Available-For-Sale Investments (Summary Of Fair Value Of Available-For-Sale Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total Short-Term Investments [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Amortized cost	$ 1,153	$ 1,156
Fair value	1,156	1,164
Total Long-Term Investments [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Amortized cost	51	57
Fair value	40	35
U.S. Government And Agencies [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Amortized cost	1,153	1,150
Fair value	1,156	1,155
Other Debt Securities [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Amortized cost		6
Fair value		9
Asset-Backed Securities [Member]
Schedule Of Available-For-Sale Securities [Line Items]
Amortized cost	51	57
Fair value	$ 40	$ 35

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 9: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 10: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details