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Collaborative and Other Relationships - ADUHELM Collaboration Agreement (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2022 | Mar. 31, 2022 | Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Income (loss) from equity method investments |  |  |  |  | $ 2.6 | $ 34.9 | $ 3.3
Royalty cost of sales |  |  |  |  | 2,278.3 | 2,109.7 | 1,805.2
Regulatory Milestones | Neurimmune |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Upfront and milestone payments made to collaborative partner |  |  |  |  |  | 100.0 | 75.0
ADUHELM |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Research and development expense asset acquired |  |  |  |  | 335.0 |  |
Income (loss) from equity method investments |  |  |  |  | 111.0 | 30.0 |
Royalty cost of sales | $ 164.0 | $ 275.0 |  |  |  |  |
Eisai |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Additional milestone payment |  |  |  |  | 0.0 | 100.0 | 75.0
Income (loss) from equity method investments |  |  |  | $ 33.8 | 0.0 | 45.0 | 33.8
Amounts receivable | 88.0 |  |  |  | 88.0 | 285.4 |
Amounts payable | $ 81.2 |  |  |  | $ 81.2 | 46.5 |
Eisai | Milestone Payments |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Percentage of future development costs |  |  |  |  | 45.00% |  |
Eisai | Collaboration profit sharing |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Recognized net reductions to operating expense |  |  |  |  | $ 224.7 | 233.2 |
Eisai | ADUHELM |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Income (loss) from equity method investments |  |  | $ 45.0 |  |  | 59.0 |
Eisai | ADUHELM | Milestone Payments |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Recognized net reductions to operating expense |  |  |  |  |  | 45.0 | $ 33.8
Eisai | ADUHELM | Inventory, Idle Capacity Charges And Contractual Commitments |  |  |  |  |  |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |  |  |  |  |  |
Recognized net reductions to operating expense |  |  |  |  | $ 197.0 | $ 99.0 |

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