v3.3.1.900
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