Supplemental Income Statement Information - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Net income attributable to Thermo Fisher Scientific Inc.	$ 6,335	$ 5,995	$ 6,950
Basic weighted average shares (in shares)	382	386	392
Plus effect of: stock options and restricted stock units (in shares)	1	2	2
Diluted weighted average shares (in shares)	383	388	394
Basic earnings per share (in dollars per share)	$ 16.58	$ 15.52	$ 17.75
Diluted earnings per share (in dollars per share)	$ 16.53	$ 15.45	$ 17.63
Antidilutive stock options excluded from diluted weighted averages shares (shares)	2	2	2