Unconsolidated Affiliates (Details) (USD $)	2 Months Ended	3 Months Ended		6 Months Ended											3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		2 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended		3 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	May 01, 2013	Dec. 31, 2012	Jun. 30, 2013 SESH [Member]	Dec. 31, 2012 SESH [Member]	Jun. 30, 2013 Midstream Partnership [Member]	May 01, 2013 Midstream Partnership [Member]	Dec. 31, 2012 Midstream Partnership [Member]	Jun. 30, 2013 Other Entity [Member]	Dec. 31, 2012 Other Entity [Member]	Jun. 30, 2013 Other Entity [Member]	Jun. 30, 2012 Other Entity [Member]	Jun. 30, 2013 Other Entity [Member]	Jun. 30, 2012 Other Entity [Member]	Jun. 30, 2013 SESH [Member]	Jun. 30, 2012 SESH [Member]	Jun. 30, 2013 SESH [Member]	Jun. 30, 2012 SESH [Member]	Jun. 30, 2013 Midstream Partnership [Member]	Jun. 30, 2013 Midstream Partnership [Member]	Jun. 30, 2012 Midstream Partnership [Member]	Jun. 30, 2013 Midstream Partnership [Member]	Jun. 30, 2012 Midstream Partnership [Member]	Apr. 30, 2013 Southeast Supply Header Llc [Member] CERC Corp [Member]	Apr. 30, 2013 Enogex LLC [Member] OGE ARCLIGHT [Member]	Jun. 30, 2013 Senior Subordinated Notes [Member] CERC Corp [Member]
Equity Method Investment, Summarized Financial Information, Revenue																							$ 502,000,000
Equity in earnings of unconsolidated affiliates		37,000,000	8,000,000	42,000,000	17,000,000										0	2,000,000	0	5,000,000	4,000,000	6,000,000	9,000,000	12,000,000		33,000,000	0	33,000,000	0
Equity Method Investment, Ownership Percentage								25.05%		58.30%
Equity Interest Contributed, Percentage																												24.95%	100.00%
Contributed Assets						5,800,000,000
Contributed Liabilities						1,500,000,000
Debt repayment by affiliate											1,050,000,000
Debt repayment by affiliate						1,050,000,000
Debt of Affiliate											363,000,000
Investment in unconsolidated affiliates	4,485,000,000	4,485,000,000		4,485,000,000			405,000,000	200,000,000	404,000,000	4,285,000,000	4,300,000,000	0	0	1,000,000
Transitional Service Costs to be Reimbursed	28,000,000
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)																							207,000,000
Equity Method Investment, Summarized Fnancial Information, Operating Income																							75,000,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)																							65,000,000
Gross equity in earnings																							38,000,000
Basis Difference Amortization																							(5,000,000)
Equity Earnings Net of Basis Difference Amortization																							$ 33,000,000
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum																														2.10%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum																														2.45%