Derivative Instruments and Hedging Activities, Income Statement Presentation Related to Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ (0.2)
Enogex [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Other Comprehensive Income	0.5	[1]	(5.5)	(22.9)
Amount Reclassifed from Accumulated Other Comprehensive Income (Loss) into Income	4.8		(40.6)	(28.8)
Amount Recognized in Income	0		0	0.2
Enogex [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income	(10.6)		(9.6)	(8.5)
Enogex [Member] | NGLs [Member] | Options [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Other Comprehensive Income			(8.4)	(9.7)
Amount Reclassifed from Accumulated Other Comprehensive Income (Loss) into Income			(9.8)	1.2
Amount Recognized in Income			0	0
Enogex [Member] | NGLs [Member] | Fixed Swaps/Futures [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Other Comprehensive Income				1.7
Amount Reclassifed from Accumulated Other Comprehensive Income (Loss) into Income				(3.7)
Amount Recognized in Income				0
Enogex [Member] | Natural gas [Member] | Fixed Swaps/Futures [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Other Comprehensive Income	0.5	[1]	2.9	(14.9)
Amount Reclassifed from Accumulated Other Comprehensive Income (Loss) into Income	5.2		(30.4)	(25.9)
Amount Recognized in Income	0		0	0.2
Enogex [Member] | Natural gas [Member] | Fixed Swaps/Futures [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income	1.1		0.4	3.2
Enogex [Member] | Sales [Member] | Natural gas [Member] | Physical [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income	(11.7)		(10.0)	(11.7)
OGE Energy Corp. [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Other Comprehensive Income	0	[1]	0	0
Amount Reclassifed from Accumulated Other Comprehensive Income (Loss) into Income	(0.4)		(0.4)	(0.4)
Amount Recognized in Income	0		0	0
Maximum [Member] | Enogex [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Additional Collateral, Aggregate Fair Value	$ 0.2

[1] The estimated net amount of gains or losses included in Accumulated Other Comprehensive Income (Loss) at December 31, 2012 that is expected to be reclassified into income within the next 12 months is a loss of $0.2 million.