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Cover Page - USD ($)
 12 Months Ended
Dec. 27, 2025
Feb. 13, 2026
Jun. 28, 2025
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 27, 2025    
Document Transition Report false    
Entity File Number 0-20388    
Entity Registrant Name LITTELFUSE INC /DE    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 36-3795742    
Entity Address, Street 6133 North River Road    
Entity Address, Suite Suite 500    
Entity Address, City Rosemont    
Entity Address, State IL    
Entity Address, Postal Zip Code 60018    
City Area Code 773    
Local Phone Number 628-1000    
Title of Each Class Common Stock, $0.01 par value    
Trading Symbol LFUS    
Name of Each Exchange On Which Registered NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction false    
Entity Shell Company false    
Entity Public Float     $ 5,591,411,587
Entity Common Stock, Shares Outstanding   25,107,673  
Documents Incorporated by Reference
Portions of the Littelfuse, Inc. Proxy Statement for the 2026 Annual Meeting of Stockholders (the “Proxy Statement”) are incorporated by reference into Part III of this Form 10-K.
    
Entity Central Index Key 0000889331    
Current Fiscal Year End Date --12-27    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false