Document And Entity Information (USD $)	12 Months Ended
	Dec. 27, 2014	Feb. 13, 2015	Jun. 28, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	LITTELFUSE INC /DE
Document Type	10-K
Current Fiscal Year End Date	--12-27
Entity Common Stock, Shares Outstanding		22,593,248
Entity Public Float			$ 2,080,104,238
Amendment Flag	false
Entity Central Index Key	0000889331
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	Dec. 27, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY