Consolidated Statement of (Loss) Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Sales	$ 60,115	$ 59,283	$ 48,704
Costs, Expenses and Other
Cost of sales	16,126	17,411	13,626
Selling, general and administrative	10,504	10,042	9,634
Research and development	30,531	13,548	12,245
Restructuring costs	599	337	661
Other (income) expense, net	466	1,501	(1,341)
Total costs, expenses and other	58,226	42,839	34,825
Income from Continuing Operations Before Taxes	1,889	16,444	13,879
Taxes on Income from Continuing Operations	1,512	1,918	1,521
Net Income from Continuing Operations	377	14,526	12,358
Less: Net Income Attributable to Noncontrolling Interests	12	7	13
Net Income from Continuing Operations Attributable to Merck & Co., Inc.	365	14,519	12,345
Income from Discontinued Operations, Net of Taxes and Amounts Attributable to Noncontrolling Interests	0	0	704
Net Income Attributable to Merck & Co., Inc.	$ 365	$ 14,519	$ 13,049
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders
Income from Continuing Operations (in dollars per share)	$ 0.14	$ 5.73	$ 4.88
Income from Discontinued Operations (in dollars per share)	0	0	0.28
Net Income (in dollars per share)	0.14	5.73	5.16
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders
Income from Continuing Operations (in dollars per share)	0.14	5.71	4.86
Income from Discontinued Operations (in dollars per share)	0	0	0.28
Net Income (in dollars per share)	$ 0.14	$ 5.71	$ 5.14