Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2017	Aug. 31, 2016	Feb. 28, 2017
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	$ 230,314		$ 230,314		$ 228,610
Operations and assets by segment
Net Sales	196,329	$ 200,790	401,612	$ 451,156
Operating Income	17,387	15,107	37,410	51,416
Interest Expense	3,400	3,580	6,760	7,505
Gain (Loss) on Disposition of Property Plant Equipment	654	192	554	82
Other Nonoperating Income (Expense)	(394)	(68)	(479)	(190)
Income Before Income Taxes	13,727	11,403	30,575	44,019
Assets	1,009,582		1,009,582		978,354
Energy [Member]
Operations and assets by segment
Net Sales	97,299	103,346	210,504	249,147
Operating Income	2,363	8,413	9,074	28,967
Assets	549,216		549,216		536,557
Galvanizing Services [Member]
Operations and assets by segment
Net Sales	99,030	97,444	191,108	202,009
Operating Income	23,409	15,032	44,651	39,334
Assets	449,228		449,228		428,330
Corporate, Non-Segment [Member]
Operations and assets by segment
Operating Income	(8,385)	(8,338)	(16,315)	(16,885)
Corporate [Member]
Operations and assets by segment
Assets	11,138		11,138		13,467
UNITED STATES
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	206,298		206,298		205,079
Operations and assets by segment
Net Sales	162,594	146,783	329,323	308,881
CANADA
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	18,169		18,169		18,002
Other Countries [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	5,847		5,847		$ 5,529
International [Member]
Operations and assets by segment
Net Sales	33,839	54,163	72,393	142,970
Geography Eliminations [Member]
Operations and assets by segment
Net Sales	$ (104)	$ (156)	$ (104)	$ (695)