| Earnings Per Share [Text Block] |
The following table sets forth the calculation of basic and diluted net earnings per common share under the two-class method for the three and nine months ended September 30, 2026 and 2025:
| | | Three Months Ended | | | Nine Months Ended | |
| | | September 30, | | | September 30, | |
| | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| | | | | | | | | | | | | | | | | |
| Numerator: | | | | | | | | | | | | | | | | |
| Net earnings attributable to Bel Fuse shareholders | | $ | 26,290 | | | $ | 22,250 | | | $ | 63,149 | | | $ | 66,985 | |
| Less dividends declared: | | | | | | | | | | | | | | | | |
| Class A | | | 127 | | | | 127 | | | | 381 | | | | 381 | |
| Class B | | | 863 | | | | 741 | | | | 2,342 | | | | 2,218 | |
| Undistributed earnings | | $ | 25,300 | | | $ | 21,382 | | | $ | 60,426 | | | $ | 64,386 | |
| | | | | | | | | | | | | | | | | |
| Undistributed earnings allocation: | | | | | | | | | | | | | | | | |
| Basic - Class A undistributed earnings | | $ | 3,557 | | | $ | 3,429 | | | $ | 9,037 | | | $ | 10,349 | |
| Basic - Class B undistributed earnings | | | 21,743 | | | | 17,953 | | | | 51,389 | | | | 54,037 | |
| Total undistributed earnings | | $ | 25,300 | | | $ | 21,382 | | | $ | 60,426 | | | $ | 64,386 | |
| | | | | | | | | | | | | | | | | |
| Net earnings allocation: | | | | | | | | | | | | | | | | |
| Basic - Class A net earnings | | $ | 3,684 | | | $ | 3,556 | | | $ | 9,418 | | | $ | 10,730 | |
| Basic - Class B net earnings | | | 22,606 | | | | 18,694 | | | | 53,731 | | | | 56,255 | |
| Basic - Net earnings | | $ | 26,290 | | | $ | 22,250 | | | $ | 63,149 | | | $ | 66,985 | |
| | | | | | | | | | | | | | | | | |
| Undistributed earnings allocation: | | | | | | | | | | | | | | | | |
| Diluted - Class A undistributed earnings | | $ | 3,554 | | | $ | 3,429 | | | $ | 9,031 | | | $ | 10,349 | |
| Diluted - Class B undistributed earnings | | | 21,746 | | | | 17,953 | | | | 51,395 | | | | 54,037 | |
| Total undistributed earnings | | $ | 25,300 | | | $ | 21,382 | | | $ | 60,426 | | | $ | 64,386 | |
| | | | | | | | | | | | | | | | | |
| Net earnings allocation: | | | | | | | | | | | | | | | | |
| Diluted - Class A net earnings | | $ | 3,681 | | | $ | 3,556 | | | $ | 9,412 | | | $ | 10,730 | |
| Diluted - Class B net earnings | | | 22,609 | | | | 18,694 | | | | 53,737 | | | | 56,255 | |
| Diluted - Net earnings | | $ | 26,290 | | | $ | 22,250 | | | $ | 63,149 | | | $ | 66,985 | |
| | | | | | | | | | | | | | | | | |
| Denominator: | | | | | | | | | | | | | | | | |
| Weighted-average shares outstanding: | | | | | | | | | | | | | | | | |
| Class A - Basic | | | 2,115 | | | | 2,115 | | | | 2,115 | | | | 2,115 | |
| Class A - Diluted | | | 2,115 | | | | 2,115 | | | | 2,115 | | | | 2,115 | |
| Class B - Basic | | | 12,312 | | | | 10,548 | | | | 11,455 | | | | 10,519 | |
| Class B - Diluted | | | 12,324 | | | | 10,548 | | | | 11,465 | | | | 10,519 | |
| | | | | | | | | | | | | | | | | |
| Net earnings per share: | | | | | | | | | | | | | | | | |
| Class A - Basic | | $ | 1.74 | | | $ | 1.68 | | | $ | 4.45 | | | $ | 5.07 | |
| Class A - Diluted | | $ | 1.74 | | | $ | 1.68 | | | $ | 4.45 | | | $ | 5.07 | |
| Class B - Basic | | $ | 1.84 | | | $ | 1.77 | | | $ | 4.69 | | | $ | 5.35 | |
| Class B - Diluted | | $ | 1.83 | | | $ | 1.77 | | | $ | 4.69 | | | $ | 5.35 | |
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