Cash, Cash Equivalents and Marketable Securities Available-for-Sale (Amortized Cost, Gross Unrealized Gain/Loss, and Estimated Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Cash and cash equivalents
Money market funds	$ 1,413.0	$ 2,251.0
Available-for-sale securities by major security type and class of security
Amortized Cost	1,249.6	2,712.1
Gross Unrealized Gain	468.2	718.3
Gross Unrealized Loss	(46.2)	(5.3)
Estimated Fair Value	1,671.6	3,425.1
U.S. Treasury securities
Available-for-sale securities by major security type and class of security
Amortized Cost	153.0	1,044.7
Gross Unrealized Gain	0.0	0.3
Gross Unrealized Loss	(0.4)	(0.8)
Estimated Fair Value	152.6	1,044.2
U.S. government-sponsored agency securities
Available-for-sale securities by major security type and class of security
Amortized Cost		145.1
Gross Unrealized Gain		0.1
Gross Unrealized Loss		(0.1)
Estimated Fair Value		145.1
U.S. government-sponsored agency MBS
Available-for-sale securities by major security type and class of security
Amortized Cost	29.8	531.1
Gross Unrealized Gain	0.1	1.0
Gross Unrealized Loss	(0.4)	(2.7)
Estimated Fair Value	29.5	529.4
Non-U.S. government, agency and supranational securities
Available-for-sale securities by major security type and class of security
Amortized Cost		32.4
Gross Unrealized Gain		0.0
Gross Unrealized Loss		(0.1)
Estimated Fair Value		32.3
Corporate debt – global
Available-for-sale securities by major security type and class of security
Amortized Cost	219.7	446.3
Gross Unrealized Gain	0.0	0.6
Gross Unrealized Loss	(1.6)	(1.2)
Estimated Fair Value	218.1	445.7
Asset backed securities
Available-for-sale securities by major security type and class of security
Amortized Cost	35.6	177.3
Gross Unrealized Gain	0.0	0.0
Gross Unrealized Loss	(0.1)	(0.2)
Estimated Fair Value	35.5	177.1
Marketable equity securities
Available-for-sale securities by major security type and class of security
Amortized Cost	811.5	335.2
Gross Unrealized Gain	468.1	716.3
Gross Unrealized Loss	(43.7)	(0.2)
Estimated Fair Value	$ 1,235.9	$ 1,051.3

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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)
-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 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26626-111562

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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