Schedule of Interest Income and Interest Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Amounts Related To Interest [Line Items]
Interest expense	$ 197	[1]	$ 144	[1]	$ 559	[1]	$ 444	[1]
Interest income	34	[1]	14	[1]	56	[1]	41	[1]
Capitalized interest costs	$ 10		$ 6		$ 29		$ 14

[1] (a)Interest expense and interest income exclude approximately $15 million and $35 million for the three months and nine months ended September 30, 2012, respectively, and $13 million and $39 million for the three months and nine months ended September 30, 2011, respectively, related to investments in and borrowings from variable interest entities for which the Company has a legal right of offset (see Note 12).