ACQUISITIONS, DIVESTITURES, LICENSING AND OTHER ARRANGEMENTS - Narrative (Details) $ / shares in Units, $ in Millions					3 Months Ended	9 Months Ended		12 Months Ended		36 Months Ended
	May 13, 2025 USD ($) $ / shares	Mar. 18, 2024 USD ($) $ / shares	Feb. 26, 2024 USD ($) $ / shares	Jan. 23, 2024 USD ($) right $ / shares	Dec. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2026	Feb. 28, 2025 USD ($)
Licensing Arrangements [Line Items]
Business combination, contingent value, number of rights received | right				1
Philochem
Licensing Arrangements [Line Items]
License and other arrangements upfront payments						$ 350
Maximum aggregate contingent and regulatory milestone payments						1,000
BioArctic
Licensing Arrangements [Line Items]
License and other arrangements upfront payments						$ 100
Maximum aggregate contingent and regulatory milestone payments											$ 1,300
Forecast | Orbital Therapeutics | Subsequent Event
Licensing Arrangements [Line Items]
Business combination, consideration transferred					$ 1,500
Keytruda royalties
Licensing Arrangements [Line Items]
Percentage of net sales payable to alliance partner									6.50%
Keytruda royalties | Forecast
Licensing Arrangements [Line Items]
Percentage of net sales payable to alliance partner										2.50%
Keytruda royalties | Forecast | Bristol-Myers Squibb
Licensing Arrangements [Line Items]
Payment and royalty allocation										75.00%
Keytruda royalties | Forecast | Ono
Licensing Arrangements [Line Items]
Payment and royalty allocation										25.00%
Diabetes business - royalties
Licensing Arrangements [Line Items]
Percentage of net sales payable to alliance partner						14.00%		15.00%
RayzeBio
Licensing Arrangements [Line Items]
Share price (in usd per share) | $ / shares			$ 62.50
Total consideration			$ 4,147
Business combination, consideration transferred			3,600
RayzeBio | Unvested Equity Awards
Licensing Arrangements [Line Items]
Total consideration			$ 274
Mirati Therapeutics
Licensing Arrangements [Line Items]
Share price (in usd per share) | $ / shares				$ 58.00
Total consideration				$ 4,801
Business combination, consideration transferred				$ 4,100
Business combination, contingent value, share price (in dollars per share) | $ / shares				$ 12.00
Continent consideration liability				$ 1,000
Business combination, contingent value payout, period				7 years
2seventy bio
Licensing Arrangements [Line Items]
Asset acquisition, share price (in dollars per share) | $ / shares	$ 5.00
Payments to acquire assets	$ 287
Payments for asset acquisitions, net of cash acquired	$ 114
Karuna
Licensing Arrangements [Line Items]
Asset acquisition, share price (in dollars per share) | $ / shares		$ 330.00
Payments to acquire assets		$ 14,027
Payments for asset acquisitions, net of cash acquired		$ 12,900
Karuna | Acquired IPRD
Licensing Arrangements [Line Items]
Payments to acquire assets							$ 12,100