Document And Entity Information - shares	3 Months Ended
	Apr. 02, 2016	Apr. 29, 2016
Entity Registrant Name	LITTELFUSE INC /DE
Entity Central Index Key	0000889331
Trading Symbol	lfus
Current Fiscal Year End Date	--01-02
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding (in shares)		22,422,545
Document Type	10-Q
Document Period End Date	Apr. 02, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1
Amendment Flag	false