Segment Reporting Information by Business Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Segment Reporting Disclosure [Line Items]
Total Assets	$ 17,551,138				$ 17,509,484
External Revenues	1,286,400		1,290,938	[1]
Income (Loss)	155,253		360,599	[1]
Corporate, Non-Segment [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	1,147,200
External Revenues	10,400		(8,100)	[1]
Income (Loss)	(41,300)		(49,200)	[1]
Exploration and production [Member] | Operating Segments [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	15,143,900	[2]
External Revenues	1,276,000	[2]	1,299,000	[1],[2]
Income (Loss)	210,600	[2]	231,900	[1],[2]
Exploration and production [Member] | Operating Segments [Member] | United States [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	4,967,800	[2]
External Revenues	485,500	[2]	408,900	[1],[2]
Income (Loss)	103,100	[2]	93,800	[1],[2]
Exploration and production [Member] | Operating Segments [Member] | Canada [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	3,957,100	[2]
External Revenues	297,700	[2]	260,800	[1],[2]
Income (Loss)	67,600	[2]	13,300	[1],[2]
Exploration and production [Member] | Operating Segments [Member] | Malaysia [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	6,076,100	[2]
External Revenues	492,800	[2]	560,000	[1],[2]
Income (Loss)	162,300	[2]	205,200	[1],[2]
Exploration and production [Member] | Operating Segments [Member] | Other Regions [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	142,900	[2]
External Revenues	0	[2]	69,300	[1],[2]
Income (Loss)	(122,400)	[2]	(80,400)	[1],[2]
Continuing Operations [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	16,291,100
External Revenues	1,286,400		1,290,900	[1]
Income (Loss)	169,300		182,700	[1]
Discontinued Operations [Member]
Segment Reporting Disclosure [Line Items]
Total Assets	1,260,000
External Revenues	0		0	[1]
Income (Loss)	$ (14,000)		$ 177,900	[1]

[1] Reclassified to conform to current presentation.

[2] Additional details about results of oil and gas operations are presented in the tables on page 21.