Leases - Schedule of Financial Statement Information of Lease Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Leased Assets [Line Items]
Operating lease cost		$ 6.4	$ 5.9	$ 6.3
Operating cash flows for operating leases		5.2	5.3	6.3
Right-of-use assets obtained in exchange for new operating lease liabilities		0.0	1.5	0.0
Right-of-use assets at period end	[1]	$ 25.9	$ 30.2
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]		Property, Plant and Equipment, Net	Property, Plant and Equipment, Net
Operating lease liabilities at period end	[2]	$ 30.5	$ 34.8
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]		Liabilities, Other than Long-Term Debt, Noncurrent	Liabilities, Other than Long-Term Debt, Noncurrent
Operating lease weighted-average remaining lease term (in years)		11 years 4 months 24 days	11 years 7 months 6 days
Operating lease weighted-average discount rate		4.00%	4.00%
OG&E [Member]
Operating Leased Assets [Line Items]
Operating lease cost		$ 6.4	$ 5.9	5.7
Operating cash flows for operating leases		5.2	5.3	5.7
Right-of-use assets obtained in exchange for new operating lease liabilities		0.0	1.5	$ 0.0
Right-of-use assets at period end	[1]	$ 25.9	$ 30.2
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]		Property, Plant and Equipment, Net	Property, Plant and Equipment, Net
Operating lease liabilities at period end	[2]	$ 30.5	$ 34.8
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]		Liabilities, Other than Long-Term Debt, Noncurrent	Liabilities, Other than Long-Term Debt, Noncurrent
Operating lease weighted-average remaining lease term (in years)		11 years 4 months 24 days	11 years 7 months 6 days
Operating lease weighted-average discount rate		4.00%	4.00%

[1] Included in Property, Plant and Equipment in the Registrants' balance sheets.

[2] Included in Other Deferred Credits and Other Liabilities in the Registrants' balance sheets.