Acquisitions Purchase Price (Details) $ in Millions	1 Months Ended
Sep. 26, 2020 USD ($)
QIAGEN N.V. (Terminated Acquisition) [Member]
Net Assets Acquired [Abstract]
Business Acquisition, Terminated, Reimbursement of Transaction Costs Received	$ 95

Reimbursement, upon termination of an acquisition agreement, of transaction costs incurred in an attempt to complete the business combination.

No definition available.

Name:	tmo_BusinessAcquisitionTerminatedReimbursementOfTransactionCosts
Namespace Prefix:	tmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration