Investment in Unconsolidated Affiliate and Related Party Transactions Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Expected Settlement Charge	$ 14.6
Accounts receivable - unconsolidated affiliates	1.9	$ 2.5
Og and E [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	14.0	11.5	$ 13.8
Operating Costs Charged [Member] \| OGE Energy [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	2.3	4.7	12.4
Natural Gas Transportation [Member] \| Og and E [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	35.0	35.0	35.0
Natural Gas Purchases [Member] \| Og and E [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	(2.1)	11.2	7.6
Employment Costs [Member] \| OGE Energy [Member] \| Enable Midstream Partners [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	29.5	28.7	$ 32.7
Excluding Fuel Purchases [Member]
Related Party Transaction [Line Items]
Accounts receivable - unconsolidated affiliates	$ 2.0	$ 2.7

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
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-Section 50
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-Section S99
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
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-Name Accounting Standards Codification
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