CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Sales	$ 15,962	$ 14,959	$ 45,485	$ 45,453
Costs, Expenses and Other
Cost of sales	4,264	3,934	12,214	13,530
Selling, general and administrative	2,519	2,520	7,700	7,355
Research and development	3,307	4,399	20,904	9,773
Restructuring costs	126	94	344	288
Other (income) expense, net	126	429	388	1,576
Total Costs, Expenses and Other	10,342	11,376	41,550	32,522
Income Before Taxes	5,620	3,583	3,935	12,931
Taxes on Income	870	330	2,332	1,423
Net Income	4,750	3,253	1,603	11,508
Less: Net Income Attributable to Noncontrolling Interests	5	5	12	6
Net Income Attributable to Merck & Co., Inc.	$ 4,745	$ 3,248	$ 1,591	$ 11,502
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.87	$ 1.28	$ 0.63	$ 4.55
Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.86	$ 1.28	$ 0.62	$ 4.53