Contingencies - Deepwater Horizon Events (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Feb. 20, 2015	Jun. 30, 2014
Loss Contingencies [Line Items]
Loss contingency accrual	$ 5,300,000,000	$ 854,000,000
Accrual for environmental loss contingencies	126,000,000	126,000,000
Gain (loss) related to litigation settlement	(97,000,000)	(15,000,000)	(18,000,000)
Macondo Exploration Well [Member]
Loss Contingencies [Line Items]
Anadarko's nonoperated interest					25.00%
Deepwater Horizon [Member] | Oil Pollution Act of 1990 [Member]
Loss Contingencies [Line Items]
Allocable percentage share of gross OPA-related environmental costs	0.00%
Accrual for environmental loss contingencies	0
Deepwater Horizon [Member] | Oil Pollution Act of 1990 [Member] | BP Exploration and Production Inc. [Member]
Loss Contingencies [Line Items]
Gross OPA-related environmental costs, excluding amounts BP has already funded, amounts that cannot reasonably be estimated by BP, non-OPA-related fines and penalties, and estimated state and local governmental claims	11,000,000,000
Deepwater Horizon [Member] | BP indemnification liability [Member]
Loss Contingencies [Line Items]
Loss contingency accrual	0
Deepwater Horizon [Member] | Settled Litigation [Member]
Loss Contingencies [Line Items]
Cash payment for Deepwater Horizon settlement				4,000,000,000
Deepwater Horizon [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Penalties or fines assessed against the Company						0
Litigation-related contingent liability	90,000,000	0
Allocation of fault assigned in Phase One Findings and Conclusions	0.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | BP and BPAP [Member]
Loss Contingencies [Line Items]
Allocation of fault assigned in Phase One Findings and Conclusions	67.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | Transocean [Member]
Loss Contingencies [Line Items]
Allocation of fault assigned in Phase One Findings and Conclusions	30.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | Halliburton Energy Services [Member]
Loss Contingencies [Line Items]
Allocation of fault assigned in Phase One Findings and Conclusions	3.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | Clean Water Act [Member]
Loss Contingencies [Line Items]
Litigation-related contingent liability	90,000,000						90,000,000
Gain (loss) related to litigation settlement	$ (90,000,000)