Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Amount of loss contingency liability.

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Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
Contingencies - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Loss contingency accrual	$ 5,300,000,000	$ 854,000,000
Other Assets	2,310,000,000us-gaap_OtherAssetsNoncurrent	2,082,000,000us-gaap_OtherAssetsNoncurrent
Decommissioning charge	4,360,000,000us-gaap_LossContingencyLossInPeriod	850,000,000us-gaap_LossContingencyLossInPeriod	(250,000,000)us-gaap_LossContingencyLossInPeriod
Liability for remediation and reclamation obligations	126,000,000	126,000,000
Landfill in West Covina, California [Member]
Loss Contingencies [Line Items]
Liability for remediation and reclamation obligations	50,000,000
Third Party Bankruptcy Assignment [Member]
Loss Contingencies [Line Items]
Decommissioning charge	22,000,000	117,000,000
Decommissioning obligations included in accrued expenses	114,000,000
Pending Litigation [Member] \| Peregrino Litigation [Member]
Loss Contingencies [Line Items]
Loss contingency accrual	0
Pending Litigation [Member] \| Amount Of Tax Originally In Dispute [Member] \| Peregrino Litigation [Member]
Loss Contingencies [Line Items]
Other Assets	128,000,000
Pending Litigation [Member] \| Amount Of Tax Currently In Dispute [Member] \| Peregrino Litigation [Member]
Loss Contingencies [Line Items]
Other Assets	$ 42,000,000