Noncontrolling Interest Owner Distributions Made to Partners (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended	3 Months Ended				12 Months Ended	3 Months Ended				12 Months Ended
	Dec. 31, 2011 OGE Holdings [Member]	Sep. 30, 2011 OGE Holdings [Member]	Jun. 30, 2011 OGE Holdings [Member]	Mar. 31, 2011 OGE Holdings [Member]	Dec. 31, 2011 OGE Holdings [Member]	Dec. 31, 2011 Enogex Holdings [Member]	Sep. 30, 2011 Enogex Holdings [Member]	Jun. 30, 2011 Enogex Holdings [Member]	Mar. 31, 2011 Enogex Holdings [Member]	Dec. 31, 2011 Enogex Holdings [Member]	Dec. 31, 2011 ArcLight Group [Member]	Sep. 30, 2011 ArcLight Group [Member]	Jun. 30, 2011 ArcLight Group [Member]	Mar. 31, 2011 ArcLight Group [Member]	Dec. 31, 2011 ArcLight Group [Member]	Nov. 01, 2011 ArcLight Group [Member]	Oct. 03, 2011 ArcLight Group [Member]	Feb. 01, 2011 ArcLight Group [Member]
Distribution Made to Partners [Line Items]
Contributions Towards Meeting 2011 Capital Requirements																$ 53.0	$ 90.0	$ 71.6
Distributions to partners	$ 30.4	$ 43.4	$ 34.3	$ 7.5	$ 115.6	$ 35.1	$ 50.0	$ 39.6	$ 8.3	$ 133.0	$ 4.7	$ 6.6	$ 5.3	$ 0.8	$ 17.4