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Fair Value Measurements (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Jun. 30, 2021 | Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Dec. 31, 2019
--- | --- | --- | --- | --- | --- | ---
Assets: |  |  |  |  |  |
Marketable debt securities | $ 2,381.6 |  | $ 2,051.0 |  |  |
Fair Value, Measurements, Recurring |  |  |  |  |  |
Assets: |  |  |  |  |  |
Cash equivalents | 978.9 |  | 626.9 |  |  |
Marketable equity securities | 1,166.2 |  | 1,974.3 |  |  |
Derivative contracts | 80.0 |  | 20.5 |  |  |
Plan assets for deferred compensation | 33.7 |  | 28.2 |  |  |
Total | 4,640.4 |  | 4,700.9 |  |  |
Liabilities: |  |  |  |  |  |
Derivative contracts | 27.7 |  | 217.2 |  |  |
Contingent consideration obligations | 210.7 | $ 226.3 | 259.8 | $ 322.6 | $ 351.6 | $ 346.1
Total | 238.4 |  | 477.0 |  |  |
Fair Value, Measurements, Recurring | Corporate debt securities |  |  |  |  |  |
Assets: |  |  |  |  |  |
Marketable debt securities | 1,486.8 |  | 1,301.5 |  |  |
Fair Value, Measurements, Recurring | Government securities |  |  |  |  |  |
Assets: |  |  |  |  |  |
Marketable debt securities | 712.9 |  | 627.1 |  |  |
Fair Value, Measurements, Recurring | Mortgage and other asset backed securities |  |  |  |  |  |
Assets: |  |  |  |  |  |
Marketable debt securities | 181.9 |  | 122.4 |  |  |
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring |  |  |  |  |  |
Assets: |  |  |  |  |  |
Cash equivalents | 0.0 |  | 0.0 |  |  |
Marketable equity securities | 215.9 |  | 271.1 |  |  |
Derivative contracts | 0.0 |  | 0.0 |  |  |
Plan assets for deferred compensation | 0.0 |  | 0.0 |  |  |
Total | 215.9 |  | 271.1 |  |  |
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 | 978.9 |  | 626.9 |  |  |
Marketable equity securities | 950.3 |  | 1,703.2 |  |  |
Derivative contracts | 80.0 |  | 20.5 |  |  |
Plan assets for deferred compensation | 33.7 |  | 28.2 |  |  |
Total | 4,424.5 |  | 4,429.8 |  |  |
Liabilities: |  |  |  |  |  |
Derivative contracts | 27.7 |  | 217.2 |  |  |
Contingent consideration obligations | 0.0 |  | 0.0 |  |  |
Total | 27.7 |  | 217.2 |  |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate debt securities |  |  |  |  |  |
Assets: |  |  |  |  |  |
Marketable debt securities | 1,486.8 |  | 1,301.5 |  |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Government securities |  |  |  |  |  |
Assets: |  |  |  |  |  |
Marketable debt securities | 712.9 |  | 627.1 |  |  |
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities |  |  |  |  |  |
Assets: |  |  |  |  |  |
Marketable debt securities | 181.9 |  | 122.4 |  |  |
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 | 210.7 |  | 259.8 |  |  |
Total | 210.7 |  | 259.8 |  |  |
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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