Document and Entity Information	6 Months Ended
	Jun. 30, 2018 shares
Document and Entity Information [Abstract]
Entity Registrant Name	THERMO FISHER SCIENTIFIC INC.
Entity Central Index Key	0000097745
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	402,796,251
Entity Stock Trading Symbol	TMO