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Collaborative and Other Relationships - ADUHELM Collaboration Agreement (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2023 | Dec. 31, 2022 | Mar. 31, 2022
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Percentage of future development costs related to Eisai | 45.00% |  |
Excess and obsolescence charges related to inventory | $ 17.4 |  | $ 281.5
ADUHELM |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Excess and obsolescence charges related to inventory |  | $ 275.0 | 275.0
ADUHELM | Maximum |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Research and development expense asset acquired | 335.0 |  |
ADUHELM | Cost of Sales |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Excess and obsolescence charges related to inventory |  |  | $ 45.0
Eisai |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Percentage of future development costs related to Eisai |  |  | 45.00%
Amounts receivable | 72.6 | 88.0 |
Amounts payable | 137.8 | $ 81.2 |
Eisai | Collaboration profit sharing |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Recognized net reductions to operating expense | $ 181.7 |  |
Eisai | ADUHELM | Inventory, Idle Capacity Charges And Contractual Commitments |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |
Recognized net reductions to operating expense |  |  | $ 160.0

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- Definition Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 50 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=116847112&loc=d3e4542-108314 + Details
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- Definition The aggregate costs incurred (1) 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 (2) 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, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 912 -SubTopic 730 -Section 25 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6472174&loc=d3e58812-109433 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 730 -SubTopic 10 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373 + Details
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