Segment and Geographic Area Information - Schedule of Geographic Information for Long-Lived Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 18,947	$ 19,282
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	4,621	4,439
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	4,318	4,844
Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	3,548	3,390
Iceland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	1,571	1,615
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	1,399	1,447
Norway [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	898	894
Russia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	494	531
Spain [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	445	451
Jamaica [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	414	417
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	395	424
Other Geographical Regions [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 844	$ 830