Marketable Securities (current and non-current) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Marketable securities classification
Current marketable securities	$ 118	$ 1,439
Non-current marketable securities	9	15
Total marketable securities	127	1,454
U.S. government agency securities
Marketable securities classification
Current marketable securities		108
Foreign government agency securities
Marketable securities classification
Current marketable securities	10	95
Corporate debt securities
Marketable securities classification
Current marketable securities	10	619
Commercial paper
Marketable securities classification
Current marketable securities	12
Certificates of deposit/time deposits
Marketable securities classification
Current marketable securities	26	41
U.S. treasury securities
Marketable securities classification
Current marketable securities		38
U.S. municipal securities
Marketable securities classification
Current marketable securities	3
Non-current marketable securities	9	15
Asset-backed securities
Marketable securities classification
Current marketable securities	57	538
Asset-backed securities Automobile loan related
Marketable securities classification
Current marketable securities	26	282
Asset-backed securities Credit card related
Marketable securities classification
Current marketable securities	10	162
Asset-backed securities Equipment lease related
Marketable securities classification
Current marketable securities	2	48
Asset-backed securities Other asset-backed securities
Marketable securities classification
Current marketable securities	$ 19	$ 46

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=51813488&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
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-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
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Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Available-for-Sale Securities
-URI http://asc.fasb.org/extlink&oid=6505594

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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