Acquisitions and Dispositions (Details) - USD ($)	3 Months Ended		9 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023	Dec. 31, 2023
Customers	$ 1,000,000,000			$ 1,029,900,000
Net Property, Plant and Equipment	77,796,000,000			76,693,400,000
Accounts Payable, Current	1,990,900,000			2,032,500,000
Proceeds from Sale of Equity Method Investments	114,000,000.0	$ 0
Generation And Marketing [Member] | New Mexico Renewable Development
Proceeds from Sale of Equity Method Investments	107,000,000
Generation And Marketing [Member] | Competitive Contracted Renewables
Proceeds from Sale of Productive Assets			$ 1,200,000,000
Gain (Loss) on Disposition of Business		112,000,000
gain (loss) on Disposition of Business net of Tax		88,000,000
Public Service Co Of Oklahoma [Member]
Customers	74,100,000			107,600,000
Net Property, Plant and Equipment	6,189,600,000			6,112,300,000
Accounts Payable, Current	138,500,000			159,300,000
Public Service Co Of Oklahoma [Member] | Vertically Integrated Utilities [Member] | Rock Falls Wind Facility
Payments to Acquire Property, Plant, and Equipment		$ 146,000,000
Southwestern Electric Power Co [Member]
Customers	32,700,000			39,000,000.0
Net Property, Plant and Equipment	8,666,700,000			8,558,400,000
Accounts Payable, Current	185,300,000			198,900,000
AEP Transmission Co [Member]
Customers	80,600,000			82,200,000
Net Property, Plant and Equipment	14,778,200,000			14,497,700,000
Accounts Payable, Current	$ 289,600,000			$ 274,700,000