Industry Segments - Schedule of reporting information by segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net sales	$ 187,369	$ 118,394	$ 361,798	$ 240,644
Total operating income	15,869	12,256	26,734	35,554
Interest expense, net	(999)	(1,194)	(1,994)	(2,263)
Income before income taxes	14,870	11,062	24,740	33,291
Operating Segments [Member] | Material Handling [Member]
Segment Reporting Information [Line Items]
Net sales	137,227	80,855	267,120	164,931
Total operating income	17,902	15,796	34,829	30,963
Operating Segments [Member] | Distribution [Member]
Segment Reporting Information [Line Items]
Net sales	50,156	37,541	94,706	75,736
Total operating income	4,214	1,636	5,652	3,486
Inter-company sales [Member]
Segment Reporting Information [Line Items]
Net sales	(14)	(2)	(28)	(23)
Corporate [Member]
Segment Reporting Information [Line Items]
Total operating income	$ (6,247)	$ (5,176)	$ (13,747)	$ 1,105