Investment in Unconsolidated Affiliates (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended			3 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended			3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Enogex LLC [Member]	Jun. 30, 2014 Southeast Supply Header, LLC [Member]	Jun. 30, 2014 ArcLight group [Member]	Jun. 30, 2014 OGE Holdings [Member]	May 30, 2014 OGE Energy [Member]	Jun. 30, 2014 OGE Energy [Member]	Mar. 31, 2014 OGE Energy [Member]	Jun. 30, 2014 CenterPoint [Member]	Jun. 30, 2014 Enable Midstream Partners [Member]	Jun. 30, 2014 Enable Midstream Partners [Member]
Percentage of Enogex LLC Contributed		100.00%
Percentage of Subsidiary Contributed			24.95%
Partners' Capital Account, Units, Acquisitions	6,322,457
Percentage Share of Management Rights							50.00%		50.00%
Contributions to Pay Down Short-Term Debt				$ 107.0	$ 9.1
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	6.00%					26.70%	26.30%	28.50%
Units Held by Limited Partners of the LLC or LP.					42,832,291
Percent of Incentive Distribution Rights							60.00%		40.00%
Partners' Capital Account, Units, Sold in Public Offering				3,750,000						25,000,000
Proceeds from Issuance Initial Public Offering										464.0
Distributions from unconsolidated affiliates										$ 44.0	$ 76.5