Operating segments (Details) (USD $)	3 Months Ended								12 Months Ended
	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 28, 2014		Feb. 28, 2013		Feb. 29, 2012
Operations and assets by segment
Net sales	$ 181,011,000	$ 197,755,000	$ 189,782,000	$ 183,175,000	$ 140,391,000	$ 149,675,000	$ 153,385,000	$ 127,143,000	$ 751,723,398		$ 570,594,238		$ 469,112,410
Segment Operating income									137,849,000	[1]	122,035,000	[1]	98,736,000	[1]
General corporate expenses									32,553,000	[2]	23,706,000	[2]	21,636,000	[2]
Interest expense									18,406,658		13,072,605		13,939,149
Other (income) expense, net									(7,022,000)	[3]	(9,113,000)	[3]	(480,000)	[3]
Total expenses									43,938,000		27,666,000		35,095,000
Income before income taxes									93,911,000		94,369,000		63,641,000
Depreciation and amortization									43,305,000		29,363,000		22,595,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									319,173,000		161,981,000		47,147,000
Total assets	953,253,000				694,205,000				953,253,000		694,205,000		606,775,000
Goodwill	278,556,040				171,886,270				278,556,040		171,886,270		121,383,863
Electrical and Industrial Products [Member]
Operations and assets by segment
Net sales									416,106,000		233,555,000		189,192,000
Segment Operating income									45,866,000	[1]	34,228,000	[1]	25,772,000	[1]
Depreciation and amortization									19,959,000		8,587,000		3,317,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									284,514,000		79,513,000		3,161,000
Total assets	540,216,000				260,874,000				540,216,000		260,874,000		143,208,000
Goodwill	183,825,000				75,151,000				183,825,000		75,151,000		43,331,000
Galvanizing Services [Member]
Operations and assets by segment
Net sales									335,618,000		337,039,000		279,920,000
Segment Operating income									91,983,000	[1]	87,807,000	[1]	72,964,000	[1]
Depreciation and amortization									22,009,000		19,501,000		17,783,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									33,281,000		81,604,000		43,298,000
Total assets	378,358,000				370,142,000				378,358,000		370,142,000		309,808,000
Goodwill	94,731,000				96,735,000				94,731,000		96,735,000		78,053,000
Corporate [Member]
Operations and assets by segment
Depreciation and amortization									1,337,000		1,275,000		1,495,000
Expenditures for acquisitions, net of cash, and property, plant and equipment									1,378,000		864,000		688,000
Total assets	$ 34,679,000				$ 63,189,000				$ 34,679,000		$ 63,189,000		$ 153,759,000

[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.