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Debt - Narrative (Details) - USD ($) | 1 Months Ended | 3 Months Ended |
--- | --- | --- | ---
Aug. 31, 2020 | Sep. 30, 2020 | May 31, 2020
Senior Unsecured Notes |  |  |
Line of Credit Facility [Line Items] |  |  |
Redemption price, percentage | 100.00% |  |
Redemption price with change-in-control provision, percentage | 101.00% |  |
Interest expense |  | $ 6,400,000 |
Bridge Facility | Common Stock Held By Sanofi | Bridge Facility |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt, principal amount |  |  | $ 1,500,000,000
2030 Notes | Senior Unsecured Notes |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt, principal amount | $ 1,250,000,000 |  |
Interest rate | 1.75% |  |
2050 Notes | Senior Unsecured Notes |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt, principal amount | $ 750,000,000 |  |
Interest rate | 2.80% |  |

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