Rate Matters and Regulation Rate Matters and Regulation (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
Estimated Refund to SPP	$ 13.0
Plan Investments for Customers	28.0
Requested Recovery of Capital Investment	1,200.0
Securitization Authorization Requested	760.0
Maximum [Member]
Lost Revenue on Plant Investments for Customers	42.7
Minimum [Member]
Lost Revenue on Plant Investments for Customers	31.4
In Favor Cooperatives
Plan Investments for Customers	11.7
In Favor Cooperatives | Maximum [Member]
Lost Revenues on Plant Investments for Customers	5.1
In Favor Cooperatives | Minimum [Member]
Lost Revenues on Plant Investments for Customers	3.2
OKLAHOMA
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 163.5
Public Utilities, Requested Return on Equity, Percentage	10.20%
Common Equity Percentage which ROE is based	53.37%
ARKANSAS
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 4.2
Impact to Company [Member]
Estimated Refund to SPP	5.0
Customer Impact [Member]
Estimated Refund to SPP	$ 8.0