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Employee Benefits - Summary of Stock-Based Compensation (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |  |
Stock-based compensation expense included in total costs and expenses | $ 635 | $ 1,076 | $ 636
Income tax effect | (100) | (222) | 2
Stock-based compensation expense, net of tax | 535 | 854 | 638
Stock-based compensation expense | 635 | 643 | 636
Income tax expense following U.S. Court of Appeals decision |  |  | 114
Forty Seven, Inc. |  |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |  |
Accelerated stock-based expense |  | 144 |
Immunomedics, Inc. |  |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |  |
Accelerated stock-based expense |  | 289 |
Cost of goods sold |  |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |  |
Stock-based compensation expense included in total costs and expenses | 40 | 109 | 48
Research and development expenses |  |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |  |
Stock-based compensation expense included in total costs and expenses | 287 | 462 | 289
Selling, general and administrative expenses |  |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |  |
Stock-based compensation expense included in total costs and expenses | $ 308 | $ 505 | $ 299

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