Income Taxes - Schedule of Deferred Tax Asset (Liability) and Changes in Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Deferred Tax Assets (Liabilities) [Abstract]
Depreciation and amortization	$ (4,133)	$ (4,286)
Net operating loss and credit carryforwards	2,915	2,385
Reserves and accruals	161	157
Accrued compensation	318	299
Inventory basis difference	309	275
Deferred interest	534	753
Research and development and other capitalized costs	536	380
Unrealized (gains) losses on hedging instruments	(363)	(66)
Contract liabilities	280	130
Other, net	147	199
Deferred tax assets/(liabilities), net before valuation allowance	705	226
Less: Valuation allowance	1,043	1,317	$ 1,322
Deferred tax assets/(liabilities), net	(338)	(1,091)
Valuation Allowance [Roll Forward]
Beginning Balance	1,317	1,322	968
Additions/(reductions) recognized in income tax provision, net	(229)	(32)	344
Additions due to acquisitions	0	4	14
Currency translation and other	(46)	23	(4)
Ending Balance	$ 1,043	$ 1,317	$ 1,322

Deferred Tax Asset, Contract Liabilities

No definition available.

Name:	tmo_DeferredTaxAssetContractLiabilities
Namespace Prefix:	tmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

For entities that net deferred tax assets and tax liabilities, represents the unclassified net amount of deferred tax assets, before any related valuation allowance, and liabilities as of the balance sheet date, which result from applying the applicable enacted tax rate to net temporary differences and carryforwards pertaining to assets or liabilities. A temporary difference is a difference between the tax basis of an asset or liability and its carrying amount in the financial statements prepared in accordance with generally accepted accounting principles that will reverse in ensuing periods.

+ References

No definition available.