Employee Benefit Plan, Description of Plan (Details) - EBP 001 - USD ($) $ in Thousands		12 Months Ended
Apr. 01, 2026	Dec. 31, 2025	Dec. 31, 2024
EBP, Description of Plan [Line Items]
tmo_EBPEmployeeBenefitPlanParticipantContributionPretaxAndRothMaximumAnnualCompensationToTotalCompensationPercentage		75.00%
EBP, Participant Contribution, After Tax, Maximum Annual Contribution to Eligible Compensation, Percentage		8.00%
EBP, Participant Contribution, Automatic, Deferral Rate		3.00%
EBP, Employer Contribution, Matching Percentage		100.00%
EBP, Employer Contribution, Participant Compensation Matched, Percentage		6.00%
EBP, Vesting Percentage		100.00%
EBPVesting Service Requirement Period, Employer Contributions		2 years
EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount		$ 1
EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount		$ 50
EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage		50.00%
EBP, Note Receivable from Participant, Loan Term		5 years
EBP, Note Receivable from Participant, Loan Term for Primary Residence		30 years
EBP, Note Receivable from Participant, Interest Rate Range, Low End		3.25%	3.25%
EBP, Note Receivable from Participant, Interest Rate Range, High End		9.50%	9.75%
EBP, Forfeited Nonvested Account		$ 3,103	$ 5,904
EBP, Forfeited Nonvested Account, Decrease from Employer Contribution		$ 10,179
Subsequent Event
EBP, Description of Plan [Line Items]
EBP, Employer Contribution, Participant Compensation Matched, Percentage	5.00%

EBPEmployeeBenefitPlanParticipantContributionPretaxAndRothMaximumAnnualCompensationToTotalCompensationPercentage

No definition available.

Name:	tmo_EBPEmployeeBenefitPlanParticipantContributionPretaxAndRothMaximumAnnualCompensationToTotalCompensationPercentage
Namespace Prefix:	tmo_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

EBP, Note Receivable from Participant, Interest Rate Range, High End

+ References

No definition available.

+ Details

Name:	tmo_EBPNoteReceivableFromParticipantInterestRateRangeHighEnd
Namespace Prefix:	tmo_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

EBP, Note Receivable from Participant, Interest Rate Range, Low End

+ References

No definition available.

+ Details

Name:	tmo_EBPNoteReceivableFromParticipantInterestRateRangeLowEnd
Namespace Prefix:	tmo_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

EBP, Note Receivable from Participant, Loan Term

+ References

No definition available.

+ Details

Name:	tmo_EBPNoteReceivableFromParticipantLoanTerm
Namespace Prefix:	tmo_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

EBP, Note Receivable from Participant, Loan Term for Primary Residence

+ References

No definition available.

+ Details

Name:	tmo_EBPNoteReceivableFromParticipantLoanTermForPrimaryResidence
Namespace Prefix:	tmo_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

EBP, Participant Contribution, After Tax, Maximum Annual Contribution to Eligible Compensation, Percentage

+ References

No definition available.

+ Details

Name:	tmo_EBPParticipantContributionAfterTaxMaximumAnnualContributionToEligibleCompensationPercentage
Namespace Prefix:	tmo_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

EBP, Vesting Percentage

+ References

No definition available.

+ Details

Name:	tmo_EBPVestingPercentage
Namespace Prefix:	tmo_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

EBPVesting Service Requirement Period, Employer Contributions

+ References

No definition available.

+ Details

Name:	tmo_EBPVestingServiceRequirementPeriodEmployerContributions
Namespace Prefix:	tmo_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of employer matching contribution on eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of plan asset, in forfeited nonvested account, no longer allocated to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from employer contribution.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(5)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForEmployerContribution
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMinimumBorrowingAmount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantContributionAutomaticDeferralRate
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=tmo_EBP001Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: