Note 3 - Acquisition and Divestiture - Schedule of Pro Forma Information (Details) - Enercon Technologies, Ltd [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Revenue, net	$ 152,238	$ 158,805
Net earnings	18,322	18,022
Less: Net earnings attributable to non-controlling interest	448	1,085
Net earnings attributable to Bel Fuse shareholders	$ 17,874	$ 16,937
Common Class A [Member]
Earnings per common share - basic and diluted (in dollars per share)	$ 1.36	$ 1.27
Common Class B [Member]
Earnings per common share - basic and diluted (in dollars per share)	$ 1.43	$ 1.34