Capitalized Exploratory Well Costs - Additional Information (Detail) $ in Millions	1 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013 Well	Jun. 30, 2015 USD ($) Well	Dec. 31, 2014 Well
Capitalized Costs Of Unproved Properties Excluded From Amortization [Line Items]
Exploratory dry hole costs which were incurred and subsequently expensed | $		$ 56
Capitalized exploratory well costs that have been capitalized for period greater than one year | $		$ 1,247
Block WA-390-P, Offshore Western Australia [Member]
Capitalized Costs Of Unproved Properties Excluded From Amortization [Line Items]
Capitalized well costs		70.00%
Offshore Ghana [Member]
Capitalized Costs Of Unproved Properties Excluded From Amortization [Line Items]
Capitalized well costs		30.00%
Number of consecutive successful exploration wells		7
Number of wells appraisal drilling plans	7
Number of wells appraisal drilling plans approved		4
Number of wells appraisal drilling plans in process		3
Number of appraisal wells completed			3