Marketable Securities And Cash Equivalents (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2013 security
Investments, Debt and Equity Securities [Abstract]
Unrealized losses that arose within the last 12 months	$ 2	$ 2
Number of available-for-sale equity securities with unrealized losses (in securities)		1
Market value of the investments that have been in an unrealized loss position for less than 12 months	5	5
Other than temporary impairment losses recognized in earnings	$ 11

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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