Segment Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Disclosure [Line Items]
Interest expense, net of capitalization	$ 55,831,000		$ 53,172,000	[1]	$ 53,005,000	[1]
Income tax expense (benefit)	810,051,000		609,151,000	[1]	521,559,000	[1]
Significant noncash charges (credits)
Depreciation, depletion, amortization	1,093,406,000		1,114,529,000	[1]	870,999,000	[1]
Accretion of asset retirement obligations	37,701,000		31,857,000	[1]	26,154,000	[1]
Amortization of undeveloped leases	118,211,000		108,026,000	[1]	83,213,000	[1]
Impairment of long-lived assets	368,600,000	[2]			5,200,000	[2]
Deferred and noncurrent income taxes	171,565,000		135,225,000	[1]	95,245,000	[1]
Additions to property, plant, equipment	2,447,900,000		1,919,700,000		1,667,800,000
Total assets at year-end	14,138,138,000		14,233,243,000
United States
Significant noncash charges (credits)
Additions to property, plant, equipment	714,400,000		396,500,000		341,800,000
Canada
Significant noncash charges (credits)
Additions to property, plant, equipment	905,600,000		821,500,000		352,300,000
Malaysia
Significant noncash charges (credits)
Additions to property, plant, equipment	695,100,000		476,500,000		754,500,000
United Kingdom
Significant noncash charges (credits)
Additions to property, plant, equipment	30,500,000		6,000,000		15,000,000
Republic of the Congo
Significant noncash charges (credits)
Additions to property, plant, equipment	81,700,000		169,400,000		195,800,000
Exploration and production
Segment Reporting Disclosure [Line Items]
Segment income (loss)	625,700,000		806,900,000		691,800,000
Revenues from external customers	4,209,800,000		3,571,200,000		2,950,700,000
Intersegment revenues	142,800,000		118,900,000		85,300,000
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	727,600,000		576,900,000		476,100,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	969,700,000		1,005,000,000		775,800,000
Accretion of asset retirement obligations	36,800,000		31,100,000		25,500,000
Amortization of undeveloped leases	118,200,000		108,000,000		83,200,000
Impairment of long-lived assets	368,600,000				5,200,000
Deferred and noncurrent income taxes	192,000,000		119,100,000		64,800,000
Additions to property, plant, equipment	2,396,500,000		1,850,400,000		1,625,600,000
Total assets at year-end	10,347,000,000		9,182,700,000		8,196,300,000
Exploration and production | United States
Segment Reporting Disclosure [Line Items]
Segment income (loss)	152,700,000		72,700,000		178,000,000
Revenues from external customers	737,700,000		659,900,000		708,600,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	86,500,000		30,000,000		88,400,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	183,000,000		281,100,000		246,500,000
Accretion of asset retirement obligations	9,900,000		6,900,000		6,800,000
Amortization of undeveloped leases	62,200,000		68,500,000		34,700,000
Impairment of long-lived assets	0				5,200,000
Deferred and noncurrent income taxes	54,200,000		(48,600,000)		(4,600,000)
Additions to property, plant, equipment	696,600,000		369,400,000		336,800,000
Total assets at year-end	2,227,600,000		1,651,300,000		1,679,700,000
Exploration and production | Canada
Segment Reporting Disclosure [Line Items]
Segment income (loss)	328,000,000		213,800,000		64,800,000
Revenues from external customers	1,145,800,000		780,200,000		635,200,000
Intersegment revenues	142,800,000		118,900,000		85,300,000
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	135,500,000		79,100,000		21,000,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	326,000,000		225,500,000		199,900,000
Accretion of asset retirement obligations	12,500,000		11,200,000		8,600,000
Amortization of undeveloped leases	28,800,000		33,700,000		44,100,000
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	39,600,000		34,500,000		(7,200,000)
Additions to property, plant, equipment	885,200,000		804,400,000		330,100,000
Total assets at year-end	3,746,800,000		3,242,600,000		2,507,800,000
Exploration and production | Malaysia
Segment Reporting Disclosure [Line Items]
Segment income (loss)	812,700,000		659,400,000		561,900,000
Revenues from external customers	2,045,600,000		1,837,900,000		1,526,400,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	434,900,000		414,100,000		354,100,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	357,300,000		379,000,000		304,100,000
Accretion of asset retirement obligations	10,600,000		9,800,000		7,800,000
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	84,600,000		145,500,000		77,600,000
Additions to property, plant, equipment	694,800,000		467,900,000		739,000,000
Total assets at year-end	3,826,900,000		3,333,100,000		3,249,600,000
Exploration and production | United Kingdom
Segment Reporting Disclosure [Line Items]
Segment income (loss)	11,500,000		30,500,000		12,600,000
Revenues from external customers	107,300,000		133,600,000		61,600,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	46,800,000		32,600,000		11,900,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	13,700,000		22,400,000		12,400,000
Accretion of asset retirement obligations	3,000,000		2,300,000		1,600,000
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	14,600,000		(11,400,000)		(900,000)
Additions to property, plant, equipment	19,700,000		(4,700,000)		17,200,000
Total assets at year-end	214,100,000		187,900,000		209,000,000
Exploration and production | Republic of the Congo
Segment Reporting Disclosure [Line Items]
Segment income (loss)	(385,300,000)		(77,200,000)		(20,600,000)
Revenues from external customers	148,800,000		155,700,000		16,500,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	16,400,000		20,600,000		1,300,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	87,800,000		95,500,000		11,500,000
Accretion of asset retirement obligations	500,000		400,000		100,000
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	368,600,000				0
Deferred and noncurrent income taxes	(900,000)		(900,000)		0
Additions to property, plant, equipment	79,600,000		163,600,000		194,900,000
Total assets at year-end	257,500,000		678,900,000		516,700,000
Exploration and production | Other
Segment Reporting Disclosure [Line Items]
Segment income (loss)	(293,900,000)		(92,300,000)		(104,900,000)
Revenues from external customers	24,600,000		3,900,000		2,400,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	7,500,000		500,000		(600,000)
Significant noncash charges (credits)
Depreciation, depletion, amortization	1,900,000		1,500,000		1,400,000
Accretion of asset retirement obligations	300,000		500,000		600,000
Amortization of undeveloped leases	27,200,000		5,800,000		4,400,000
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	(100,000)		0		(100,000)
Additions to property, plant, equipment	20,600,000		49,800,000		7,600,000
Total assets at year-end	74,100,000		88,900,000		33,500,000
Refining and Marketing
Segment Reporting Disclosure [Line Items]
Segment income (loss)	190,300,000		130,600,000		45,000,000
Revenues from external customers	23,502,200,000		16,655,400,000		13,842,300,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	134,500,000		79,500,000		41,300,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	115,000,000		101,500,000		89,200,000
Accretion of asset retirement obligations	900,000		800,000		700,000
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	23,200,000		8,300,000		25,400,000
Additions to property, plant, equipment	122,300,000		290,100,000		263,400,000
Total assets at year-end	3,000,300,000		4,110,200,000		3,430,400,000
Refining and Marketing | United States
Segment Reporting Disclosure [Line Items]
Segment income (loss)	223,600,000		165,300,000		65,500,000
Revenues from external customers	17,471,900,000		13,750,400,000		11,116,400,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	146,600,000		101,800,000		42,300,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	68,300,000		60,100,000		55,400,000
Accretion of asset retirement obligations	900,000		800,000		700,000
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	28,500,000		5,100,000		9,500,000
Additions to property, plant, equipment	100,100,000		221,000,000		161,600,000
Total assets at year-end	1,806,500,000		2,996,600,000		2,490,600,000
Refining and Marketing | United Kingdom
Segment Reporting Disclosure [Line Items]
Segment income (loss)	(33,300,000)		(34,700,000)		(20,500,000)
Revenues from external customers	6,030,300,000		2,905,000,000		2,725,900,000
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	(12,100,000)		(22,300,000)		(1,000,000)
Significant noncash charges (credits)
Depreciation, depletion, amortization	46,700,000		41,400,000		33,800,000
Accretion of asset retirement obligations	0		0		0
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	(5,300,000)		3,200,000		15,900,000
Additions to property, plant, equipment	22,200,000		69,100,000		101,800,000
Total assets at year-end	1,193,800,000		1,113,600,000		939,800,000
Corporate and Other
Segment Reporting Disclosure [Line Items]
Segment income (loss)	(75,100,000)		(157,900,000)		(23,000,000)
Revenues from external customers	33,500,000		(56,900,000)		102,200,000
Intersegment revenues	0		0		0
Interest income	10,100,000		6,900,000		51,700,000
Interest expense, net of capitalization	40,700,000		34,700,000		24,400,000
Income tax expense (benefit)	(52,000,000)		(47,200,000)		4,200,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	8,700,000		8,000,000		6,000,000
Accretion of asset retirement obligations	0		0		0
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	(43,600,000)		7,800,000		5,000,000
Additions to property, plant, equipment	5,300,000		5,900,000		23,000,000
Total assets at year-end	790,800,000		940,300,000		1,129,700,000
Discontinued Operations
Segment Reporting Disclosure [Line Items]
Segment income (loss)	131,800,000		18,500,000		123,800,000
Revenues from external customers	0		0		0
Intersegment revenues	0		0		0
Interest income	0		0		0
Interest expense, net of capitalization	0		0		0
Income tax expense (benefit)	0		0		0
Significant noncash charges (credits)
Depreciation, depletion, amortization	0		0		0
Accretion of asset retirement obligations	0		0		0
Amortization of undeveloped leases	0		0		0
Impairment of long-lived assets	0				0
Deferred and noncurrent income taxes	0		0		0
Additions to property, plant, equipment	48,100,000		117,300,000		113,300,000
Total assets at year-end	0		0		0
Consolidated
Segment Reporting Disclosure [Line Items]
Segment income (loss)	872,700,000		798,100,000		837,600,000
Revenues from external customers	27,745,500,000		20,169,700,000		16,895,200,000
Intersegment revenues	142,800,000		118,900,000		85,300,000
Interest income	10,100,000		6,900,000		51,700,000
Interest expense, net of capitalization	40,700,000		34,700,000		24,400,000
Income tax expense (benefit)	810,100,000		609,200,000		521,600,000
Significant noncash charges (credits)
Depreciation, depletion, amortization	1,093,400,000		1,114,500,000		871,000,000
Accretion of asset retirement obligations	37,700,000		31,900,000		26,200,000
Amortization of undeveloped leases	118,200,000		108,000,000		83,200,000
Impairment of long-lived assets	368,600,000				5,200,000
Deferred and noncurrent income taxes	171,600,000		135,200,000		95,200,000
Additions to property, plant, equipment	2,572,200,000		2,263,700,000		2,025,300,000
Total assets at year-end	$ 14,138,100,000		$ 14,233,200,000		$ 12,756,400,000

[1] Reclassified to conform to current presentation.

[2] Results exclude corporate overhead, interest and discontinued operations.