Marketable Securities (Contractual maturity) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Marketable securities by contractual maturity
Due in one year or less	$ 285
Due after one year through five years	1,915
Due after five years through ten years	20
Due after ten years	0
Total marketable securities	$ 2,220	$ 2,209

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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Amount of available-for-sale debt securities at fair value maturing in the next rolling twelve months following the latest balance sheet presented.

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Amount of available-for-sale debt securities at fair value maturing after the tenth rolling twelve months following the latest balance sheet presented.

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Amount of available-for-sale debt securities at fair value maturing in the sixth rolling twelve months through the tenth rolling twelve months following the latest balance sheet presented.

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Amount of available-for-sale debt securities at fair value maturing in the second rolling twelve months through the fifth rolling twelve months following the latest balance sheet presented.

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No definition available.

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