Range, liability	2.05	1.34
FTRs | Level 3 | Weighted Average | PSO | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(6.60)	(3.88)
Input/Range, liability	(6.60)	(3.88)
FTRs | Level 3 | Weighted Average | SWEPCo | Forward Market Price
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Input/Range, asset	(6.60)	(3.88)
Input/Range, liability	(6.60)	(3.88)