Rate Matters and Regulation (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 5.2
Customer Refund Liability, Current		4.8	$ 0.3
Regulatory Assets, Current		48.7	18.5
Public Utilities, Amount Requested for Acquisition		53.5
Estimated Refund to SPP		13.0
Investment in Grid Enhancement		800.0
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%
OKLAHOMA
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 77.6
ARKANSAS
Public Utilities, Approved Rate Increase (Decrease), Amount		(3.3)
Oklahoma demand program rider under recovery [Member]
Regulatory Assets, Current	[1]	$ 0.0	$ 6.4
FERC [Member]
Recommended Common Equity Percentage		7.85%
Public Utilities, Approved Return on Equity, Percentage		10.60%

[1] Included in Other Current Assets in the Consolidated Balance Sheets.