Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended														3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended				9 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Constitution Pipeline Company Llc [Member]	Sep. 30, 2013 Bluegrass Pipeline Company Llc [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Cash and Cash Equivalents [Member]	Dec. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member] Cash and Cash Equivalents [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Property Plant And Equipment [Member]	Dec. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member] Property Plant And Equipment [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Accounts Payable [Member]	Dec. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member] Accounts Payable [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Accrued Liabilities [Member]	Dec. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member] Accrued Liabilities [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Other Noncurrent Liabilities [Member]	Dec. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member] Other Noncurrent Liabilities [Member]	Jun. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Gulfstar One [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Gulfstar One [Member]	Jun. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Constitution Pipeline Company Llc [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Constitution Pipeline Company Llc [Member]	Sep. 30, 2013 Variable Interest Entity, Primary Beneficiary [Member] Bluegrass Pipeline Company Llc [Member]	Sep. 30, 2013 Variable Interest Entity, Not Primary Beneficiary [Member] Laurel Mountain [Member]	Sep. 30, 2013 Variable Interest Entity, Not Primary Beneficiary [Member] Laurel Mountain [Member] Equity Method Investments [Member]	Sep. 30, 2013 Variable Interest Entity, Not Primary Beneficiary [Member] Caiman Energy II LLC [Member]	Sep. 30, 2013 Variable Interest Entity, Not Primary Beneficiary [Member] Caiman Energy II LLC [Member] Equity Method Investments [Member]	Sep. 30, 2013 Variable Interest Entity, Not Primary Beneficiary [Member] Moss Lake Fractionation Llc [Member]	Sep. 30, 2013 Variable Interest Entity, Not Primary Beneficiary [Member] Moss Lake Fractionation Llc [Member] Equity Method Investments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage			41.00%	50.00%												51.00%		41.00%	50.00%	51.00%		47.50%		50.00%
Estimated remaining construction costs																$ 400		$ 625	$ 140
Contributions from noncontrolling interests	327	4													187		4
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners															49.00%		10.00%
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets					58	8	897	556
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities									(135)	(128)	(2)	0	(110)	(109)
Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure [Abstract]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net																					492		257		2
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount																				$ 492		$ 380		$ 52