Inventories (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Inventories [Abstract]
Percentage of inventories valued on LIFO basis	35.00%	35.00%
Total inventory valued at average cost basis	$ 801	$ 742
Recognition of income caused by partial liquidations of the lower cost LIFO inventory base, gross	2	27	175
Recognition of income caused by partial liquidations of the lower cost LIFO inventory base, after tax	$ 1	$ 17	$ 114

The amount of weighted average cost inventory present at the reporting date when inventory is valued using different valuation methods.

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 3

-Section A

-Paragraph 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant