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Retirement Plans and Postretirement Benefit Plans (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Pension Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Service cost $ 1.4 $ 1.4
Interest cost $ 3.8 $ 4.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Expected return on plan assets $ (3.7) $ (4.0)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Amortization of net (gain) loss $ 1.7 $ 2.2
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Amortization of unrecognized prior service cost [1] $ 0.0 $ 0.0
Settlement cost 0.0 18.2
Net periodic benefit cost 3.2 21.8
Capitalized portion of net periodic pension benefit cost 0.0 0.6
Other Pension Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Service cost 0.2 0.3
Interest cost $ 0.1 $ 0.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Expected return on plan assets $ 0.0 $ 0.0
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Amortization of net (gain) loss $ 0.0 $ 0.0
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Amortization of unrecognized prior service cost [1] $ 0.1 $ 0.1
Settlement cost 0.0 0.0
Net periodic benefit cost 0.4 0.4
Postretirement Benefit Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Service cost 0.0 0.0
Interest cost 1.3 1.3
Expected return on plan assets (0.4) (0.4)
Amortization of net (gain) loss (0.1) (0.1)
Total net periodic benefit cost 0.8 0.8
Plus: Amount allocated from OGE Energy 0.0 0.0
Net periodic benefit cost 0.8 0.8
Capitalized portion of net periodic pension benefit cost 0.0 0.0
OG&E [Member] | Pension Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Service cost 1.4 1.1
Interest cost $ 3.3 $ 3.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Expected return on plan assets $ (3.2) $ (3.2)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Amortization of net (gain) loss $ 1.6 $ 1.9
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Settlement cost $ 0.0 $ 17.2
Total net periodic benefit cost 3.1 20.1
Plus: Amount allocated from OGE Energy 0.0 1.6
Net periodic benefit cost 3.1 21.7
Capitalized portion of net periodic pension benefit cost 0.6 0.5
OG&E [Member] | Other Pension Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Service cost 0.0 0.0
Interest cost $ 0.0 $ 0.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Expected return on plan assets $ 0.0 $ 0.0
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Amortization of net (gain) loss $ 0.0 $ 0.0
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Pension and Other Postretirement Benefits Cost (Reversal of Cost) Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Settlement cost $ 0.0 $ 0.0
Total net periodic benefit cost 0.0 0.0
Plus: Amount allocated from OGE Energy 0.4 0.4
Net periodic benefit cost 0.4 0.4
OG&E [Member] | Postretirement Benefit Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Service cost 0.0 0.0
Interest cost 1.0 1.0
Expected return on plan assets (0.4) (0.4)
Amortization of net (gain) loss 0.0 0.0
Total net periodic benefit cost 0.6 0.6
Plus: Amount allocated from OGE Energy 0.1 0.1
Net periodic benefit cost 0.7 0.7
Capitalized portion of net periodic pension benefit cost 0.0 0.0
Oklahoma Jurisdiction | Pension Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Settlement cost [2] 0.0 16.7
Change in postretirement expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) [2] 3.3 20.2
Arkansas Jurisdiction | Pension Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Settlement cost [2] 0.0 1.5
OKLAHOMA | Postretirement Benefit Plan [Member]    
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]    
Change in postretirement expense to maintain allowed recoverable amount in Oklahoma jurisdiction (A) [3] $ 1.1 $ 1.1
[1] Unamortized prior service cost is amortized on a straight-line basis over the average remaining service period to the first eligibility age of participants who are expected to receive a benefit and are active at the date of the plan amendment.
[2] Included in the pension regulatory asset in each jurisdiction, as indicated in the regulatory assets and liabilities table in Note 1.
[3] Included in the pension regulatory asset, as indicated in the regulatory assets and liabilities table in Note 1.