Property, Plant and Equipment - Components of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Construction in process	$ 317	$ 458
Property, plant and equipment	15,511	15,427
Pipeline Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	8,238	7,857
Offshore Drilling Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	5,144	5,226
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,812	$ 1,886