Operating segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 29, 2020
Operations and assets by segment
Sales	$ 902,664	$ 838,917	$ 1,061,817
Operating income (loss)	113,340	61,614	79,343
Loss on disposal of business	552	3,080	18,632
Depreciation	44,665	44,603	50,194
Expenditures for acquisitions, net of cash, and property, plant and equipment:	89,624	41,498	93,223
Assets:	1,133,028	999,227
Property, plant and equipment, net	230,848	207,089
Asset impairment charges	13,700	9,200
Corporate
Operations and assets by segment
Operating income (loss)	(49,538)	(40,819)	(42,796)
Loss on disposal of business	0	0	(18,632)
Depreciation	1,628	1,695	1,738
Expenditures for acquisitions, net of cash, and property, plant and equipment:	2,073	2,574	2,725
Assets:	32,854	25,678
United States
Operations and assets by segment
Sales	789,047	711,696	850,656
Property, plant and equipment, net	194,539	181,898
International
Operations and assets by segment
Sales	113,617	127,221	211,161
Canada
Operations and assets by segment
Property, plant and equipment, net	26,264	15,007
Other countries
Operations and assets by segment
Property, plant and equipment, net	10,045	10,184
Metal Coatings | Operating Segments
Operations and assets by segment
Sales	519,000	457,791	498,989
Operating income (loss)	127,335	95,946	107,926
Loss on disposal of business		1,221
Depreciation	30,000	29,930	30,042
Expenditures for acquisitions, net of cash, and property, plant and equipment:	82,737	29,305	81,340
Assets:	575,088	480,778
Infrastructure Solutions | Operating Segments
Operations and assets by segment
Sales	383,664	381,126	562,828
Operating income (loss)	35,543	6,487	32,845
Loss on disposal of business		1,859
Depreciation	13,037	12,978	18,414
Expenditures for acquisitions, net of cash, and property, plant and equipment:	4,814	9,619	$ 9,158
Assets:	$ 525,086	492,771
Asset impairment charges		9,200
Infrastructure Solutions | Operating Segments | Selling, general and administrative
Operations and assets by segment
Asset impairment charges		7,200
Infrastructure Solutions | Operating Segments | Cost of sales
Operations and assets by segment
Asset impairment charges		$ 2,000