Segment Information - Sales Revenues by Geographic Area Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue from External Customer [Line Items]
Sales revenues	$ 13,307	$ 13,882	$ 10,842
United States [Member]
Revenue from External Customer [Line Items]
Sales revenues	9,911	10,477	8,806
Algeria [Member]
Revenue from External Customer [Line Items]
Sales revenues	2,182	2,258	1,582
Other International [Member]
Revenue from External Customer [Line Items]
Sales revenues	$ 1,214	$ 1,147	$ 454

Amount of revenue from external customers for the reportable segment. Such disclosure is presented if the amount is: (a) included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration