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Acquisitions, Research Collaborations and Licensing Agreements - Narrative (Details) $ / shares in Units, $ in Millions | 1 Months Ended | 6 Months Ended | 12 Months Ended | 20 Months Ended |
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Feb. 29, 2024 USD ($) | Jun. 30, 2023 USD ($) | Feb. 28, 2023 USD ($) antibodyDrugConjugate | Jan. 31, 2023 USD ($) | Oct. 31, 2022 USD ($) | Aug. 31, 2022 USD ($) | Jul. 31, 2022 USD ($) | May 31, 2022 USD ($) | Nov. 30, 2021 USD ($) | Apr. 30, 2021 USD ($) | Mar. 31, 2021 USD ($) | Jun. 30, 2024 USD ($) $ / shares | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2023 USD ($) | Oct. 31, 2023 USD ($) antibodyDrugConjugate
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  |  |  | $ 30,531 | $ 13,548 | $ 12,245 |  |
Harpoon Therapeutics, Inc. | Subsequent Event | Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Asset acquisition, share price (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  | $ 23 |  |  |  |  |
Consideration transferred, asset acquisition |  |  |  |  |  |  |  |  |  |  |  | $ 680 |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  |  | $ 650 |  |  |  |  |
Prometheus Biosciences, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred, asset acquisition |  | $ 11,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  |  |  | 10,200 |  |  |  |
Consideration transferred, to settle share-based equity awards |  | 1,200 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred, to settle equity awards, unvested |  | 700 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net assets acquired |  | 877 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash recorded for asset acquisition |  | 368 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments recorded for asset acquisition |  | 296 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred tax assets recorded for asset acquisition |  | 218 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other net liabilities recorded for asset acquisition |  | $ 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Imago BioSciences, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred, asset acquisition |  |  |  | $ 1,350 |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  |  |  | 1,200 |  |  |  |
Net assets acquired |  |  |  | 219 |  |  |  |  |  |  |  |  |  |  |  |  |
Transaction costs |  |  |  | 60 |  |  |  |  |  |  |  |  |  |  |  |  |
Pandion Therapeutics |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consideration transferred, asset acquisition |  |  |  |  |  |  |  |  |  | $ 1,900 |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,700 |  |
Consideration transferred, to settle share-based equity awards |  |  |  |  |  |  |  |  |  | 147 |  |  |  |  |  |  |
Other net assets (liabilities) |  |  |  |  |  |  |  |  |  | $ 156 |  |  |  |  |  |  |
Elanco Animal Health Incorporated Aqua Business | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash paid for acquisition of business | $ 1,300 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Acceleron Pharma Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash paid for acquisition of business |  |  |  |  |  |  |  |  | $ 11,500 |  |  |  |  |  |  |  |
Transaction costs |  |  |  |  |  |  |  |  | $ 280 |  |  |  |  |  |  |  |
Daiichi Sankyo | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development |  |  |  |  |  |  |  |  |  |  |  |  | 5,500 |  |  |  |
Number of antibody drug conjugates obtained right and obligations | antibodyDrugConjugate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3
Orna Therapeutics | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Upfront payment made to collaborative partner |  |  |  |  |  | $ 150 |  |  |  |  |  |  |  |  |  |  |
Eligible future contingent development-related payments (up to) |  |  |  |  |  | 440 |  |  |  |  |  |  |  |  |  |  |
Aggregate, regulatory milestones payments, maximum |  |  |  |  |  | 675 |  |  |  |  |  |  |  |  |  |  |
Sales milestone payments |  |  |  |  |  | $ 2,400 |  |  |  |  |  |  |  |  |  |  |
Preferred stock investment in counterparty |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 100 |  |  |
Orion Corporation | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Upfront payment made to collaborative partner |  |  |  |  |  |  | $ 290 |  |  |  |  |  |  |  |  |  |
Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of antibody drug conjugates obtained right and obligations | antibodyDrugConjugate |  |  | 7 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Upfront payment made to collaborative partner |  |  | $ 175 |  |  |  | 35 |  |  |  |  |  |  |  |  |  |
Number of antibody drug conjugates terminated with collaborative partner | antibodyDrugConjugate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2
Eligible future contingent development-related payments (up to) |  |  |  |  |  |  | 82 | $ 90 |  |  |  |  |  |  |  |  | $ 725
Aggregate, regulatory milestones payments, maximum |  |  |  |  |  |  | 334 |  |  |  |  |  |  |  |  |  | 1,950
Sales milestone payments |  |  |  |  |  |  | $ 485 | 780 |  |  |  |  |  |  |  |  | $ 3,900
Stock investment in counterparty |  |  |  | $ 100 |  |  |  |  |  |  |  |  |  |  |  |  |
Option payment made to collaborative partner |  |  |  |  |  |  |  | 30 |  |  |  |  |  |  |  |  |
Milestone payment to be made to a collaborative partner |  |  |  |  |  |  |  |  |  |  |  |  | $ 25 |  |  |  |
Research and development payments to be made to a collaborative partners |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 111 |
Research and development payments made to a collaborative partner |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 95 |
Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | First Commercial Sale Milestones |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales milestone payments |  |  |  |  |  |  |  | $ 290 |  |  |  |  |  |  |  |  |
Bristol Myers Squibb | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Royalty rate, percentage |  |  |  |  |  |  |  |  | 22.00% |  |  |  |  |  |  |  |
Gilead Sciences | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Oral and Injectable Formulations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Profit share by counterparty |  |  |  |  |  |  |  |  |  |  | 60.00% |  |  |  |  |  |
Profit share |  |  |  |  |  |  |  |  |  |  | 40.00% |  |  |  |  |  |
Gilead Sciences | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Oral Formulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Profit share by counterparty |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |
Profit share |  |  |  |  |  |  |  |  |  |  | 35.00% |  |  |  |  |  |
Sales threshold |  |  |  |  |  |  |  |  |  |  | $ 2,000 |  |  |  |  |  |
Gilead Sciences | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Injectable Formulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Profit share by counterparty |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |
Profit share |  |  |  |  |  |  |  |  |  |  | 35.00% |  |  |  |  |  |
Sales threshold |  |  |  |  |  |  |  |  |  |  | $ 3,500 |  |  |  |  |  |
Royalty Pharma |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Compensation earned on arragement |  |  |  |  | $ 50 |  |  |  |  |  |  |  |  |  |  |  |
Additional funding by others, percentage of development costs |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |
Additional funding by others, development costs subject to funding |  |  |  |  | $ 375 |  |  |  |  |  |  |  |  |  |  |  |

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