Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Marketable Debt and Equity Securities
Fair Value	$ 3,188.4	$ 2,111.1
Gross Unrealized Gains	1.7	0.7
Gross Unrealized Losses	(1.8)	(2.4)
Amortized Cost	3,188.5	2,112.8
Corporate debt securities Current
Marketable Debt and Equity Securities
Fair Value	375.9	370.4
Gross Unrealized Gains	0.1	0.0
Gross Unrealized Losses	(0.1)	(0.2)
Amortized Cost	375.9	370.6
Corporate debt securities Non-current
Marketable Debt and Equity Securities
Fair Value	822.2	692.6
Gross Unrealized Gains	0.4	0.2
Gross Unrealized Losses	(1.2)	(1.5)
Amortized Cost	823.0	693.9
Government securities Current
Marketable Debt and Equity Securities
Fair Value	710.5	269.9
Gross Unrealized Gains	0.1	0.0
Gross Unrealized Losses	(0.1)	(0.1)
Amortized Cost	710.5	270.0
Government securities Non-current
Marketable Debt and Equity Securities
Fair Value	989.8	579.9
Gross Unrealized Gains	0.9	0.3
Gross Unrealized Losses	(0.1)	(0.4)
Amortized Cost	989.0	580.0
Mortgage and other asset backed securities Current
Marketable Debt and Equity Securities
Fair Value	0.2	0.2
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Amortized Cost	0.2	0.2
Mortgage and other asset backed securities Non-current
Marketable Debt and Equity Securities
Fair Value	289.8	198.1
Gross Unrealized Gains	0.2	0.2
Gross Unrealized Losses	(0.3)	(0.2)
Amortized Cost	289.9	198.1
Marketable equity securities
Marketable Debt and Equity Securities
Fair Value	6.8	6.9
Gross Unrealized Gains	1.1	1.2
Gross Unrealized Losses	0.0	(0.2)
Amortized Cost	$ 5.7	$ 5.9

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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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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