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Collaborative and Other Relationships Collaborative and Other Relationships - Collaborations (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
Jan. 31, 2019 | Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Inventory charges |  | $ 446.0 | $ 384.6 |
Research and development |  | 496.7 | 423.4 |
Other |  | 164.4 | 90.0 |
Collaboration profit (loss) sharing |  | 42.5 | 20.8 |
ZINBRYTA |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Inventory charges |  | 2.4 |  |
Research and development |  | $ 12.8 |  |
AbbVie |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Biogen share of co-promotion profits or losses |  | 50.00% |  |
Eisai | E2609 and BAN2401 |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Research and development |  | $ 26.1 | 20.8 |
Eisai | Aducanumab |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Research and development |  | 63.6 | 53.3 |
Scenario, Forecast | Eisai |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Percentage of future development costs related to Eisai | 45.00% |  |  | 15.00%
U.S. | AbbVie |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Other |  | 4.9 | $ 5.9 |
E.U. and Canada | AbbVie |  |  |  |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |  |  |  |
Collaboration profit (loss) sharing |  | $ 1.3 |  |

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- Definition Total costs related to goods produced and sold during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(a)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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- Definition The costs incurred in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, excluding in-process research and development acquired in a business combination consummated during the period. Excludes software research and development, which has a separate concept. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 730 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373 + Details
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