Aging of Capitalized Exploratory Well Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Well Project	Mar. 31, 2013 Well Project	Dec. 31, 2013	Dec. 31, 2012
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	$ 395,949	$ 444,228	$ 393,030	$ 445,697
No. of Wells	32	41
No. of Projects	9	11
Zero to one year [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	32,192	56,324
No. of Wells	2	6
No. of Projects	1	3
One to two years [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	56,702	40,721
No. of Wells	6	3
No. of Projects	1	1
Two to three years [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	31,224	79,446
No. of Wells	2	8
No. of Projects	0	2
Three years or more [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	$ 275,831	$ 267,737
No. of Wells	22	24
No. of Projects	7	5