Rate Matters and Regulation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Estimated Refund to SPP	$ 13.0
Investment in Grid Enhancement	800.0
Plant Investments For Customers	28.0
Other Commitment	1,000.0
Minimum [Member]
Lost Revenue on Plant Investments for Customers	14.5
Loss Contingency, Range of Possible Loss, Maximum	800.0
Maximum [Member]
Lost Revenue on Plant Investments for Customers	21.7
Loss Contingency, Range of Possible Loss, Maximum	1,000.0
In Favor Cooperatives [Member]
Plant Investments For Customers	11.7
In Favor Cooperatives [Member] | Minimum [Member]
Lost Revenue on Plant Investments for Customers	1.4
In Favor Cooperatives [Member] | Maximum [Member]
Lost Revenue on Plant Investments for Customers	2.3
Impact to Company [Member]
Estimated Refund to SPP	5.0
Customer Impact [Member]
Estimated Refund to SPP	$ 8.0
Oklahoma Corporation Commission [Member]
OG&E's Jurisdictional Revenues	86.00%
Arkansas Public Service Commission [Member]
OG&E's Jurisdictional Revenues	8.00%
Federal Energy Regulatory Commission [Member]
OG&E's Jurisdictional Revenues	6.00%
Arkansas Environmental [Member]
Customer Refund Amount	$ 5.3
Grid Enhancement
OCC Revenue Requirement	7.0
ARKANSAS
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 6.7	$ 5.2