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FAIR VALUE MEASUREMENTS - Summary of Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | --- | ---
Other publicly traded equity securities |  |  |
Assets: |  |  |
Total | $ 4,774 |  | $ 6,970
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement |  |  |
Assets: |  |  |
Total | 7,318 |  | 9,008
Liabilities: |  |  |
Total | 585 |  | 339
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | MYR GmbH |  |  |
Liabilities: |  |  |
Liability for MYR GmbH (“MYR”) contingent consideration | 328 |  | 0
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | U.S. treasury securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 360 |  | 309
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | U.S. government agencies securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 5 |  | 0
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Non-U.S. government securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 44 |  | 43
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Certificates of deposit |  |  |
Assets: |  |  |
Available-for-sale debt securities | 361 |  | 216
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Corporate debt securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 1,272 |  | 1,142
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Residential mortgage and asset-backed securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 447 |  | 316
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Money market funds |  |  |
Assets: |  |  |
Marketable equity securities | 2,768 |  | 4,361
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Equity investment in Galapagos |  |  |
Assets: |  |  |
Marketable equity securities | 881 |  | 1,648
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Other publicly traded equity securities |  |  |
Assets: |  |  |
Marketable equity securities | 876 |  | 743
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Other publicly traded equity securities | Arcus |  |  |
Assets: |  |  |
Marketable equity securities | 482 |  | 212
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Deferred compensation plan |  |  |
Assets: |  |  |
Marketable equity securities | 249 |  | 218
Liabilities: |  |  |
Deferred compensation plan | 249 |  | 218
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Foreign currency derivative contracts |  |  |
Assets: |  |  |
Foreign currency derivative contracts | 55 |  | 12
Liabilities: |  |  |
Foreign currency derivative contracts | 8 |  | 121
Fair Value, Measurements, Recurring | Level 1 |  |  |
Assets: |  |  |
Total | 5,134 |  | 7,279
Liabilities: |  |  |
Total | 249 |  | 218
Fair Value, Measurements, Recurring | Level 1 | MYR GmbH |  |  |
Liabilities: |  |  |
Liability for MYR GmbH (“MYR”) contingent consideration | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 | U.S. treasury securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 360 |  | 309
Fair Value, Measurements, Recurring | Level 1 | U.S. government agencies securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 | Non-U.S. government securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 | Certificates of deposit |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 | Residential mortgage and asset-backed securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 1 | Money market funds |  |  |
Assets: |  |  |
Marketable equity securities | 2,768 |  | 4,361
Fair Value, Measurements, Recurring | Level 1 | Equity investment in Galapagos |  |  |
Assets: |  |  |
Marketable equity securities | 881 |  | 1,648
Fair Value, Measurements, Recurring | Level 1 | Other publicly traded equity securities |  |  |
Assets: |  |  |
Marketable equity securities | 876 |  | 743
Fair Value, Measurements, Recurring | Level 1 | Deferred compensation plan |  |  |
Assets: |  |  |
Marketable equity securities | 249 |  | 218
Liabilities: |  |  |
Deferred compensation plan | 249 |  | 218
Fair Value, Measurements, Recurring | Level 1 | Foreign currency derivative contracts |  |  |
Assets: |  |  |
Foreign currency derivative contracts | 0 |  | 0
Liabilities: |  |  |
Foreign currency derivative contracts | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 |  |  |
Assets: |  |  |
Total | 2,184 |  | 1,729
Liabilities: |  |  |
Total | 8 |  | 121
Fair Value, Measurements, Recurring | Level 2 | MYR GmbH |  |  |
Liabilities: |  |  |
Liability for MYR GmbH (“MYR”) contingent consideration | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | U.S. treasury securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | U.S. government agencies securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 5 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Non-U.S. government securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 44 |  | 43
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit |  |  |
Assets: |  |  |
Available-for-sale debt securities | 361 |  | 216
Fair Value, Measurements, Recurring | Level 2 | Corporate debt securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 1,272 |  | 1,142
Fair Value, Measurements, Recurring | Level 2 | Residential mortgage and asset-backed securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 447 |  | 316
Fair Value, Measurements, Recurring | Level 2 | Money market funds |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Equity investment in Galapagos |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Other publicly traded equity securities |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Deferred compensation plan |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Liabilities: |  |  |
Deferred compensation plan | 0 |  | 0
Fair Value, Measurements, Recurring | Level 2 | Foreign currency derivative contracts |  |  |
Assets: |  |  |
Foreign currency derivative contracts | 55 |  | 12
Liabilities: |  |  |
Foreign currency derivative contracts | 8 |  | 121
Fair Value, Measurements, Recurring | Level 3 |  |  |
Assets: |  |  |
Total | 0 |  | 0
Liabilities: |  |  |
Total | 328 |  | 0
Fair Value, Measurements, Recurring | Level 3 | MYR GmbH |  |  |
Liabilities: |  |  |
Liability for MYR GmbH (“MYR”) contingent consideration | 328 | $ 341 | 0
Fair Value, Measurements, Recurring | Level 3 | U.S. treasury securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | U.S. government agencies securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Non-U.S. government securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Certificates of deposit |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Residential mortgage and asset-backed securities |  |  |
Assets: |  |  |
Available-for-sale debt securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Money market funds |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Equity investment in Galapagos |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Other publicly traded equity securities |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Deferred compensation plan |  |  |
Assets: |  |  |
Marketable equity securities | 0 |  | 0
Liabilities: |  |  |
Deferred compensation plan | 0 |  | 0
Fair Value, Measurements, Recurring | Level 3 | Foreign currency derivative contracts |  |  |
Assets: |  |  |
Foreign currency derivative contracts | 0 |  | 0
Liabilities: |  |  |
Foreign currency derivative contracts | $ 0 |  | $ 0

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