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Intangible Assets and Goodwill (Details 1) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016 | Feb. 01, 2017
Goodwill [Line Items] |  |  |  |  |
Increase to goodwill |  |  | $ 508.9 |  |
Income tax benefit (expense) | $ 269.6 | $ 353.6 | 508.8 | $ 710.0 |
Summary of roll forward of the changes in goodwill |  |  |  |  |
Goodwill, beginning of period |  |  | 3,669.3 |  |
Other |  |  | 6.3 |  |
Goodwill, end of period | $ 3,870.4 |  | 3,870.4 |  |
TECFIDERA | Fumapharm AG |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Increase to goodwill |  |  | 600.0 |  |
Income tax benefit (expense) |  |  | $ 91.1 |  |
Bioverativ |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Elimination of goodwill allocated to our hemophilia business |  |  |  |  | $ (314.1)

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