Document And Entity Information - shares	6 Months Ended
	Jun. 27, 2015	Jul. 24, 2015
Entity Registrant Name	LITTELFUSE INC /DE
Entity Central Index Key	0000889331
Current Fiscal Year End Date	--12-28
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		22,647,323
Document Type	10-Q
Document Period End Date	Jun. 27, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q2
Amendment Flag	false