Investment in Equity Affiliate - Schedule of Assets and Liabilities (Detail) (Petrodelta, S.A. [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Petrodelta, S.A. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Current assets	$ 1,906,595	$ 1,425,115
Property and equipment	717,449	538,351
Other assets	181,116	70,468
Current liabilities	1,652,806	1,180,559
Other liabilities	136,298	93,101
Net equity	$ 1,016,056	$ 760,274