RESTRUCTURING NARRATIVE (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020
Celgene Integration [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	$ 3,000
Restructuring and Related Cost, Cost Incurred to Date	2,100
Cash outlays	$ 2,500
Restructuring and Related Cost, Number of Positions Eliminated	65	600
MyoKardia Acquisition Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	$ 150
Restructuring and Related Cost, Cost Incurred to Date	76
Operating Model 2020 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 1,500