Note 16 - Segments - Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Net sales	$ 178,980	$ 123,638	$ 499,517	$ 384,933
Cost of sales	107,840	78,961	304,475	238,782
Gross profit	$ 71,140	$ 44,677	$ 195,042	$ 146,151
Gross profit %	39.70%	36.10%	39.00%	38.00%
Research and development costs	$ 7,549	$ 5,443	$ 22,875	$ 16,652
Selling, general and administrative expenses	32,804	26,700	93,225	75,785
Restructuring charges	219	1,087	(2,434)	1,790
Gain on sale of property	(1,626)	0	(5,701)	0
Earnout liability adjustment	1,857	0	1,857	0
Interest expense	3,630	414	11,775	1,263
Interest income	(238)	(1,480)	(777)	(3,741)
Other income, net	(1,058)	1,325	(11,265)	(21)
Earnings before provision for income taxes	28,003	11,188	85,487	54,423
Total Assets	952,804	584,417	952,804	584,417	$ 949,789
Capital Expenditures	1,860	3,628	8,578	7,906
Depreciation and Amortization Expense	6,652	3,636	19,936	10,759
Power Solutions and Protection Segment [Member] \| Operating Segments [Member]
Net sales	94,406	48,680	264,259	167,478
Cost of sales	54,907	29,513	153,029	95,059
Gross profit	$ 39,499	$ 19,167	$ 111,230	$ 72,419
Gross profit %	41.80%	39.40%	42.10%	43.20%
Interest expense	$ 46	$ 127	$ 246	$ 410
Total Assets	654,182	189,091	654,182	189,091
Capital Expenditures	487	1,082	4,258	2,363
Depreciation and Amortization Expense	4,510	1,583	13,503	4,686
Connectivity Solutions [Member] \| Operating Segments [Member]
Net sales	61,870	55,715	171,802	167,822
Cost of sales	36,935	35,310	104,463	105,287
Gross profit	$ 24,935	$ 20,405	$ 67,339	$ 62,535
Gross profit %	40.30%	36.60%	39.20%	37.30%
Interest expense	$ 0	$ 6	$ 3	$ 64
Total Assets	184,840	232,572	184,840	232,572
Capital Expenditures	1,279	2,073	4,043	4,723
Depreciation and Amortization Expense	1,760	1,735	5,279	5,112
Magnetic Solutions [Member] \| Operating Segments [Member]
Net sales	22,704	19,243	63,456	49,633
Cost of sales	16,109	13,998	45,902	37,772
Gross profit	$ 6,595	$ 5,245	$ 17,554	$ 11,861
Gross profit %	29.00%	27.30%	27.70%	23.90%
Interest expense	$ (7)	$ 0	$ (7)	$ 0
Total Assets	53,736	57,832	53,736	57,832
Capital Expenditures	48	182	222	375
Depreciation and Amortization Expense	238	190	729	598
Corporate Segment [Member] \| Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Net sales	0	0	0	0
Cost of sales	(111)	140	1,081	664
Gross profit	111	(140)	(1,081)	(664)
Interest expense	3,591	281	11,533	789
Total Assets	60,046	104,922	60,046	104,922
Capital Expenditures	46	291	55	445
Depreciation and Amortization Expense	$ 144	$ 128	$ 425	$ 363

BEL FUSE INC /NJ 10-Q