Contingencies - Deepwater Horizon Events (Detail) (USD $)	3 Months Ended		9 Months Ended								9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2011 Macondo Exploration Well [Member]	Sep. 30, 2014 Deepwater Horizon [Member] Pending Litigation [Member]	Dec. 31, 2013 Deepwater Horizon [Member] Pending Litigation [Member]	Sep. 30, 2014 Deepwater Horizon [Member] Pending Litigation [Member] BP and BPAP [Member]	Sep. 30, 2014 Deepwater Horizon [Member] Pending Litigation [Member] Transocean [Member]	Sep. 30, 2014 Deepwater Horizon [Member] Pending Litigation [Member] Halliburton Energy Services [Member]	Sep. 30, 2014 Deepwater Horizon [Member] Pending Litigation [Member] Clean Water Act [Member]	Jun. 30, 2014 Deepwater Horizon [Member] Pending Litigation [Member] Clean Water Act [Member]	Sep. 30, 2014 Deepwater Horizon [Member] BP indemnification liability [Member]
Loss Contingencies [Line Items]
Anadarko's nonoperated interest					25.00%
Loss contingency accrual													$ 0
Litigation-related contingent liability						93,000,000	0				90,000,000	90,000,000
Deepwater Horizon settlement and related costs	$ 3,000,000	$ 5,000,000	$ 96,000,000	$ 12,000,000							$ 90,000,000
Allocation of fault assigned in Phase I Findings and Conclusions						0.00%		67.00%	30.00%	3.00%