v2.4.0.8
Document and Entity Information
6 Months Ended
Jun. 30, 2015
Aug. 01, 2015
Class A Common Stock [Member]
Aug. 01, 2015
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 Common Stock, Shares Outstanding   2,174,912 9,723,727
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus Q2    
Document Type 10-Q    
Amendment Flag false    
Document Period End Date Jun. 30, 2015