Noncontrolling Interests Distributions Made to Partners (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
OGE Holdings [Member]
Distribution Made to Partners [Line Items]
Distributions to partners	$ 10.0
ArcLight group [Member]
Distribution Made to Partners [Line Items]
Distributions to partners	2.5
Enogex Holdings [Member]
Distribution Made to Partners [Line Items]
Distributions to partners	12.5
Atoka [Member]
Distribution Made to Partners [Line Items]
Distributions to partners	$ 0