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Fair Value Measurements (Details Textual) - USD ($) | 6 Months Ended |
--- | --- | ---
Jun. 30, 2019 | Dec. 31, 2018
Business Acquisition, Contingent Consideration [Line Items] |  |
Asset impairment charges | $ 0 |
Fair value measurements, changes in valuation inputs | 0 |
Contingent consideration obligations | $ 255,100,000 | $ 265,000,000.0
2.900% Senior Notes due 2020 |  |
Business Acquisition, Contingent Consideration [Line Items] |  |
Senior Notes interest rate | 2.90% |
3.625% Senior Notes due 2022 |  |
Business Acquisition, Contingent Consideration [Line Items] |  |
Senior Notes interest rate | 3.625% |
4.050% Senior Notes due 2025 |  |
Business Acquisition, Contingent Consideration [Line Items] |  |
Senior Notes interest rate | 4.05% |
5.200% Senior Notes due 2045 |  |
Business Acquisition, Contingent Consideration [Line Items] |  |
Senior Notes interest rate | 5.20% |

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