Cost Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	$ 493.7	[1]	$ 448.0	[1]	$ 562.5	[1]
Development costs	3,939.6	[1]	3,521.7	[1]	1,954.3	[1]
Total Costs	4,482.1		4,413.7		2,819.6
United States [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	112.4	[1]	174.5	[1]	253.2	[1]
Development costs	1,773.2	[1]	1,352.7	[1]	263.9	[1]
Total Costs	1,931.2		1,704.0		750.9
Canada [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	21.8	[1]	57.0	[1]	76.0	[1]
Development costs	351.6	[1]	664.5	[1]	871.9	[1]
Total Costs	373.4		978.5		966.4
Malaysia [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	14.9	[1]	68.8	[1]	0.7	[1]
Development costs	1,787.7	[1],[2]	1,433.7	[1]	705.5	[1]
Total Costs	1,802.6		1,502.5		706.2
Non-cash capital lease obligation	358.0
United Kingdom [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0	[1],[3]	(1.0)	[1],[3]	0.5	[1],[3]
Development costs	8.1	[1],[3]	46.6	[1],[3]	30.5	[1],[3]
Total Costs	8.1	[3]	45.6	[3]	31.0	[3]
Republic of the Congo [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0.1	[1]	51.1	[1]	0.5	[1]
Development costs	0	[1]	22.6	[1]	78.7	[1]
Total Costs	0.1		73.7		102.7
Other Regions [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	344.5	[1]	97.6	[1]	231.6	[1]
Development costs	19.0	[1]	1.6	[1]	3.8	[1]
Total Costs	366.7		109.4		262.4
Asset Retirement Obligation Costs [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0.2		(1.6)		2.3
Development costs	171.9		173.3		49.1
Total Costs	172.1		171.7		51.4
Asset Retirement Obligation Costs [Member] | United States [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0		(1.7)		2.0
Development costs	70.1		37.9		15.8
Total Costs	70.1		36.2		17.8
Asset Retirement Obligation Costs [Member] | Canada [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0.2		0.1		0.3
Development costs	5.9		80.7		20.1
Total Costs	6.1		80.8		20.4
Asset Retirement Obligation Costs [Member] | Malaysia [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0		0		0
Development costs	95.9		48.6		0.3
Total Costs	95.9		48.6		0.3
Asset Retirement Obligation Costs [Member] | United Kingdom [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0		0		0
Development costs	0		(11.5)		10.8
Total Costs	0		(11.5)		10.8
Asset Retirement Obligation Costs [Member] | Republic of the Congo [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0		0		0
Development costs	0		17.6		2.1
Total Costs	0		17.6		2.1
Asset Retirement Obligation Costs [Member] | Other Regions [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Exploration costs	0		0		0
Development costs	0		0		0
Total Costs	$ 0		$ 0		$ 0

[1] Includes non-cash asset retirement costs as follows: 2013 Exploration costs $ 0.0 0.2 0.0 0.0 0.0 0.0 0.2 Development costs 70.1 5.9 95.9 0.0 0.0 0.0 171.9 $ 70.1 6.1 95.9 0.0 0.0 0.0 172.1 2012 Exploration costs $ (1.7 ) 0.1 0.0 0.0 0.0 0.0 (1.6 ) Development costs 37.9 80.7 48.6 (11.5 ) 17.6 0.0 173.3 $ 36.2 80.8 48.6 (11.5 ) 17.6 0.0 171.7 2011 Exploration costs $ 2.0 0.3 0.0 0.0 0.0 0.0 2.3 Development costs 15.8 20.1 0.3 10.8 2.1 0.0 49.1 $ 17.8 20.4 0.3 10.8 2.1 0.0 51.4

[2] Includes property cost associated with non-cash capital lease of $358.0 million at the Kakap field.

[3] The Company has accounted for U.K. operations as discontinued operations due to the sale of these operations in the first half of 2013.