Revenue from Contracts with Customers - Schedule of Sales Reserves and Allowances (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue Recognition [Line Items]
Balance at beginning of period	$ 4,904	$ 6,246
Provisions related to sales made in current year	3,532	4,100
Provisions related to sales made in prior periods	(117)	(148)
Credits and payments	(3,628)	(4,410)
Translation differences	(29)	(43)
Balance at end of period	4,662	5,745
Reserves Included in Accounts Receivable, Net [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	80	87
Provisions related to sales made in current year	100	102
Credits and payments	(102)	(106)
Balance at end of period	78	83
Rebates [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	2,054	2,895
Provisions related to sales made in current year	1,126	1,370
Provisions related to sales made in prior periods	(55)	(106)
Credits and payments	(1,210)	(1,513)
Translation differences	(17)	(21)
Balance at end of period	1,898	2,625
Medicaid and Other Governmental Allowances [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	828	1,109
Provisions related to sales made in current year	164	233
Provisions related to sales made in prior periods	(11)	(29)
Credits and payments	(188)	(248)
Translation differences	(4)	(2)
Balance at end of period	789	1,063
Chargebacks [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	1,108	1,342
Provisions related to sales made in current year	2,043	2,223
Provisions related to sales made in prior periods	6	(16)
Credits and payments	(1,987)	(2,396)
Translation differences	(3)	(6)
Balance at end of period	1,167	1,147
Returns [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	686	637
Provisions related to sales made in current year	76	139
Provisions related to sales made in prior periods	(40)	(1)
Credits and payments	(101)	(112)
Translation differences	(3)	(4)
Balance at end of period	618	659
Other [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	148	176
Provisions related to sales made in current year	23	33
Provisions related to sales made in prior periods	(17)	4
Credits and payments	(40)	(35)
Translation differences	(2)	(10)
Balance at end of period	112	168
Total Reserves Included in Sales Reserves and Allowances [Member]
Revenue Recognition [Line Items]
Balance at beginning of period	4,824	6,159
Provisions related to sales made in current year	3,432	3,998
Provisions related to sales made in prior periods	(117)	(148)
Credits and payments	(3,526)	(4,304)
Translation differences	(29)	(43)
Balance at end of period	$ 4,584	$ 5,662