Investment in Equity Affiliate - Summary of Financial Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Adjustments to increase (decrease) net income under IFRS
Earnings from equity affiliate included in income income	$ (10,242)	$ 25,747	$ 7,602	$ 49,471	$ 7,745	$ 20,299	$ 22,829	$ 16,896	$ 72,578	$ 67,769	$ 73,451
Petrodelta, S.A. [Member]
Revenues:
Oil sales									1,326,093	1,263,264	1,122,191
Gas sales									4,000	3,350	3,497
Royalty									(440,963)	(423,069)	(374,135)
Revenue, total									889,130	843,545	751,553
EXPENSES:
Operating expenses									151,661	121,023	77,236
Workovers									29,168	17,302	28,508
Depletion, depreciation and amortization									87,203	86,004	58,376
General and administrative									26,345	31,753	11,297
Windfall profits tax									234,453	291,355	237,632
Windfall profits credit									(55,168)	0	0
Total expenses									473,662	547,437	413,049
Income from operations									415,468	296,108	338,504
Gain on exchange rate									169,582	0	0
Investment earnings and other									15	13	610
Interest expense									(21,728)	(7,017)	(10,699)
Income before income tax									563,337	289,104	328,415
Current income tax expense									325,217	127,080	190,577
Deferred income tax expense (benefit)									(17,662)	76,030	(94,622)
Net income under IFRS									255,782	85,994	232,460
Adjustments to increase (decrease) net income under IFRS
Deferred income tax (expense) benefit									9,080	78,968	(49,545)
Depletion expense									(20,352)	7,282	1,908
Reversal of windfall profits tax credit									(55,168)	0	0
Sports law over accrual									1,313	2,536	0
Net income under U.S. GAAP									190,655	174,780	184,823
Equity interest in equity affiliate									40.00%	40.00%	40.00%
Income before amortization of excess basis in equity affiliate									76,262	69,912	73,929
Amortization of excess basis in equity affiliate									(3,684)	(2,143)	(1,863)
Earnings from equity affiliate included in income income									$ 72,578	$ 67,769	$ 72,066