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	190,407	$ 195,045	398,958	$ 437,712
Operating Income	15,056	14,889	36,963	49,397
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	11,396	11,185	30,128	42,000
Assets	1,011,401	991,734	1,011,401	991,734	977,839
Energy [Member]
Operations and assets by segment
Net Sales	91,377	97,601	207,850	235,703
Operating Income	32	8,195	8,627	26,948
Assets	551,035	543,141	551,035	543,141
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	423,587	449,228	423,587
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	25,006	11,138	25,006
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	156,672	141,038	326,670	295,438
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)