Fair Value Measurements - Summary of Financial Instrument Measured at Fair Value On A Recurring Basis and Carrying Amount and Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
OGE Energy Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	$ 347.8	$ 347.6
Long-Term Debt, Fair Value	358.1	362.5
OGE Energy Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	59.9	59.9
Long-Term Debt, Fair Value	60.0	60.0
OG&E Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	4,847.4	4,847.2
Long-Term Debt, Fair Value	4,589.3	4,644.7
OG&E Industrial Authority Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	103.0	103.0
Long-Term Debt, Fair Value	103.0	103.0
OG&E Tinker Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	11.5	11.5
Long-Term Debt, Fair Value	$ 9.0	$ 9.1