Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	May 31, 2017	May 31, 2016	Feb. 28, 2017
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	$ 230,127		$ 228,610
Operations and assets by segment
Net Sales	205,283	$ 250,366
Operating Income	20,023	36,309
Interest Expense	3,360	3,925
Gain (Loss) on Disposition of Property Plant Equipment	(100)	(110)
Other Nonoperating Income (Expense)	(85)	(122)
Income Before Income Taxes	16,848	32,616
Assets	1,004,740		978,354
Energy [Member]
Operations and assets by segment
Net Sales	113,206	145,801
Operating Income	6,711	20,554
Assets	558,123		536,557
Galvanizing Services [Member]
Operations and assets by segment
Net Sales	92,077	104,565
Operating Income	21,242	24,302
Assets	432,516		428,330
Corporate, Non-Segment [Member]
Operations and assets by segment
Operating Income	(7,930)	(8,547)
Corporate [Member]
Operations and assets by segment
Assets	14,101		13,467
UNITED STATES
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	207,149		205,079
Operations and assets by segment
Net Sales	166,730	196,359
CANADA
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	17,369		18,002
Other Countries [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	5,609		$ 5,529
International [Member]
Operations and assets by segment
Net Sales	38,553	54,163
Geography Eliminations [Member]
Operations and assets by segment
Net Sales	$ 0	$ (156)