Reconciliation of Income Taxes Based on U.S. Statutory Tax Rate to Income Tax Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income tax expense based on the U.S. statutory tax rate	$ 542,844	$ 486,049		$ 432,395
Foreign income subject to foreign taxes at a rate different than the U.S. statutory rate	10,053	56,367		33,395
State income taxes, net of federal benefit	19,742	10,066		4,607
Increase in deferred tax asset valuation allowance related to foreign exploration expenditures	102,714	47,128		34,431
Impairment of Azurite field with no tax benefit	129,010	0		0
Malaysian tax benefits on prior year costs in Block P	(25,573)	0		0
Increase in United Kingdom oil and gas tax rate	14,461	0		0
Other, net	16,800	9,541		16,731
Total	$ 810,051	$ 609,151	[1]	$ 521,559	[1]

[1] Reclassified to conform to current presentation.