REVENUE RECOGNITION - Variable Consideration Provisions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reserve beginning balance	$ 2,050	$ 2,384
Acquisition of Synergy		16
Current period provisions	1,337	1,261
Payments and credits	(1,392)	(1,415)
Reserve ending balance	1,995	2,246
Discounts and Allowances
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reserve beginning balance	182	175
Acquisition of Synergy		0
Current period provisions	156	204
Payments and credits	(167)	(210)
Reserve ending balance	171	169
Returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reserve beginning balance	691	813
Acquisition of Synergy		3
Current period provisions	42	33
Payments and credits	(75)	(55)
Reserve ending balance	658	794
Rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reserve beginning balance	927	1,024
Acquisition of Synergy		12
Current period provisions	602	533
Payments and credits	(588)	(568)
Reserve ending balance	941	1,001
Chargebacks
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reserve beginning balance	168	209
Acquisition of Synergy		0
Current period provisions	484	443
Payments and credits	(501)	(497)
Reserve ending balance	151	155
Distribution Fees
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reserve beginning balance	82	163
Acquisition of Synergy		1
Current period provisions	53	48
Payments and credits	(61)	(85)
Reserve ending balance	$ 74	$ 127