Financial Instruments (Details 1) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Marketable Debt and Equity Securities
Fair Value	$ 4,781.4	$ 5,398.0
Gross Unrealized Gains	4.3	2.9
Gross Unrealized Losses	(8.9)	(11.2)
Amortized Cost	4,786.0	5,406.3
Corporate debt securities Current
Marketable Debt and Equity Securities
Fair Value	1,288.5	1,408.6
Gross Unrealized Gains	0.1	0.2
Gross Unrealized Losses	(0.8)	(0.6)
Amortized Cost	1,289.2	1,409.0
Corporate debt securities Non-current
Marketable Debt and Equity Securities
Fair Value	1,212.2	1,255.2
Gross Unrealized Gains	2.1	1.2
Gross Unrealized Losses	(3.3)	(4.7)
Amortized Cost	1,213.4	1,258.7
Government securities Current
Marketable Debt and Equity Securities
Fair Value	664.4	1,156.0
Gross Unrealized Gains	0.2	0.2
Gross Unrealized Losses	(0.4)	(0.3)
Amortized Cost	664.6	1,156.1
Government securities Non-current
Marketable Debt and Equity Securities
Fair Value	1,073.8	1,016.5
Gross Unrealized Gains	0.8	0.5
Gross Unrealized Losses	(3.0)	(3.4)
Amortized Cost	1,076.0	1,019.4
Mortgage and other asset backed securities Current
Marketable Debt and Equity Securities
Fair Value	3.3	4.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Amortized Cost	3.3	4.0
Mortgage and other asset backed securities Non-current
Marketable Debt and Equity Securities
Fair Value	539.2	557.7
Gross Unrealized Gains	1.1	0.8
Gross Unrealized Losses	(1.4)	(2.2)
Amortized Cost	539.5	559.1
Marketable equity securities
Marketable Debt and Equity Securities
Fair Value	18.7	24.9
Gross Unrealized Gains	0.0	0.7
Gross Unrealized Losses	(14.9)	(9.3)
Amortized Cost	$ 33.6	$ 33.5

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=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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