Investment in Unconsolidated Affiliate and Related Party Transactions Reconciliation of Equity in Earnings of Unconsolidated Affiliates (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Equity Method Investments [Line Items]
OGE's share of Enable Net Income	$ 21.3	$ 23.8
Amortization of basis difference	2.9	3.5
Elimination of Enogex Holdings fair value and other adjustments	4.1	4.4
Equity in earnings of unconsolidated affiliates	28.3	31.7
Natural Gas Midstream Operations [Member]
Schedule of Equity Method Investments [Line Items]
Equity in earnings of unconsolidated affiliates	$ 28.3	$ 31.7