Results of Operations for Oil and Gas Producing Activities (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Revenues
Total oil and gas revenues	$ 5,306,300,000	[1]	$ 4,599,600,000	[1]	$ 4,205,400,000	[1]
Other operating revenues	6,300,000	[1]	8,500,000	[1]	39,900,000	[1]
Total revenues	5,312,600,000	[1]	4,608,100,000	[1]	4,245,300,000	[1]
Costs and expenses
Production expenses	1,340,200,000	[1]	1,114,800,000	[1]	1,010,300,000	[1]
Exploration costs charged to expense	435,300,000	[1]	251,100,000	[1]	371,200,000	[1]
Undeveloped lease amortization	66,900,000	[1]	129,800,000	[1]	118,200,000	[1]
Depreciation, depletion and amortization	1,543,600,000	[1]	1,244,400,000	[1]	956,000,000	[1]
Accretion of asset retirement obligations	49,000,000	[1]	38,400,000	[1]	33,800,000	[1]
Impairment of properties	21,587,000	[1]	200,000,000	[1],[2]	368,600,000	[1],[2]
Terra Nova working interest redetermination	0		0	[2]	(5,351,000)	[1],[2]
Selling and general expenses	170,900,000	[1]	119,600,000	[1]	97,600,000	[1]
Total costs and expenses	3,627,500,000	[1]	3,098,100,000	[1]	2,950,300,000	[1]
Results of Operations, Income before Income Taxes	1,685,100,000	[1]	1,510,000,000	[1]	1,295,000,000	[1]
Income tax expense	656,300,000	[1]	605,000,000	[1]	680,800,000	[1]
Results of operations	1,028,800,000	[1]	905,000,000	[1]	614,200,000	[1]
Crude Oil and Natural Gas Liquids [Member]
Revenues
Sales to unaffiliated enterprises	4,631,500,000	[1]	3,854,500,000	[1]	3,392,800,000	[1]
Transfers to consolidated operations					142,800,000	[1]
Natural Gas [Member]
Revenues
Sales to unaffiliated enterprises	674,800,000	[1]	745,100,000	[1]	812,600,000	[1]
United States [Member] | Oil Reserves [Member]
Revenues
Total oil and gas revenues	1,797,400,000	[1]	1,030,300,000	[1]	719,900,000	[1]
Other operating revenues	6,400,000	[1]	7,700,000	[1]	17,800,000	[1]
Total revenues	1,803,800,000	[1]	1,038,000,000	[1]	737,700,000	[1]
Costs and expenses
Production expenses	351,100,000	[1]	252,400,000	[1]	164,800,000	[1]
Exploration costs charged to expense	75,200,000	[1]	51,900,000	[1]	36,500,000	[1]
Undeveloped lease amortization	30,300,000	[1]	71,600,000	[1]	62,200,000	[1]
Depreciation, depletion and amortization	576,300,000	[1]	330,200,000	[1]	183,000,000	[1]
Accretion of asset retirement obligations	13,500,000	[1]	11,400,000	[1]	9,900,000	[1]
Impairment of properties	0	[1]	0	[1]	0	[1]
Terra Nova working interest redetermination					0	[1]
Selling and general expenses	80,400,000	[1]	52,700,000	[1]	42,100,000	[1]
Total costs and expenses	1,126,800,000	[1]	770,200,000	[1]	498,500,000	[1]
Results of Operations, Income before Income Taxes	677,000,000	[1]	267,800,000	[1]	239,200,000	[1]
Income tax expense	241,600,000	[1]	99,800,000	[1]	86,500,000	[1]
Results of operations	435,400,000	[1]	168,000,000	[1]	152,700,000	[1]
United States [Member] | Crude Oil and Natural Gas Liquids [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	1,724,700,000	[1]	976,100,000	[1]	648,800,000	[1]
Transfers to consolidated operations					0	[1]
United States [Member] | Natural Gas [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	72,700,000	[1]	54,200,000	[1]	71,100,000	[1]
Canada [Member] | Conventional [Member]
Revenues
Total oil and gas revenues	705,300,000	[1]	621,500,000	[1]	785,800,000	[1]
Other operating revenues	(1,900,000)	[1]	(900,000)	[1]	(3,800,000)	[1]
Total revenues	703,400,000	[1]	620,600,000	[1]	782,000,000	[1]
Costs and expenses
Production expenses	185,500,000	[1]	167,200,000	[1]	151,200,000	[1]
Exploration costs charged to expense	32,800,000	[1]	10,500,000	[1]	60,800,000	[1]
Undeveloped lease amortization	21,000,000	[1]	29,300,000	[1]	28,800,000	[1]
Depreciation, depletion and amortization	319,200,000	[1]	290,500,000	[1]	273,900,000	[1]
Accretion of asset retirement obligations	5,900,000	[1]	5,100,000	[1]	4,900,000	[1]
Impairment of properties	21,587,000	[1]	0	[1]	0	[1]
Terra Nova working interest redetermination					(5,400,000)	[1]
Selling and general expenses	25,300,000	[1]	19,700,000	[1]	14,200,000	[1]
Total costs and expenses	611,300,000	[1]	522,300,000	[1]	528,400,000	[1]
Results of Operations, Income before Income Taxes	92,100,000	[1]	98,300,000	[1]	253,600,000	[1]
Income tax expense	19,900,000	[1]	25,100,000	[1]	79,700,000	[1]
Results of operations	72,200,000	[1]	73,200,000	[1]	173,900,000	[1]
Canada [Member] | Synthetic Oil [Member]
Revenues
Total oil and gas revenues	441,000,000	[1]	463,100,000	[1]	506,600,000	[1]
Other operating revenues	300,000	[1]	600,000	[1]	0	[1]
Total revenues	441,300,000	[1]	463,700,000	[1]	506,600,000	[1]
Costs and expenses
Production expenses	228,200,000	[1]	224,100,000	[1]	236,100,000	[1]
Exploration costs charged to expense	0	[1]	0	[1]	0	[1]
Undeveloped lease amortization	0	[1]	0	[1]	0	[1]
Depreciation, depletion and amortization	55,400,000	[1]	55,300,000	[1]	52,100,000	[1]
Accretion of asset retirement obligations	10,300,000	[1]	8,500,000	[1]	7,600,000	[1]
Impairment of properties	0	[1]	0	[1]	0	[1]
Terra Nova working interest redetermination					0	[1]
Selling and general expenses	900,000	[1]	900,000	[1]	900,000	[1]
Total costs and expenses	294,800,000	[1]	288,800,000	[1]	296,700,000	[1]
Results of Operations, Income before Income Taxes	146,500,000	[1]	174,900,000	[1]	209,900,000	[1]
Income tax expense	37,900,000	[1]	40,000,000	[1]	55,800,000	[1]
Results of operations	108,600,000	[1]	134,900,000	[1]	154,100,000	[1]
Canada [Member] | Crude Oil and Natural Gas Liquids [Member] | Conventional [Member]
Revenues
Sales to unaffiliated enterprises	507,200,000	[1]	411,700,000	[1]	505,600,000	[1],[2]
Transfers to consolidated operations					46,400,000	[1]
Canada [Member] | Crude Oil and Natural Gas Liquids [Member] | Synthetic Oil [Member]
Revenues
Sales to unaffiliated enterprises	441,000,000	[1]	463,100,000	[1]	506,600,000	[1],[2]
Transfers to consolidated operations					96,400,000	[1]
Canada [Member] | Natural Gas [Member] | Conventional [Member]
Revenues
Sales to unaffiliated enterprises	198,100,000	[1]	209,800,000	[1]	280,200,000	[1]
Canada [Member] | Natural Gas [Member] | Synthetic Oil [Member]
Revenues
Sales to unaffiliated enterprises	0	[1]	0	[1]	0	[1]
Malaysia [Member] | Oil Reserves [Member]
Revenues
Total oil and gas revenues	2,279,000,000	[1]	2,427,100,000	[1]	2,044,300,000	[1]
Other operating revenues	1,500,000	[1]	1,000,000	[1]	1,300,000	[1]
Total revenues	2,280,500,000	[1]	2,428,100,000	[1]	2,045,600,000	[1]
Costs and expenses
Production expenses	384,400,000	[1]	422,700,000	[1]	420,600,000	[1]
Exploration costs charged to expense	25,300,000	[1]	27,200,000	[1]	11,100,000	[1]
Undeveloped lease amortization	0	[1]	0	[1]	0	[1]
Depreciation, depletion and amortization	588,200,000	[1]	532,100,000	[1]	357,300,000	[1]
Accretion of asset retirement obligations	15,000,000	[1]	12,500,000	[1]	10,600,000	[1]
Impairment of properties	0	[1]	0	[1]	0	[1]
Terra Nova working interest redetermination					0	[1]
Selling and general expenses	3,500,000	[1]	(5,300,000)	[1]	(1,600,000)	[1]
Total costs and expenses	1,016,400,000	[1]	989,200,000	[1]	798,000,000	[1]
Results of Operations, Income before Income Taxes	1,264,100,000	[1]	1,438,900,000	[1]	1,247,600,000	[1]
Income tax expense	477,700,000	[1]	544,700,000	[1]	434,900,000	[1]
Results of operations	786,400,000	[1]	894,200,000	[1]	812,700,000	[1]
Malaysia [Member] | Crude Oil and Natural Gas Liquids [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	1,875,000,000	[1]	1,946,000,000	[1]	1,583,000,000	[1]
Transfers to consolidated operations					0	[1]
Malaysia [Member] | Natural Gas [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	404,000,000	[1]	481,100,000	[1]	461,300,000	[1]
Republic of the Congo [Member] | Oil Reserves [Member]
Revenues
Total oil and gas revenues	83,600,000	[1]	57,600,000	[1]	148,800,000	[1]
Other operating revenues	(100,000)	[1]	0	[1]	0	[1]
Total revenues	83,500,000	[1]	57,600,000	[1]	148,800,000	[1]
Costs and expenses
Production expenses	191,000,000	[1]	48,400,000	[1]	37,600,000	[1]
Exploration costs charged to expense	5,800,000	[1]	76,800,000	[1]	21,000,000	[1]
Undeveloped lease amortization	0	[1]	0	[1]	0	[1]
Depreciation, depletion and amortization	200,000	[1]	33,900,000	[1]	87,800,000	[1]
Accretion of asset retirement obligations	4,300,000	[1]	900,000	[1]	500,000	[1]
Impairment of properties	0	[1]	200,000,000	[1]	368,600,000	[1]
Terra Nova working interest redetermination					0	[1]
Selling and general expenses	1,100,000	[1]	3,200,000	[1]	2,200,000	[1]
Total costs and expenses	202,400,000	[1]	363,200,000	[1]	517,700,000	[1]
Results of Operations, Income before Income Taxes	(118,900,000)	[1]	(305,600,000)	[1]	(368,900,000)	[1]
Income tax expense	(109,900,000)	[1]	(64,500,000)	[1]	16,400,000	[1]
Results of operations	(9,000,000)	[1]	(241,100,000)	[1]	(385,300,000)	[1]
Republic of the Congo [Member] | Crude Oil and Natural Gas Liquids [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	83,600,000	[1]	57,600,000	[1]	148,800,000	[1]
Transfers to consolidated operations					0	[1]
Republic of the Congo [Member] | Natural Gas [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	0	[1]	0	[1]	0	[1]
Other Regions [Member] | Oil Reserves [Member]
Revenues
Total oil and gas revenues	0	[1]	0	[1]	0	[1]
Other operating revenues	100,000	[1]	100,000	[1]	24,600,000	[1]
Total revenues	100,000	[1]	100,000	[1]	24,600,000	[1]
Costs and expenses
Production expenses	0	[1]	0	[1]	0	[1]
Exploration costs charged to expense	296,200,000	[1]	84,700,000	[1]	241,800,000	[1]
Undeveloped lease amortization	15,600,000	[1]	28,900,000	[1]	27,200,000	[1]
Depreciation, depletion and amortization	4,300,000	[1]	2,400,000	[1]	1,900,000	[1]
Accretion of asset retirement obligations	0	[1]	0	[1]	300,000	[1]
Impairment of properties	0	[1]	0	[1]	0	[1]
Terra Nova working interest redetermination					0	[1]
Selling and general expenses	59,700,000	[1]	48,400,000	[1]	39,800,000	[1]
Total costs and expenses	375,800,000	[1]	164,400,000	[1]	311,000,000	[1]
Results of Operations, Income before Income Taxes	(375,700,000)	[1]	(164,300,000)	[1]	(286,400,000)	[1]
Income tax expense	(10,900,000)	[1]	(40,100,000)	[1]	7,500,000	[1]
Results of operations	(364,800,000)	[1]	(124,200,000)	[1]	(293,900,000)	[1]
Other Regions [Member] | Crude Oil and Natural Gas Liquids [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	0	[1]	0	[1]	0	[1]
Transfers to consolidated operations					0	[1]
Other Regions [Member] | Natural Gas [Member] | Oil Reserves [Member]
Revenues
Sales to unaffiliated enterprises	$ 0	[1]	$ 0	[1]	$ 0	[1]

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

[2] Reclassified to conform to current presentation.