Equity-Method Investments (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2007
Schedule of Equity Method Investments [Line Items]
Carrying amount of investments	$ 2,800,000,000
Equity earnings from Anadarko's investments in the investee entities	(43,000,000)	(41,000,000)	(37,000,000)
Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Fair value of oil and gas properties and gathering and processing assets contributed by Anadarko				2,900,000,000
Ownership interest of investee entities	95.00%
Loan from investee entities				2,900,000,000
Carrying amount of notes payable to affiliates	2,900,000,000
Applicable interest rate	1.31%	1.55%
Interest expense on the notes payable	$ 42,000,000	$ 38,000,000	$ 39,000,000
Equity Method Investments [Member] | Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Debt-to-capital ratio covenant	0.67