Collaborative Arrangements - Schedule of Transactions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Cost of sales	3,481	3,990	9,952	10,443
Selling, general and administrative	2,450	2,589	7,383	7,726
Research and development	3,390	3,204	7,721	7,324
Payables, current	20,405		20,405		$ 22,220
Other current assets | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	197		197		128
Other current assets | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	170		170		150
Other current assets | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	70		70		49
Accounts payable and accrued liabilities | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, current	309		309		577
Payables, Noncurrent	400		400		0
Accounts payable and accrued liabilities | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, current	325		325		700
Other Noncurrent Liabilities | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, Noncurrent	570		570		525
Other Noncurrent Liabilities | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, Noncurrent	375		375		$ 375
Revenue | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	199	123	522	313
Revenue | AstraZeneca | Collaborative Arrangement | Alliance revenue - Lynparza (1)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	196	123	519	313
Revenue | AstraZeneca | Collaborative Arrangement | Alliance revenue - Koselugo
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	3	0	3	0
Revenue | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	142	109	421	280
Revenue | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	83	50	216	144
Collaborative Arrangement, Sales, Net	55	57	167	158
Sales	138	107	383	302
Cost of sales | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	41	28	205	120
Cost of sales | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	46	23	215	97
Cost of sales | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	29	28	85	86
Selling, general and administrative | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	40	36	112	96
Selling, general and administrative | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	18	21	48	59
Selling, general and administrative | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	19	12	42	31
Research and development | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	20	44	93	122
Research and development | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	48	37	168	146
Research and development | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	$ 12	$ 31	$ 53	$ 94