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Fair Value Measurements (Details) - USD ($) $ in Millions | Mar. 31, 2017 | Dec. 31, 2016 | Mar. 31, 2016 | Dec. 31, 2015
--- | --- | --- | --- | ---
Assets: |  |  |  |
Marketable debt securities | $ 4,781.4 | $ 5,398.0 |  |
Fair Value, Measurements, Recurring |  |  |  |
Assets: |  |  |  |
Cash equivalents | 645.1 | 2,039.6 |  |
Marketable equity securities | 18.7 | 24.9 |  |
Derivative contracts | 44.5 | 61.0 |  |
Plan assets for deferred compensation | 31.0 | 34.5 |  |
Total | 5,520.7 | 7,558.0 |  |
Liabilities: |  |  |  |
Derivative contracts | 13.6 | 13.6 |  |
Contingent consideration obligations | 470.9 | 467.6 | $ 508.3 | $ 506.0
Total | 484.5 | 481.2 |  |
Fair Value, Measurements, Recurring | Corporate debt securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 2,500.7 | 2,663.8 |  |
Fair Value, Measurements, Recurring | Government securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 1,738.2 | 2,172.5 |  |
Fair Value, Measurements, Recurring | Mortgage and other asset backed securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 542.5 | 561.7 |  |
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring |  |  |  |
Assets: |  |  |  |
Cash equivalents | 0.0 | 0.0 |  |
Marketable equity securities | 18.7 | 24.9 |  |
Derivative contracts | 0.0 | 0.0 |  |
Plan assets for deferred compensation | 0.0 | 0.0 |  |
Total | 18.7 | 24.9 |  |
Liabilities: |  |  |  |
Derivative contracts | 0.0 | 0.0 |  |
Contingent consideration obligations | 0.0 | 0.0 |  |
Total | 0.0 | 0.0 |  |
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring | Corporate debt securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 0.0 | 0.0 |  |
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring | Government securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 0.0 | 0.0 |  |
Quoted Prices in Active Markets, Level 1 | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 0.0 | 0.0 |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring |  |  |  |
Assets: |  |  |  |
Cash equivalents | 645.1 | 2,039.6 |  |
Marketable equity securities | 0.0 | 0.0 |  |
Derivative contracts | 44.5 | 61.0 |  |
Plan assets for deferred compensation | 31.0 | 34.5 |  |
Total | 5,502.0 | 7,533.1 |  |
Liabilities: |  |  |  |
Derivative contracts | 13.6 | 13.6 |  |
Contingent consideration obligations | 0.0 | 0.0 |  |
Total | 13.6 | 13.6 |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate debt securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 2,500.7 | 2,663.8 |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Government securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 1,738.2 | 2,172.5 |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 542.5 | 561.7 |  |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring |  |  |  |
Assets: |  |  |  |
Cash equivalents | 0.0 | 0.0 |  |
Marketable equity securities | 0.0 | 0.0 |  |
Derivative contracts | 0.0 | 0.0 |  |
Plan assets for deferred compensation | 0.0 | 0.0 |  |
Total | 0.0 | 0.0 |  |
Liabilities: |  |  |  |
Derivative contracts | 0.0 | 0.0 |  |
Contingent consideration obligations | 470.9 | 467.6 |  |
Total | 470.9 | 467.6 |  |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Corporate debt securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 0.0 | 0.0 |  |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Government securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | 0.0 | 0.0 |  |
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities |  |  |  |
Assets: |  |  |  |
Marketable debt securities | $ 0.0 | $ 0.0 |  |

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