GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets (Details) - USD ($) $ in Millions	1 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 04, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount		$ 25,715			$ 22,897
Accumulated Amortization		(7,495)			(6,660)
Foreign Currency Translation Adjustment		1			(1)
Net Carrying Amount		18,221			16,236
Intangible Assets, Net (Including Goodwill) [Abstract]
Gross  Carrying Amount		41,835			39,787
Accumulated Amortization		(7,495)			(6,660)
Foreign Currency Translation Adjustment		1			(1)
Net Carrying Amount		34,341			33,126
Acquired IPR&D
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Gross  Carrying Amount		16,120			16,890
Foreign Currency Translation Adjustment		0			0
Net Carrying Amount		16,120			16,890
Intangible Assets, Net (Including Goodwill) [Abstract]
Intangible assets reclassified from indefinite-lived assets		(910)
Reclassified amounts	$ 1,000
Acquired IPR&D | MYR GmbH
Intangible Assets, Net (Including Goodwill) [Abstract]
Acquired IPR&D			$ 1,200	$ 1,190
Intangible asset - sofosbuvir
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount		10,720			10,720
Accumulated Amortization		(5,302)			(4,952)
Foreign Currency Translation Adjustment		0			0
Net Carrying Amount		5,418			5,768
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization		(5,302)			(4,952)
Intangible asset - axicabtagene ciloleucel
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount		7,110			6,200
Accumulated Amortization		(1,298)			(1,105)
Foreign Currency Translation Adjustment		0			0
Net Carrying Amount		5,812			5,095
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization		(1,298)			(1,105)
Intangible assets reclassified from indefinite-lived assets		910
Intangible asset - Trodelvy
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount		5,630			4,600
Accumulated Amortization		(274)			(63)
Foreign Currency Translation Adjustment		0			0
Net Carrying Amount		5,356			4,537
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization		(274)			(63)
Reclassified amounts	$ 1,000
Intangible asset - Hepcludex for HDV
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount		845			0
Accumulated Amortization		(29)			0
Foreign Currency Translation Adjustment		0			0
Net Carrying Amount		816			0
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization		(29)			0
Other
Finite-Lived Intangible Assets [Line Items]
Gross  Carrying Amount		1,410			1,377
Accumulated Amortization		(592)			(540)
Foreign Currency Translation Adjustment		1			(1)
Net Carrying Amount		819			836
Intangible Assets, Net (Including Goodwill) [Abstract]
Accumulated Amortization		$ (592)			$ (540)