Cash, Cash Equivalents and Marketable Securities Available-for-Sale (Amortized Cost, Gross Unrealized Gain/Loss, and Estimated Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Cash and cash equivalents
Money market funds	$ 2,251us-gaap_MoneyMarketFundsAtCarryingValue	$ 1,697us-gaap_MoneyMarketFundsAtCarryingValue
Available-for-sale securities by major security type and class of security
Amortized Cost	2,712.1	2,239.0
Gross Unrealized Gain	718.3	221.9
Gross Unrealized Loss	(5.3)	(8.3)
Estimated Fair Value	3,425.1	2,452.6
U.S. Treasury securities
Available-for-sale securities by major security type and class of security
Amortized Cost	1,044.7	795.2
Gross Unrealized Gain	0.3	0.3
Gross Unrealized Loss	(0.8)	(0.4)
Estimated Fair Value	1,044.2	795.1
U.S. government-sponsored agency securities
Available-for-sale securities by major security type and class of security
Amortized Cost	145.1	208.9
Gross Unrealized Gain	0.1	0.2
Gross Unrealized Loss	(0.1)	(0.2)
Estimated Fair Value	145.1	208.9
U.S. government-sponsored agency MBS
Available-for-sale securities by major security type and class of security
Amortized Cost	531.1	450.8
Gross Unrealized Gain	1.0	0.1
Gross Unrealized Loss	(2.7)	(6.9)
Estimated Fair Value	529.4	444.0
Non-U.S. government, agency and supranational securities
Available-for-sale securities by major security type and class of security
Amortized Cost	32.4	10.4
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(0.1)	0
Estimated Fair Value	32.3	10.4
Corporate debt – global
Available-for-sale securities by major security type and class of security
Amortized Cost	446.3	379.2
Gross Unrealized Gain	0.6	1.1
Gross Unrealized Loss	(1.2)	(0.6)
Estimated Fair Value	445.7	379.7
Asset backed securities
Available-for-sale securities by major security type and class of security
Amortized Cost	177.3	181.6
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(0.2)	(0.2)
Estimated Fair Value	177.1	181.4
Marketable equity securities
Available-for-sale securities by major security type and class of security
Amortized Cost	335.2	212.9
Gross Unrealized Gain	716.3	220.2
Gross Unrealized Loss	(0.2)	0
Estimated Fair Value	$ 1,051.3	$ 433.1

Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax

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- Definition

Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax

+ References

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- 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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

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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.

+ References

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)

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

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