Consolidated Statement of Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Non- controlling Interests
Beginning balance at Dec. 31, 2021	$ 38,257	$ 1,788	$ 44,238	$ 53,696	$ (4,429)	$ (57,109)	$ 73
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Merck & Co., Inc.	14,519			14,519
Other comprehensive income (loss), net of taxes	(339)				(339)
Cash dividends declared on common stock	(7,134)			(7,134)
Net income attributable to noncontrolling interests	7						7
Distributions attributable to noncontrolling interests	(13)						(13)
Share-based compensation plans and other	761		141			620
Ending balance at Dec. 31, 2022	46,058	1,788	44,379	61,081	(4,768)	(56,489)	67
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Merck & Co., Inc.	365			365
Other comprehensive income (loss), net of taxes	(393)				(393)
Cash dividends declared on common stock	(7,551)			(7,551)
Treasury stock shares purchased	(1,346)					(1,346)
Net income attributable to noncontrolling interests	12						12
Distributions attributable to noncontrolling interests	(25)						(25)
Share-based compensation plans and other	515		130			385
Ending balance at Dec. 31, 2023	37,635	1,788	44,509	53,895	(5,161)	(57,450)	54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Merck & Co., Inc.	17,117			17,117
Other comprehensive income (loss), net of taxes	216				216
Cash dividends declared on common stock	(7,943)			(7,943)
Treasury stock shares purchased	(1,306)					(1,306)
Net income attributable to noncontrolling interests	16						16
Distributions attributable to noncontrolling interests	(12)						(12)
Share-based compensation plans and other	649		195			453	1
Ending balance at Dec. 31, 2024	$ 46,372	$ 1,788	$ 44,704	$ 63,069	$ (4,945)	$ (58,303)	$ 59