Property, Plant and Equipment - Exploratory Drilling Costs Capitalized (Detail) $ in Millions	Dec. 31, 2015 USD ($)
Projects With Exploratory Well Costs Capitalized For More Than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year	$ 1,053
Year 2014
Projects With Exploratory Well Costs Capitalized For More Than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year	79
Year 2013
Projects With Exploratory Well Costs Capitalized For More Than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year	43
Year 2012
Projects With Exploratory Well Costs Capitalized For More Than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year	336
Year 2011
Projects With Exploratory Well Costs Capitalized For More Than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year	207
Year 2010 and prior
Projects With Exploratory Well Costs Capitalized For More Than One Year [Line Items]
Capitalized exploratory well costs that have been capitalized for period greater than one year	$ 388