Charge for Expired Tax Credits due to Audit Settlement

No definition available.

Name:	tmo_ChargeForExpiredTaxCreditsDueToAuditSettlement
Namespace Prefix:	tmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Effective Income Tax Rate Reconciliation, Foreign Exchange Loss On Debt Refinancing, Net Of Expenses

+ References

No definition available.

+ Details

Name:	tmo_EffectiveIncomeTaxRateReconciliationForeignExchangeLossOnDebtRefinancingNetOfExpenses
Namespace Prefix:	tmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 35
-Paragraph 2
-SubTopic 740
-Topic 718
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480887/718-740-35-2

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

+ References

No definition available.

+ Details

Name:	us-gaap_IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

+ References

+ Details

Name:	us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to disposition of asset. Includes, but is not limited to, intra-entity transfer of asset other than inventory.

+ References

+ Details

Name:	us-gaap_IncomeTaxReconciliationDispositionOfAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_IncomeTaxReconciliationTaxContingencies
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_IncomeTaxReconciliationTaxCreditsResearch
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements.

+ References

+ Details

Name:	us-gaap_IncomeTaxReconciliationTaxSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-3

+ Details

Name:	us-gaap_OperatingLossCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

No definition available.

+ Details

Name:	us-gaap_OperatingLossCarryforwardsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

+ Details

Name:	us-gaap_TaxCreditCarryforwardAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of undistributed earnings of foreign subsidiaries intended to be permanently reinvested outside the country of domicile.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 25
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482620/740-10-25-3

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-SubTopic 740
-Topic 942
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481141/942-740-50-1

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-SubTopic 740
-Topic 944
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480135/944-740-50-1

+ Details

Name:	us-gaap_UndistributedEarningsOfForeignSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482525/740-10-45-10B

+ Details

Name:	us-gaap_UnrecognizedTaxBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-15

+ Details

Name:	us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase in unrecognized tax benefits resulting from acquisitions.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A

+ Details

Name:	us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=tmo_ForeignTaxCreditCarryforwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=tmo_DeferredTaxAssetInterestCarryforwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TaxPeriodAxis=tmo_TaxYears20252033Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_DomesticCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=tmo_DomesticNOLExpiresMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=tmo_StateNOLExpiresMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=tmo_ForeignCountryNolExpiresMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_DomesticCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=tmo_ForeignTaxPositionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=tmo_FederalAndStateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tmo_IntraEntityAxis=tmo_DeferredTaxImplicationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tmo_IntraEntityAxis=tmo_CapitalLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Provision for (reversal of) valuation allowances, net	$ (32)	$ 344	$ 36
Tax benefit from foreign exchange loss on an intercompany debt refinancing transaction	91
Research credits and incentives	127
Intra-entity transfers	(233)	(18)	(284)
Tax return reassessments and settlements	187	210	(1)
Excess tax benefits from stock options and restricted stock units	(69)	(80)	(124)
Undistributed earnings	34,000
Unrecognized tax benefits	540	572	1,124	$ 1,091
Additions due to acquisitions	0	15	26
UTB, interest and penalties	95	74
Foreign Tax Credit Carryforwards
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	648
Deferred Interest Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	753
Deferred Interest Carryforward \| Tax Years 2025-2033
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	149
Federal
Operating Loss Carryforwards [Line Items]
NOL carryforwards	70
Domestic NOL Expires
Operating Loss Carryforwards [Line Items]
NOL carryforwards	30
State
Operating Loss Carryforwards [Line Items]
NOL carryforwards	93
State NOL Expires
Operating Loss Carryforwards [Line Items]
NOL carryforwards	83
Non- U.S.
Operating Loss Carryforwards [Line Items]
NOL carryforwards	1,420
Portion of Non- U.S. with expiration dates
Operating Loss Carryforwards [Line Items]
NOL carryforwards	435
Federal
Operating Loss Carryforwards [Line Items]
Provision for (reversal of) valuation allowances, net		395
Tax return reassessments and settlements		208
Provision for (reversal of) tax reserves, net		658
Charge for expired tax credits		49
Unrecognized tax benefits reclassed to accrued income taxes in connection with IRS settlement		101
Foreign
Operating Loss Carryforwards [Line Items]
Increase (decrease) in UTB	12	(143)	(80)
Federal and State
Operating Loss Carryforwards [Line Items]
Increase (decrease) in UTB	$ 19	$ 610	75
Deferred Tax Implications
Operating Loss Carryforwards [Line Items]
Intra-entity transfers			188
Capital Loss
Operating Loss Carryforwards [Line Items]
Intra-entity transfers			$ 96