Business Combinations and Asset Acquisitions (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Apr. 16, 2021 |
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
|
| Business Acquisition [Line Items] | |||||
| Payments to Acquire Businesses, Net of Cash Acquired | $ 1,639 | $ 0 | |||
| Acquired in-process research and development | $ 0 | $ 0 | $ 1,505 | $ 0 | |
| Five Prime Therapeutics, Inc. | |||||
| Business Acquisition [Line Items] | |||||
| Payments to Acquire Businesses, Net of Cash Acquired | $ 1,600 | ||||
| Acquired in-process research and development | 1,500 | ||||
| Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other | 47 | ||||
| Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets | $ 177 | ||||