Industry Segments - Schedule of reporting information by segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net sales	$ 132,258	$ 125,480	$ 372,902	$ 398,880
Total operating income	13,140	8,060	48,694	28,460
Interest expense, net	(1,204)	(993)	(3,467)	(3,059)
Income from continuing operations before income taxes	11,936	7,067	45,227	25,401
Operating Segments [Member] | Material Handling [Member]
Segment Reporting Information [Line Items]
Net sales	86,769	84,110	251,700	282,963
Total operating income	15,593	10,385	46,556	44,181
Operating Segments [Member] | Distribution [Member]
Segment Reporting Information [Line Items]
Net sales	45,517	41,388	121,253	115,957
Total operating income	5,091	3,382	8,577	6,923
Inter-company sales [Member]
Segment Reporting Information [Line Items]
Net sales	(28)	(18)	(51)	(40)
Corporate [Member]
Segment Reporting Information [Line Items]
Total operating income	$ (7,544)	$ (5,707)	$ (6,439)	$ (22,644)