REVENUE RECOGNITION - Variable Consideration Provisions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 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	3,697	3,860
Payments and credits	(3,845)	(4,104)
Reserve ending balance	1,902	2,156
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	457	585
Payments and credits	(454)	(583)
Reserve ending balance	185	177
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	71	50
Payments and credits	(185)	(187)
Reserve ending balance	577	679
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	1,587	1,650
Payments and credits	(1,605)	(1,673)
Reserve ending balance	909	1,013
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	1,433	1,425
Payments and credits	(1,451)	(1,480)
Reserve ending balance	150	154
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	149	150
Payments and credits	(150)	(181)
Reserve ending balance	$ 81	$ 133