Revenue from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	[1]	$ 848.2	$ 687.8	$ 3,033.7	$ 1,600.2
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		365.5	294.9	1,112.2	664.6
Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		203.4	156.7	619.2	361.0
Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		79.9	59.3	264.1	145.5
Oilfield
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		68.0	50.6	257.5	127.2
Public authorities and street light
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		75.0	57.8	235.1	133.1
System sales revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		791.8	619.3	2,488.1	1,431.4
Provision for rate refund
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0.0	4.8	0.0	3.2
Integrated market
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		17.2	18.0	447.6	33.7
Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		30.8	35.0	103.8	109.0
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		$ 8.4	$ 10.7	$ (5.8)	$ 22.9

[1] In February 2021, Winter Storm Uri resulted in record winter peak demand for electricity and extremely high natural gas and purchased power prices in OG&E's service territory. Operating revenues for the nine months ended September 30, 2021 significantly increased due to increased fuel, purchased power and direct transmission expenses, which are generally recoverable from customers, as a result of Winter Storm Uri. For further discussion, see Note 15 and "Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operation."