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Financial Instruments Financial Instruments (Details Textual 2) - USD ($) shares in Millions, $ in Millions | Mar. 31, 2019 | Dec. 31, 2018 | Jun. 05, 2018
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Strategic Investments |  |  |
Business Acquisition [Line Items] |  |  |
Strategic investment portfolio | $ 1,049.7 |  |
Ionis Pharmaceuticals |  |  |
Business Acquisition [Line Items] |  |  |
Investment in common stock, shares purchased |  |  | 11.5
Purchase of common stock |  |  | $ 625.0
Other current assets | Strategic Investments |  |  |
Business Acquisition [Line Items] |  |  |
Strategic investment portfolio | $ 90.1 |  |
Other noncurrent assets | Strategic Investments |  |  |
Business Acquisition [Line Items] |  |  |
Strategic investment portfolio |  | $ 676.3 |

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