Restructuring and Other Costs, Net (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017		Feb. 26, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Percentage of Total Workforce Eliminated, Less Than										1.00%		1.00%		2.00%
Cost of Revenues										$ 17		$ 12		$ 123
Selling, General and Administrative Expenses										62		29		78
Restructuring and other (income) costs, net										(413)		50		97
Total Restructuring and Other Costs (Income), Net		$ 38	$ 43	$ (443)	$ 28	$ 42	$ (32)	$ 25	$ 56	(334)		91		298
Restructuring and Related Costs, Cash Costs										66	[1]	102	[2]	106	[3]
Restructuring and Related Costs, Other Costs (Income), Net										17		(38)		27
Loss (Gain) Related to Litigation-related Matter														(27)
Loss (Gain) on Divestiture of Businesses										$ (482)		0		0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, Statement of Income [Extensible List]										tmo:RestructuringAndOtherCostsIncomeNet
Abandonment of Excess Facilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Costs, Cash Costs										$ 7		33		27
Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Costs, Cash Costs										45		51		62
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Costs, Cash Costs	[4]									14		18		17
Life Sciences Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Cost of Revenues										16		4		1
Selling, General and Administrative Expenses												12		29
Restructuring and other (income) costs, net										24		(17)		(16)
Total Restructuring and Other Costs (Income), Net										40		(1)		14
Restructuring and Related Costs, Cash Costs														48
Loss (Gain) Related to Litigation-related Matter												(46)		(64)
Life Sciences Solutions [Member] | Abandonment of Excess Facilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Costs, Cash Costs														25
Life Sciences Solutions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Costs, Cash Costs														23
Analytical Instruments [Member]
Restructuring Cost and Reserve [Line Items]
Cost of Revenues												3		31
Selling, General and Administrative Expenses										24		8		(2)
Restructuring and other (income) costs, net										14		28		30
Total Restructuring and Other Costs (Income), Net										38		39		59
Specialty Diagnostics [Member]
Restructuring Cost and Reserve [Line Items]
Cost of Revenues														1
Selling, General and Administrative Expenses										4		3		(2)
Restructuring and other (income) costs, net										(471)		(1)		39
Total Restructuring and Other Costs (Income), Net										(467)		2		38
Loss (Gain) on Disposition of Property Plant Equipment												(6)
Laboratory Products and Services [Member]
Restructuring Cost and Reserve [Line Items]
Cost of Revenues										1		5		90
Selling, General and Administrative Expenses										35		16		61
Restructuring and other (income) costs, net										17		31		41
Total Restructuring and Other Costs (Income), Net										53		52		192
Laboratory Products and Services [Member] | Charges for Sales of Inventories Revalued at Acquisition [Member]
Restructuring Cost and Reserve [Line Items]
Cost of Revenues														55
Laboratory Products and Services [Member] | Costs to Conform Accounting Policies [Member]
Restructuring Cost and Reserve [Line Items]
Cost of Revenues														33
Selling, General and Administrative Expenses														6
Laboratory Products and Services [Member] | Transaction Costs Related to Acquisition [Member]
Restructuring Cost and Reserve [Line Items]
Selling, General and Administrative Expenses														55
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Selling, General and Administrative Expenses										(1)		(10)		(8)
Restructuring and other (income) costs, net										3		9		3
Total Restructuring and Other Costs (Income), Net										$ 2		$ (1)		(5)
Corporate [Member] | Product Liability, Workers Compensation and Other Personal Injury Matters [Member]
Restructuring Cost and Reserve [Line Items]
Selling, General and Administrative Expenses														$ (8)
Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Identified Future Restructuring Costs																$ 65

[1] Excludes $482 million of net gain on the sale of businesses, and $17 million of other restructuring charges, net, primarily for the impairment of acquired in-process research and development, pre-acquisition litigation-related matters, and compensation due to employees on the date of acquisition.

[2] Excludes $38 million of income, net, primarily associated with litigation-related matters, gains on sales of real estate, charges for environmental remediation, and hurricane response costs.

[3] Excludes $27 million of net credits associated with litigation-related matters, and $27 million of other restructuring charges, net, primarily for hurricane response/impairment, charges associated with the settlement/curtailment of retirement plans, and non-cash compensation due at an acquired business.

[4] Other includes relocation and moving expenses associated with facility consolidations, as well as employee retention costs which are accrued ratably over the period through which employees must work to qualify for a payment.