Property, Plant and Equipment - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Total capitalized exploratory well costs	$ 445,697,000	$ 556,412,000		$ 497,765,000		$ 369,862,000
Exploratory well costs capitalized more than one year	385,864,000
Impairment of long-lived assets	260,988,000	368,600,000	[1]	0	[1]
Ethanol Plant in Hereford, Texas
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Impairment of long-lived assets	60,988,000
Malaysia
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory well costs capitalized more than one year	270,093,000
United States
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Exploratory well costs capitalized more than one year	$ 115,771,000

[1] Reclassified to conform to current presentation.