Supplemental Oil and Gas Disclosures (Unaudited) - Oil and Gas Reserve Information (Detail)	12 Months Ended
	Dec. 31, 2016 MBoe MMcf MBbls	Dec. 31, 2015 MBoe MMcf MBbls	Dec. 31, 2014 MBoe MMcf MBbls	Dec. 31, 2013 MBoe MMcf MBbls
Reserve Quantities [Line Items]
Proved developed reserves	1,173,635	1,331,397	1,651,291	1,832,936
Proved undeveloped reserves	137,616	232,336	744,979	813,480
Beginning balance	1,563,733	2,396,270	2,646,416
Extensions, discoveries and other additions	103,204	117,405	313,095
Purchase of minerals in-place	1,580	6,860	21,712
Revisions of previous estimates	(159,341)	(365,135)	14,150
Production	(190,942)	(206,840)	(241,577)
Sale of properties	(6,983)	(384,827)	(357,526)
Ending balance	1,311,251	1,563,733	2,396,270
Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves	252,630	275,033	236,256	222,880
Proved undeveloped reserves	27,336	26,929	43,446	48,028
Beginning balance	301,962	279,702	270,908
Extensions, discoveries and other additions	23,674	40,464	60,877
Revisions of previous estimates	16,599	37,825	5,522
Production	(62,269)	(56,029)	(57,605)
Ending balance	279,966	301,962	279,702
United States [Member]
Reserve Quantities [Line Items]
Proved developed reserves	656,087	726,424	897,422	976,795
Proved undeveloped reserves	76,950	120,210	336,670	370,566
Beginning balance	846,634	1,234,092	1,347,361
Extensions, discoveries and other additions	56,458	26,488	138,413
Purchase of minerals in-place	24		21,712
Revisions of previous estimates	(87,954)	(322,123)	11,662
Production	(81,994)	(91,591)	(106,225)
Sale of properties	(131)	(232)	(178,831)
Ending balance	733,037	846,634	1,234,092
Canada [Member]
Reserve Quantities [Line Items]
Proved developed reserves	157,662	209,647	258,848	322,362
Proved undeveloped reserves	17,931	70,300	155,028	139,509
Beginning balance	279,947	413,876	461,871
Extensions, discoveries and other additions	9,166	26,226	74,666
Purchase of minerals in-place		6,860
Revisions of previous estimates	(84,984)	(87,081)	(2,800)
Production	(21,684)	(24,706)	(28,313)
Sale of properties	(6,852)	(55,228)	(91,548)
Ending balance	175,593	279,947	413,876
Australia [Member]
Reserve Quantities [Line Items]
Proved developed reserves			136,707	126,948
Proved undeveloped reserves			186,534	199,240
Beginning balance	0	323,241	326,188
Extensions, discoveries and other additions			17,780
Revisions of previous estimates	0	12,549	(216)
Production	0	(8,503)	(20,511)
Sale of properties	0	(327,287)
Ending balance		0	323,241
North Sea [Member]
Reserve Quantities [Line Items]
Proved developed reserves	107,256	120,293	122,058	117,457
Proved undeveloped reserves	15,399	14,897	23,301	32,633
Beginning balance	135,190	145,359	150,090
Extensions, discoveries and other additions	13,906	24,227	21,354
Purchase of minerals in-place	1,556
Revisions of previous estimates	(3,002)	(6,305)	(18)
Production	(24,995)	(26,011)	(26,067)
Sale of properties	0	(2,080)
Ending balance	122,655	135,190	145,359
Argentina [Member]
Reserve Quantities [Line Items]
Proved developed reserves				66,494
Proved undeveloped reserves				23,504
Beginning balance			89,998
Extensions, discoveries and other additions			5
Revisions of previous estimates			0
Production			(2,856)
Sale of properties			(87,147)
Crude Oil and Condensate [Member]
Reserve Quantities [Line Items]
Proved developed reserves	582,317	665,063	784,770	794,795
Proved undeveloped reserves	59,965	127,996	289,499	336,690
Beginning balance	793,059	1,074,269	1,131,485
Extensions, discoveries and other additions	40,351	59,556	126,387
Purchase of minerals in-place	459	1,763	15,240
Revisions of previous estimates	(88,714)	(165,609)	4,693
Production	(100,744)	(108,491)	(118,412)
Sale of properties	(2,129)	(68,429)	(85,124)
Ending balance	642,282	793,059	1,074,269
Crude Oil and Condensate [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves	138,771	144,164	128,712	119,242
Proved undeveloped reserves	20,187	17,856	14,617	16,302
Beginning balance	162,020	143,329	135,544
Extensions, discoveries and other additions	17,599	24,524	38,074
Revisions of previous estimates	17,301	27,330	2,645
Production	(37,962)	(33,163)	(32,934)
Ending balance	158,958	162,020	143,329
Crude Oil and Condensate [Member] | United States [Member]
Reserve Quantities [Line Items]
Proved developed reserves	300,900	348,797	444,440	457,981
Proved undeveloped reserves	21,088	60,505	170,125	195,835
Beginning balance	409,302	614,565	653,816
Extensions, discoveries and other additions	9,614	13,903	57,011
Purchase of minerals in-place	21		15,240
Revisions of previous estimates	(58,882)	(173,907)	3,083
Production	(38,000)	(45,138)	(48,789)
Sale of properties	(67)	(121)	(65,796)
Ending balance	321,988	409,302	614,565
Crude Oil and Condensate [Member] | Canada [Member]
Reserve Quantities [Line Items]
Proved developed reserves	51,508	67,847	75,876	80,526
Proved undeveloped reserves	7,906	38,326	59,923	56,366
Beginning balance	106,173	135,799	136,892
Extensions, discoveries and other additions	3,372	4,550	9,657
Purchase of minerals in-place		1,763
Revisions of previous estimates	(43,282)	(27,966)	(812)
Production	(4,787)	(5,755)	(6,421)
Sale of properties	(2,062)	(2,218)	(3,517)
Ending balance	59,414	106,173	135,799
Crude Oil and Condensate [Member] | Australia [Member]
Reserve Quantities [Line Items]
Proved developed reserves			29,996	22,524
Proved undeveloped reserves			25,775	36,703
Beginning balance		55,771	59,227
Extensions, discoveries and other additions		0	4,254
Revisions of previous estimates		11,189	(216)
Production		(2,778)	(7,494)
Sale of properties		(64,182)
Ending balance			55,771
Crude Oil and Condensate [Member] | North Sea [Member]
Reserve Quantities [Line Items]
Proved developed reserves	91,138	104,255	105,746	100,327
Proved undeveloped reserves	10,784	11,309	19,059	29,253
Beginning balance	115,564	124,805	129,580
Extensions, discoveries and other additions	9,766	16,579	17,386
Purchase of minerals in-place	438
Revisions of previous estimates	(3,851)	(2,255)	(7)
Production	(19,995)	(21,657)	(22,154)
Sale of properties		(1,908)
Ending balance	101,922	115,564	124,805
Crude Oil and Condensate [Member] | Argentina [Member]
Reserve Quantities [Line Items]
Proved developed reserves				14,195
Proved undeveloped reserves				2,231
Beginning balance			16,426
Extensions, discoveries and other additions			5
Production			(620)
Sale of properties			(15,811)
Natural Gas Liquids [Member]
Reserve Quantities [Line Items]
Proved developed reserves	171,883	168,786	204,628	217,129
Proved undeveloped reserves	20,561	30,151	77,579	74,732
Beginning balance	198,937	282,207	291,861
Extensions, discoveries and other additions	11,872	8,074	50,500
Purchase of minerals in-place	7	976	2,916
Revisions of previous estimates	5,627	(69,178)	2,697
Production	(22,942)	(22,721)	(24,595)
Sale of properties	(1,057)	(421)	(41,172)
Ending balance	192,444	198,937	282,207
Natural Gas Liquids [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves	1,266	1,491	1,346
Proved undeveloped reserves	131	78	212
Beginning balance	1,569	1,558
Extensions, discoveries and other additions	208	144	1,820
Revisions of previous estimates	17	255	(11)
Production	(397)	(388)	(251)
Ending balance	1,397	1,569	1,558
Natural Gas Liquids [Member] | United States [Member]
Reserve Quantities [Line Items]
Proved developed reserves	155,124	150,265	183,565	184,485
Proved undeveloped reserves	17,311	24,939	69,828	63,538
Beginning balance	175,204	253,393	248,023
Extensions, discoveries and other additions	10,238	5,768	47,516
Purchase of minerals in-place	2		2,916
Revisions of previous estimates	6,824	(64,226)	2,594
Production	(19,824)	(19,684)	(21,464)
Sale of properties	(9)	(47)	(26,192)
Ending balance	172,435	175,204	253,393
Natural Gas Liquids [Member] | Canada [Member]
Reserve Quantities [Line Items]
Proved developed reserves	13,866	15,246	17,947	26,099
Proved undeveloped reserves	2,473	4,839	7,168	9,970
Beginning balance	20,085	25,115	36,069
Extensions, discoveries and other additions	755	1,473	1,163
Purchase of minerals in-place		976
Revisions of previous estimates	(1,355)	(4,886)	116
Production	(2,098)	(2,236)	(2,256)
Sale of properties	(1,048)	(357)	(9,977)
Ending balance	16,339	20,085	25,115
Natural Gas Liquids [Member] | North Sea [Member]
Reserve Quantities [Line Items]
Proved developed reserves	1,627	1,784	1,770	2,435
Proved undeveloped reserves	646	295	371	215
Beginning balance	2,079	2,141	2,650
Extensions, discoveries and other additions	671	689	1
Purchase of minerals in-place	5
Revisions of previous estimates	141	(321)	(2)
Production	(623)	(413)	(508)
Sale of properties		(17)
Ending balance	2,273	2,079	2,141
Natural Gas Liquids [Member] | Argentina [Member]
Reserve Quantities [Line Items]
Proved developed reserves				4,110
Proved undeveloped reserves				1,009
Beginning balance			5,119
Production			(116)
Sale of properties			(5,003)
Natural Gas [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf	2,516,610	2,985,290	3,971,360	4,926,064
Proved undeveloped reserves | MMcf	342,538	445,132	2,267,400	2,412,348
Beginning balance | MMcf	3,430,422	6,238,760	7,338,412
Extensions, discoveries and other additions | MMcf	305,883	298,649	817,253
Purchase of minerals in-place | MMcf	6,684	24,727	21,337
Revisions of previous estimates | MMcf	(457,524)	(782,083)	40,556
Production | MMcf	(403,533)	(453,772)	(591,420)
Sale of properties | MMcf	(22,784)	(1,895,859)	(1,387,378)
Ending balance | MMcf	2,859,148	3,430,422	6,238,760
Natural Gas [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf	675,559	776,263	637,187	621,825
Proved undeveloped reserves | MMcf	42,109	53,969	171,696	190,355
Beginning balance | MMcf	830,232	808,883	812,180
Extensions, discoveries and other additions | MMcf	35,202	94,777	125,899
Revisions of previous estimates | MMcf	(4,305)	61,442	17,326
Production | MMcf	(143,461)	(134,870)	(146,522)
Ending balance | MMcf	717,668	830,232	808,883
Natural Gas [Member] | United States [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf	1,200,379	1,364,174	1,616,504	2,005,966
Proved undeveloped reserves | MMcf	231,304	208,594	580,299	667,160
Beginning balance | MMcf	1,572,768	2,196,803	2,673,126
Extensions, discoveries and other additions | MMcf	219,633	40,901	203,318
Purchase of minerals in-place | MMcf	7		21,337
Revisions of previous estimates | MMcf	(215,378)	(503,939)	35,910
Production | MMcf	(145,019)	(160,614)	(215,829)
Sale of properties | MMcf	(328)	(383)	(521,059)
Ending balance | MMcf	1,431,683	1,572,768	2,196,803
Natural Gas [Member] | Canada [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf	553,724	759,321	990,145	1,294,420
Proved undeveloped reserves | MMcf	45,312	162,809	527,623	439,037
Beginning balance | MMcf	922,130	1,517,768	1,733,457
Extensions, discoveries and other additions | MMcf	30,234	121,216	383,077
Purchase of minerals in-place | MMcf		24,727
Revisions of previous estimates | MMcf	(242,080)	(325,375)	(12,626)
Production | MMcf	(88,792)	(100,289)	(117,816)
Sale of properties | MMcf	(22,456)	(315,917)	(468,324)
Ending balance | MMcf	599,036	922,130	1,517,768
Natural Gas [Member] | Australia [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf			640,265	626,543
Proved undeveloped reserves | MMcf			964,554	975,224
Beginning balance | MMcf		1,604,819	1,601,767
Extensions, discoveries and other additions | MMcf			81,156
Revisions of previous estimates | MMcf		8,162
Production | MMcf		(34,352)	(78,104)
Sale of properties | MMcf		(1,578,629)
Ending balance | MMcf			1,604,819
Natural Gas [Member] | North Sea [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf	86,948	85,532	87,259	88,177
Proved undeveloped reserves | MMcf	23,813	19,760	23,228	18,988
Beginning balance | MMcf	105,292	110,487	107,165
Extensions, discoveries and other additions | MMcf	20,814	41,755	23,803
Purchase of minerals in-place | MMcf	6,677
Revisions of previous estimates | MMcf	4,239	(22,373)	(54)
Production | MMcf	(26,261)	(23,647)	(20,427)
Sale of properties | MMcf		(930)
Ending balance | MMcf	110,761	105,292	110,487
Natural Gas [Member] | Argentina [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf				289,133
Proved undeveloped reserves | MMcf				121,584
Beginning balance | MMcf			410,717
Production | MMcf			(12,722)
Sale of properties | MMcf			(397,995)
Noncontrolling Interest [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves (Energy) | MBoe	93,322	101,000	93,000	90,000
Noncontrolling Interest [Member] | Crude Oil and Condensate [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves	52,986	54,007	47,776	45,181
Noncontrolling Interest [Member] | Natural Gas Liquids [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves	466	523	519
Noncontrolling Interest [Member] | Natural Gas [Member] | Egypt [Member]
Reserve Quantities [Line Items]
Proved developed reserves | MMcf	239,223	277	270	271