v2.4.0.8
Document and Entity Information (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Jun. 30, 2013
Mar. 01, 2014
Class A Common Stock [Member]
Mar. 01, 2014
Class B Common Stock [Member]
Entity Information [Line Items]        
Entity Registrant Name BEL FUSE INC /NJ      
Entity Central Index Key 0000729580      
Current Fiscal Year End Date --12-31      
Entity Well-known Seasoned Issuer No      
Entity Voluntary Filers No      
Entity Current Reporting Status Yes      
Entity Filer Category Accelerated Filer      
Entity Public Float   $ 140.9    
Entity Common Stock, Shares Outstanding     2,174,912 9,335,677
Document Fiscal Year Focus 2013      
Document Fiscal Period Focus FY      
Document Type 10-K      
Amendment Flag false      
Document Period End Date Dec. 31, 2013