Condensed Consolidated Statement of Redeemable Noncontrolling Interest and Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock, $1.00 par value	Capital in Excess of Par Value	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Items	Total Thermo Fisher Scientific Inc. Shareholders’ Equity	Noncontrolling Interests
Beginning Balance at Dec. 31, 2021	$ 122
Redeemable Noncontrolling Interest [Roll Forward]
Net income/(loss)	14
Other comprehensive income/(loss)	(10)
Contributions from (distributions to) noncontrolling interests	(7)
Ending Balance at Oct. 01, 2022	119
Balance (in shares) at Dec. 31, 2021		439,000,000
Beginning Balance at Dec. 31, 2021	40,855	$ 439	$ 16,174	$ 35,431	$ (8,922)	$ (2,329)	$ 40,793	$ 62
Treasury stock beginning balance (in shares) at Dec. 31, 2021					45,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employees' and directors' stock plans (in shares)		1,000,000
Issuance of shares under employees' and directors' stock plans	102	$ 1	190		$ (89)		102
Stock-based compensation	232		232				232
Purchases of company common stock (in shares)					3,000,000
Purchases of company common stock	(2,000)				$ (2,000)		(2,000)
Dividends declared	(353)			(353)			(353)
Net income/(loss)	5,372			5,374			5,374	(2)
Other comprehensive items	(599)					(599)	(599)
Contributions from (distributions to) noncontrolling interests	(1)							(1)
Balance (in shares) at Oct. 01, 2022		440,000,000
Treasury stock ending balance (in shares) at Oct. 01, 2022					48,000,000
Ending Balance at Oct. 01, 2022	43,608	$ 440	16,596	40,452	$ (11,011)	(2,928)	43,549	59
Beginning Balance at Jul. 02, 2022	117
Redeemable Noncontrolling Interest [Roll Forward]
Net income/(loss)	5
Other comprehensive income/(loss)	(3)
Ending Balance at Oct. 01, 2022	119
Balance (in shares) at Jul. 02, 2022		440,000,000
Beginning Balance at Jul. 02, 2022	42,354	$ 440	16,467	39,074	$ (10,964)	(2,724)	42,293	61
Treasury stock beginning balance (in shares) at Jul. 02, 2022					48,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employees' and directors' stock plans	5		52		$ (47)		5
Stock-based compensation	77		77				77
Dividends declared	(117)			(117)			(117)
Net income/(loss)	1,493			1,495			1,495	(2)
Other comprehensive items	(204)					(204)	(204)
Balance (in shares) at Oct. 01, 2022		440,000,000
Treasury stock ending balance (in shares) at Oct. 01, 2022					48,000,000
Ending Balance at Oct. 01, 2022	43,608	$ 440	16,596	40,452	$ (11,011)	(2,928)	43,549	59
Beginning Balance at Dec. 31, 2022	116
Redeemable Noncontrolling Interest [Roll Forward]
Net income/(loss)	14
Other comprehensive income/(loss)	(5)
Contributions from (distributions to) noncontrolling interests	(7)
Ending Balance at Sep. 30, 2023	118
Balance (in shares) at Dec. 31, 2022		441,000,000
Beginning Balance at Dec. 31, 2022	$ 44,032	$ 441	16,743	41,910	$ (12,017)	(3,099)	43,978	54
Treasury stock beginning balance (in shares) at Dec. 31, 2022	50,157,275				50,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employees' and directors' stock plans (in shares)		1,000,000			1,000,000
Issuance of shares under employees' and directors' stock plans	$ 131	$ 1	205		$ (75)		131
Stock-based compensation	217		217				217
Purchases of company common stock (in shares)					5,000,000
Purchases of company common stock	(3,000)				$ (3,000)		(3,000)
Dividends declared	(406)			(406)			(406)
Net income/(loss)	4,335			4,365			4,365	(30)
Other comprehensive items	67					72	72	(5)
Contributions from (distributions to) noncontrolling interests	(1)							(1)
Excise tax from stock repurchases	$ (29)				$ (29)		(29)
Balance (in shares) at Sep. 30, 2023		442,000,000
Treasury stock ending balance (in shares) at Sep. 30, 2023	55,517,179				56,000,000
Ending Balance at Sep. 30, 2023	$ 45,346	$ 442	17,165	45,869	$ (15,121)	(3,027)	45,328	18
Beginning Balance at Jul. 01, 2023	113
Redeemable Noncontrolling Interest [Roll Forward]
Net income/(loss)	6
Other comprehensive income/(loss)	(1)
Ending Balance at Sep. 30, 2023	118
Balance (in shares) at Jul. 01, 2023		441,000,000
Beginning Balance at Jul. 01, 2023	43,802	$ 441	17,030	44,289	$ (15,084)	(2,924)	43,752	50
Treasury stock beginning balance (in shares) at Jul. 01, 2023					55,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under employees' and directors' stock plans (in shares)		1,000,000			1,000,000
Issuance of shares under employees' and directors' stock plans	32	$ 1	68		$ (37)		32
Stock-based compensation	67		67				67
Dividends declared	(135)			(135)			(135)
Net income/(loss)	1,689			1,715			1,715	(26)
Other comprehensive items	(108)					(103)	(103)	(5)
Contributions from (distributions to) noncontrolling interests	$ (1)							(1)
Balance (in shares) at Sep. 30, 2023		442,000,000
Treasury stock ending balance (in shares) at Sep. 30, 2023	55,517,179				56,000,000
Ending Balance at Sep. 30, 2023	$ 45,346	$ 442	$ 17,165	$ 45,869	$ (15,121)	$ (3,027)	$ 45,328	$ 18