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Investment in Unconsolidated Affiliates Related Party Transactions (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Distribution Made to Limited Partner, Distributions Declared, Per Unit			$ 0.16525	$ 0.33050
Enable Midstream Partners [Member] \| OG&E [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	$ 4.5	$ 4.5	$ 11.7	$ 12.1
Operating Costs Charged [Member] \| Enable Midstream Partners [Member] \| OGE Energy [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	0.1	0.1	0.3	0.3
Employment Costs [Member] \| Enable Midstream Partners [Member] \| OGE Energy [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	3.5	3.6	13.6	20.0
Natural Gas Transportation [Member] \| Enable Midstream Partners [Member] \| OG&E [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	9.3	9.4	23.4	33.5
Natural Gas Purchases [Member] \| Enable Midstream Partners [Member] \| OG&E [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	3.2	$ (1.1)	2.2	$ (5.4)
Excluding Fuel Purchases [Member]
Related Party Transaction [Line Items]
Accounts receivable - unconsolidated affiliates	$ 1.4		$ 1.4		$ 0.8