Goodwill and Intangible Assets - Indefinite-Lived Intangible Assets (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Indefinite-lived intangible assets | |||
| Indefinite-lived research and development assets | $ 1,877,000,000 | $ 0 | |
| Indefinite-lived intangible assets impairment charges | $ 0 | ||
| In-process research and development | Stemcentrx Inc. | |||
| Indefinite-lived intangible assets | |||
| Indefinite-lived intangible assets impairment charges | $ 1,000,000,000.0 | $ 5,100,000,000 | |