Property, Plant and Equipment - Components of Property, Plant and Equipment (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Pipeline Equipment [Member]
Property, Plant and Equipment [Line Items]
Accumulated DD&A	$ 1,620	$ 1,360
Offshore Drilling Equipment [Member]
Property, Plant and Equipment [Line Items]
Accumulated DD&A	4,159	3,727
Other [Member]
Property, Plant and Equipment [Line Items]
Accumulated DD&A	$ 730	$ 778