Derivative Instrument and Hedging Activities - Sch. of Der. Instruments in Stmt of Fin. Position, FV (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Asset Derivatives	$ 8	$ 2
Liability Derivatives	77	91
Cash Flow Hedges: [Member]
Derivative [Line Items]
Asset Derivatives	0	0
Liability Derivatives	3	5
Economic Hedges [Member]
Derivative [Line Items]
Asset Derivatives	8	2
Liability Derivatives	74	86
Economic Hedges [Member] | Interest rate contracts [Member] | Derivative instruments - liabilities [Member]
Derivative [Line Items]
Asset Derivatives	0	0
Liability Derivatives	18	18
Economic Hedges [Member] | Interest rate contracts [Member] | Deferred credits [Member]
Derivative [Line Items]
Asset Derivatives	0	0
Liability Derivatives	54	59
Gathering and Processing [Member] | Cash Flow Hedges: [Member] | Natural gas price swaps [Member] | Accounts payable - related parties [Member]
Derivative [Line Items]
Asset Derivatives	0	0
Liability Derivatives	3	5
Distribution [Member] | Economic Hedges [Member] | Natural gas price swaps [Member] | Assets Held-for-sale [Member]
Derivative [Line Items]
Asset Derivatives	8	1
Liability Derivatives	0	0
Distribution [Member] | Economic Hedges [Member] | Natural gas price swaps [Member] | Non-current assets held for sale [Member]
Derivative [Line Items]
Asset Derivatives	0	1
Liability Derivatives	0	0
Distribution [Member] | Economic Hedges [Member] | Natural gas price swaps [Member] | current liabilities held for sale [Member]
Derivative [Line Items]
Asset Derivatives	0	0
Liability Derivatives	$ 2	$ 9