GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount	$ 31,819		$ 31,819	$ 25,794
Accumulated Amortization	(12,436)		(12,436)	(10,121)
Foreign Currency Translation Adjustment	1		1	1
Total	19,384		19,384	15,674
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Gross  Carrying Amount	7,070		7,070	13,220
Foreign Currency Translation Adjustment	0		0	0
Net Carrying Amount	7,070		7,070	13,220
Intangible Assets, Net (Including Goodwill) [Abstract]
Gross  Carrying Amount	38,889		38,889	39,014
Accumulated Amortization	(12,436)		(12,436)	(10,121)
Foreign Currency Translation Adjustment	1		1	1
Net Carrying Amount	26,454		26,454	28,894
Write-off of finite-lived intangible asset			2,300	1,800	$ 1,700
In-process research and development impairments			50	2,700	$ 0
Fair Value, Nonrecurring | Galapagos
Intangible Assets, Net (Including Goodwill) [Abstract]
Write-off of finite-lived intangible asset	51
In Process Research And Development Trodelvy For HR+/HER2-
Intangible Assets, Net (Including Goodwill) [Abstract]
Indefinite-lived intangible assets, fair value	6,100	$ 6,100	6,100
In Process Research And Development Trodelvy For HR+/HER2- | Fair Value, Nonrecurring
Intangible Assets, Net (Including Goodwill) [Abstract]
In-process research and development impairments		$ 2,700		2,700
In Process Research And Development Bulveritide
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Gross  Carrying Amount	1,100		1,100
Intangible Assets, Net (Including Goodwill) [Abstract]
In-process research and development impairments	50
In Process Research And Development Bulveritide | Fair Value, Nonrecurring
Intangible Assets, Net (Including Goodwill) [Abstract]
In-process research and development impairments	50
In Process Research And Development NSCLC
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Gross  Carrying Amount	5,900		5,900
Intangible asset – sofosbuvir
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount	10,720		10,720	10,720
Accumulated Amortization	(7,050)		(7,050)	(6,350)
Foreign Currency Translation Adjustment	0		0	0
Total	3,670		3,670	4,370
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization	(7,050)		(7,050)	(6,350)
Intangible asset – axicabtagene ciloleucel
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount	7,110		7,110	7,110
Accumulated Amortization	(2,314)		(2,314)	(1,908)
Foreign Currency Translation Adjustment	0		0	0
Total	4,796		4,796	5,202
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization	(2,314)		(2,314)	(1,908)
Intangible asset – Trodelvy
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount	11,730		11,730	5,630
Accumulated Amortization	(2,002)		(2,002)	(973)
Foreign Currency Translation Adjustment	0		0	0
Total	9,728		9,728	4,657
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization	(2,002)		(2,002)	(973)
Intangible asset – Hepcludex
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount	845		845	845
Accumulated Amortization	(243)		(243)	(158)
Foreign Currency Translation Adjustment	0		0	0
Total	602		602	687
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization	(243)		(243)	(158)
Other
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount	1,414		1,414	1,489
Accumulated Amortization	(827)		(827)	(733)
Foreign Currency Translation Adjustment	1		1	1
Total	588		588	758
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization	$ (827)		$ (827)	$ (733)