Net Sales by Product Category Net of Intercompany Activity (Detail) (USD $) In Thousands, unless otherwise specified	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
Segment Reporting Information [Line Items]
Net Sales	$ 25,859	$ 30,387	$ 29,927	$ 34,834	$ 32,272	$ 34,009	$ 34,417	$ 36,036	$ 121,007	$ 136,734	$ 137,624
Percentage of net sales									100.00%	100.00%	100.00%
Acoustical
Segment Reporting Information [Line Items]
Net Sales									73,800	68,300	73,100
Percentage of net sales									61.00%	50.00%	53.00%
Coated
Segment Reporting Information [Line Items]
Net Sales									$ 47,200	$ 68,400	$ 64,500
Percentage of net sales									39.00%	50.00%	47.00%