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Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Related Party Transaction [Line Items]
Dividends, Common Stock			$ 0.0	$ 0.0
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	$ 33.9	$ 33.1	67.6	67.7
OG&E [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	3.6	3.3	7.6	5.5
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	17.5	17.5
OG&E [Member] \| Natural Gas Purchases [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	$ 2.2	$ (0.4)	$ 2.5	$ (0.8)