Short-Term Debt and Credit Facility Short-Term Debt and Credit Facility (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Advances to parent	$ 333.6	$ 215.6
OG&E [Member]
Line of Credit Facility [Line Items]
Intercomany Borrowings, Maximum Borrowing Capacity	$ 400.0
Intercompany Borrowing Agreement, Expiration Date	Dec. 13, 2017
Outstanding Intercompany Borrowings	$ 0.0
Line of Credit Facility, Maximum Borrowing Capacity	400.0
Letters of Credit Outstanding, Amount	$ 1.9
Short-term Debt, Weighted Average Interest Rate	0.95%
Line of Credit Facility, Amount Outstanding	$ 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
December 13, 2017 [Member] | OG&E [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 8.7