Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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Acquisitions - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
Acquisitions - Narrative (Details) - USD ($) $ in Millions	Jan. 03, 2023	Dec. 31, 2021	Dec. 31, 2020	Dec. 30, 2021	Dec. 08, 2021	Sep. 30, 2021	Feb. 25, 2021	Jan. 15, 2021
Business Acquisition [Line Items]
Weighted-average amortization period		14 years
The Binding Site Group \| Subsequent Event
Business Acquisition [Line Items]
Weighted-average amortization period	17 years
European Viral Vector Business
Business Acquisition [Line Items]
Goodwill recorded								$ 0
Mesa Biotech
Business Acquisition [Line Items]
Goodwill recorded							$ 0
Lengnau biologics manufacturing facility
Business Acquisition [Line Items]
Goodwill recorded						$ 0
PPD
Business Acquisition [Line Items]
Goodwill recorded					$ 0
Net income attributable to Thermo Fisher Scientific Inc.		$ 7,369	$ 5,361
Pro forma revenues		378
Pro forma losses		(60)
PPD \| Non-recurring Pro Forma Adjustments, Transaction Costs
Business Acquisition [Line Items]
Net income attributable to Thermo Fisher Scientific Inc.		$ 312	$ (197)
PeproTech
Business Acquisition [Line Items]
Goodwill recorded				$ 0
Customer relationships
Business Acquisition [Line Items]
Weighted-average amortization period		17 years
Product technology
Business Acquisition [Line Items]
Weighted-average amortization period		11 years
Tradenames
Business Acquisition [Line Items]
Weighted-average amortization period		7 years
Backlog
Business Acquisition [Line Items]
Weighted-average amortization period		3 years