Supplemental Oil and Gas Disclosures - Revenue and Direct Cost Information Relating to Company's Oil and Gas Exploration and Production Activities (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) $ / Boe	Dec. 31, 2014 USD ($) $ / Boe	Dec. 31, 2013 USD ($) $ / Boe
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	$ 6,383	$ 12,691	$ 14,771
Depreciation, depletion, and amortization
Recurring	3,531	4,388	4,533
Additional	25,517	5,001	995
Asset retirement obligation accretion	145	154	211
Lease operating expenses	1,854	2,238	2,650
Gathering and transportation	211	273	288
Production taxes	259	546	746
Income tax	(8,849)	236	2,315
Oil and gas properties production expense	22,668	12,836	11,738
Results of operation	$ (16,285)	$ (145)	$ 3,033
Amortization rate per boe | $ / Boe	18.08	20.36	18.77
United States [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	$ 2,637	$ 5,744	$ 6,902
Depreciation, depletion, and amortization
Recurring	1,419	2,056	2,227
Additional	19,537	4,412	552
Asset retirement obligation accretion	28	43	94
Lease operating expenses	739	921	1,320
Gathering and transportation	68	93	84
Production taxes	178	342	324
Income tax	(6,863)	(754)	817
Oil and gas properties production expense	15,106	7,113	5,418
Results of operation	$ (12,469)	$ (1,369)	$ 1,484
Amortization rate per boe | $ / Boe	15.49	19.35	18.39
Canada [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	$ 498	$ 1,092	$ 1,224
Depreciation, depletion, and amortization
Recurring	262	343	426
Additional	3,667
Asset retirement obligation accretion	43	39	49
Lease operating expenses	244	384	459
Gathering and transportation	89	123	155
Production taxes	23	27	40
Income tax	(1,000)	44	24
Oil and gas properties production expense	3,328	960	1,153
Results of operation	$ (2,830)	$ 132	$ 71
Amortization rate per boe | $ / Boe	10.61	12.11	10.89
Egypt [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	$ 1,968	$ 3,539	$ 3,917
Depreciation, depletion, and amortization
Recurring	1,128	1,014	881
Additional	281
Lease operating expenses	522	499	471
Gathering and transportation	45	40	42
Income tax	(4)	914	1,161
Oil and gas properties production expense	1,972	2,467	2,555
Results of operation	$ (4)	$ 1,072	$ 1,362
Amortization rate per boe | $ / Boe	21.29	18.48	16.21
North Sea [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	$ 1,280	$ 2,316	$ 2,728
Depreciation, depletion, and amortization
Recurring	722	975	999
Additional	2,032	589	367
Asset retirement obligation accretion	74	72	68
Lease operating expenses	349	434	400
Gathering and transportation	9	17	7
Production taxes	58	177	382
Income tax	(982)	32	313
Oil and gas properties production expense	2,262	2,296	2,536
Results of operation	$ (982)	$ 20	$ 192
Amortization rate per boe | $ / Boe	27.77	37.41	37.25
Other International [Member]
Depreciation, depletion, and amortization
Additional			$ 76
Oil and gas properties production expense			76
Results of operation			$ (76)