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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

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