Operating segments (Details) (USD $)	3 Months Ended								12 Months Ended
	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2013		Feb. 29, 2012		Feb. 28, 2011
Operations and assets by segment
Net sales	$ 140,391,000	$ 149,675,000	$ 153,385,000	$ 127,143,000	$ 123,625,000	$ 116,493,000	$ 114,661,000	$ 114,333,000	$ 570,594,238		$ 469,112,410		$ 380,649,407
Segment Operating income									122,035,000	[1]	98,736,000	[1]	84,037,000	[1]
General corporate expenses									23,706,000	[2]	21,636,000	[2]	21,492,000	[2]
Interest expense									13,072,605		13,939,149		7,730,556
Other (income) expense, net									(9,113,000)	[3]	(480,000)	[3]	(144,000)	[3]
Total expenses									27,666,000		35,095,000		29,079,000
Income before income taxes									94,369,000		63,641,000		54,958,000
Depreciation and amortization									29,363,000		22,595,000		22,166,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									161,981,000		47,147,000		120,502,000
Total assets	694,205,000				606,775,000				694,205,000		606,775,000		566,525,000
Goodwill	171,886,270				121,383,863				171,886,270		121,383,863		113,463,000
Electrical and Industrial Products [Member]
Operations and assets by segment
Net sales									233,555,000		189,192,000		162,600,000
Segment Operating income									34,228,000	[1]	25,772,000	[1]	27,072,000	[1]
Depreciation and amortization									8,587,000		3,317,000		3,396,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									79,513,000		3,161,000		1,282,000
Total assets	260,874,000				143,208,000				260,874,000		143,208,000		136,381,000
Goodwill	75,151,000				43,331,000				75,151,000		43,331,000		43,492,000
Galvanizing Services [Member]
Operations and assets by segment
Net sales									337,039,000		279,920,000		218,049,000
Segment Operating income									87,807,000	[1]	72,964,000	[1]	56,965,000	[1]
Depreciation and amortization									19,501,000		17,783,000		17,004,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									81,604,000		43,298,000		117,746,000
Total assets	370,142,000				309,808,000				370,142,000		309,808,000		277,366,000
Goodwill	96,735,000				78,053,000				96,735,000		78,053,000		69,971,000
Corporate [Member]
Operations and assets by segment
Depreciation and amortization									1,275,000		1,495,000		1,766,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									864,000		688,000		1,474,000
Total assets	$ 63,189,000				$ 153,759,000				$ 63,189,000		$ 153,759,000		$ 152,778,000

[1] Segment operating income consisted of net sales less cost of sales, specifically identifiable selling, general and administrative expenses and other income and expense items that are specifically identifiable to a segment.

[2] General Corporate Expense consisted of selling, general and administrative expenses that are not specifically identifiable to a segment.

[3] Other (income) expense, net included gains and losses on sale of property, plant and equipment and other (income) expenses not specifically identifiable to a segment.