Short-Term Debt and Credit Facilities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Advances from parent	$ 0.0	$ 49.9
Advances to parent	$ 86.0	$ 0.0
Ratio of Consolidated Debt to Consolidated Capitalization	65.00%
OG&E [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 450.0
Debt Restriction Maximum Letters of Credit	100.0
Available Optional Increase of Borrowing Capacity in Credit Facility	150.0
Intercomany Borrowings, Maximum Borrowing Capacity	350.0
Outstanding Intercompany Borrowings	0.0
Aggregate Commitment - Revolving Credit Facility	$ 600.0
Intercompany Borrowing Agreement, Expiration Date	Mar. 08, 2022
Letters of Credit Outstanding	$ 1.8
Weighted Average Interest Rate	0.95%
Long-term Line of Credit	$ 0.0
Commercial Paper	0.0
Short Term Borrowing Capacity That Has Regulatory Approval	$ 800.0
Period For Which Regulatory Approval Has Been Given to Acquire Short Term Debt	2 years
Acceleration of Debt [Member] | OG&E [Member]
Short-term Debt [Line Items]
Acceleration of Indebtedness of Credit Facility	$ 100.0
Uninsured Judgements [Member] | OG&E [Member]
Short-term Debt [Line Items]
Acceleration of Indebtedness of Credit Facility	$ 100.0