Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	$ 10,475,149		$ 10,367,847
Property, plant and equipment, Cost	17,336,643		16,408,843
Exploration and Production Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	8,730,124	[1],[2]	7,898,417	[1],[2]
Property, plant and equipment, Cost	14,766,637	[1]	12,506,579	[1]
Refining and Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	1,688,709		2,409,410
Property, plant and equipment, Cost	2,456,822		3,794,223
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Net	56,316		60,020
Property, plant and equipment, Cost	$ 113,184		$ 108,041

[1] Includes mineral rights as follows: $ 1,078,770 619,950 779,036 432,051

[2] Includes $21,154 in 2011 and $17,067 in 2010 related to administrative assets and support equipment.