Rate Matters and Regulation (Details)	6 Months Ended
	Jun. 30, 2020 USD ($)
Estimated Refund to SPP	$ 13,000,000.0
Public Utilities, Requested Rate Increase (Decrease), Amount	5,200,000
Investment in Grid Enhancement	800,000,000.0
Arkansas Environmental Refund	5,100,000
Impact to Company [Member]
Estimated Refund to SPP	5,000,000.0
Customer Impact [Member]
Estimated Refund to SPP	$ 8,000,000.0