Document And Entity Information - USD ($)	12 Months Ended
	Jan. 02, 2016	Feb. 19, 2016	Jun. 27, 2015
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)		22,342,813
Entity Public Float			$ 2,201,579,542
Document Type	10-K
Document Period End Date	Jan. 02, 2016
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Amendment Flag	false