Short-term Investments (Short-term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Trading investment securities	$ 25	$ 0
Available-for-sale investment securities	2,264	2,015
Held-to-maturity investment securities	40	0
Time deposits	806	809
Short-term Investments, Total	3,135	2,824
U.S. Treasury And Agency Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale investment securities	602	527
Corporate And Other Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale investment securities	405	361
Commercial Paper and Certificates of Deposit [Member]
Schedule of Investments [Line Items]
Available-for-sale investment securities	911	754
Held-to-maturity investment securities	40	0
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale investment securities	231	230
Municipal Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale investment securities	115	121
Mutual Fund [Member]
Schedule of Investments [Line Items]
Trading investment securities	25	0
Available-for-sale investment securities	$ 0	$ 22

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 25
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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle.

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Amount of other investments not classified as trading, available-for-sale or held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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Fair value of investments in trading equity securities and other forms of trading securities that provide ownership interests.

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