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Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Assets: |  |  |
Cash equivalents | $ 2,541.1 | $ 705.5 |
Marketable equity securities | 337.5 | 615.4 |
Derivative contracts | 43.8 | 66.9 |
Plan assets for deferred compensation | 27.7 | 25.4 |
Total | 5,920.4 | 5,102.5 |
Liabilities: |  |  |
Derivative contracts | 8.3 | 24.6 |
Contingent consideration obligations | 346.1 | 409.8 | $ 523.6
Total | 354.4 | 434.4 |
Corporate debt securities |  |  |
Assets: |  |  |
Marketable debt securities | 1,695.1 | 2,459.2 |
Government securities |  |  |
Assets: |  |  |
Marketable debt securities | 1,013.9 | 969.6 |
Mortgage and other asset backed securities |  |  |
Assets: |  |  |
Marketable debt securities | 261.3 | 260.5 |
Quoted Prices in Active Markets (Level 1) |  |  |
Assets: |  |  |
Cash equivalents | 0.0 | 0.0 |
Marketable equity securities | 7.9 | 51.7 |
Derivative contracts | 0.0 | 0.0 |
Plan assets for deferred compensation | 0.0 | 0.0 |
Total | 7.9 | 51.7 |
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) | Corporate debt securities |  |  |
Assets: |  |  |
Marketable debt securities | 0.0 | 0.0 |
Quoted Prices in Active Markets (Level 1) | Government securities |  |  |
Assets: |  |  |
Marketable debt securities | 0.0 | 0.0 |
Quoted Prices in Active Markets (Level 1) | Mortgage and other asset backed securities |  |  |
Assets: |  |  |
Marketable debt securities | 0.0 | 0.0 |
Significant Other Observable Inputs (Level 2) |  |  |
Assets: |  |  |
Cash equivalents | 2,541.1 | 705.5 |
Marketable equity securities | 329.6 | 563.7 |
Derivative contracts | 43.8 | 66.9 |
Plan assets for deferred compensation | 27.7 | 25.4 |
Total | 5,912.5 | 5,050.8 |
Liabilities: |  |  |
Derivative contracts | 8.3 | 24.6 |
Contingent consideration obligations | 0.0 | 0.0 |
Total | 8.3 | 24.6 |
Significant Other Observable Inputs (Level 2) | Corporate debt securities |  |  |
Assets: |  |  |
Marketable debt securities | 1,695.1 | 2,459.2 |
Significant Other Observable Inputs (Level 2) | Government securities |  |  |
Assets: |  |  |
Marketable debt securities | 1,013.9 | 969.6 |
Significant Other Observable Inputs (Level 2) | Mortgage and other asset backed securities |  |  |
Assets: |  |  |
Marketable debt securities | 261.3 | 260.5 |
Significant Unobservable Inputs (Level 3) |  |  |
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 | 346.1 | 409.8 |
Total | 346.1 | 409.8 |
Significant Unobservable Inputs (Level 3) | Corporate debt securities |  |  |
Assets: |  |  |
Marketable debt securities | 0.0 | 0.0 |
Significant Unobservable Inputs (Level 3) | Government securities |  |  |
Assets: |  |  |
Marketable debt securities | 0.0 | 0.0 |
Significant Unobservable Inputs (Level 3) | Mortgage and other asset backed securities |  |  |
Assets: |  |  |
Marketable debt securities | $ 0.0 | $ 0.0 |

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