Investment in Unconsolidated Affiliates Reconciliation of Equity in Earnings of Unconsolidated Affiliates (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Reconciliation of Equity in Earnings of Unconsolidated Affiliates [Line Items]
Net income	$ 110.1	$ (985.1)	$ 230.8	$ (817.3)
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	761.5		761.5		$ 783.5
Timing Differences Related to Equity Method Investee Net Income	3.0	4.2	(3.6)	9.9
Net Income Used to Calculate Equity in Earnings	104.0	(980.9)	218.1	(807.4)
Proportionate Unconsolidated Affiliate Net Income	27.3	(257.2)	57.5	(212.0)
OGE Energy's share of Enable net income (loss)	27.3	(79.5)	58.1	(34.3)
Amortization of basis difference	(2.9)	(3.5)	8.8	(10.6)
Elimination of Enable fair value step up	(4.3)	(4.1)	12.6	(11.7)
Equity in earnings (loss) of unconsolidated affiliates	$ 34.5	$ (71.9)	$ 79.5	$ (12.0)
OGE Holdings [Member]
Reconciliation of Equity in Earnings of Unconsolidated Affiliates [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	26.30%	26.30%	26.30%	26.30%
OGE Energy [Member]
Reconciliation of Equity in Earnings of Unconsolidated Affiliates [Line Items]
Goodwill, Impairment Loss	$ 0.0	$ (177.7)	$ 0.6	$ (177.7)
Preferred Partner [Member]
Reconciliation of Equity in Earnings of Unconsolidated Affiliates [Line Items]
Distribution Made to Limited Partner, Cash Distributions Paid	$ (9.1)	$ 0.0	$ (9.1)	$ 0.0