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Collaborative and Other Relationships - Summary of Activity Related to LEQEMBI Collaboration (Details) - LEQEMBI - Alzheimer's collaboration revenue - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2025 | Mar. 31, 2024
Collaborative arrangements and non-collaborative arrangement transactions |  |
Expense reflected within statements of income | $ 26.3 | $ 43.6
Total development expense incurred by the collaboration related to the advancement of LEQEMBI | 52.6 | 87.3
Selling, general and administrative |  |
Collaborative arrangements and non-collaborative arrangement transactions |  |
Expense reflected within statements of income | 88.8 | 86.9
Expense incurred by the collaboration | $ 177.7 | $ 173.9

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