Property, Plant and Equipment - Capitalized Exploratory Well Costs - Additional Information (Detail) $ in Millions	12 Months Ended			24 Months Ended
	Dec. 31, 2015 USD ($) Well	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) Well
Capitalized Exploratory Well Costs [Line Items]
Exploratory dry hole costs which were incurred and subsequently expensed | $	$ 54	$ 66	$ 77
Capitalized exploratory well costs that have been capitalized for period greater than one year | $	$ 1,053			$ 1,053
Block WA-390-P, Offshore Western Australia
Capitalized Exploratory Well Costs [Line Items]
Capitalized well costs percentage	75.00%			75.00%
Offshore Ghana
Capitalized Exploratory Well Costs [Line Items]
Capitalized well costs percentage	25.00%			25.00%
Appraisal plans for this number of wells submitted to the Ghanaian government	7			7
This number of appraisal wells was approved by the Ghanaian government	5			5
This number of appraisal wells is pending approval by the Ghanaian government	2			2
This number of approved appraisal wells is completed				3