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Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
Dividends, Common Stock			$ 185.0	$ 105.0
Operating Costs Charged [Member] \| OG&E [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	$ 35.1	$ 30.2	102.6	97.9
OG&E [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Electricity to power electric compression assets	4.7	4.5	12.2	10.0
OG&E [Member] \| Natural Gas Transportation [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from related party	8.8	8.8	26.3	26.3
OG&E [Member] \| Natural Gas Purchases [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from related party	$ 0.1	$ 0.4	$ 2.6	$ (0.4)