Segment Operations (Financial Information For Reportable Segments) (Details) (USD $) In Thousands	3 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	May 31, 2011
Net sales	$ 602,387	$ 616,805
Operating income (loss)	21,183	21,072
Pre-tax restructuring and other expense	1,703	1,064
Joint venture transactions	3,215
Total assets	1,645,421		1,667,249
Steel Processing [Member]
Net sales	408,174	354,865
Operating income (loss)	16,276	16,617
Pre-tax restructuring and other expense		(102)
Total assets	713,919		742,838
Pressure Cylinders [Member]
Net sales	168,829	136,074
Operating income (loss)	11,915	9,554
Total assets	515,998		481,361
Metal Framing [Member]
Net sales	3,145	84,504
Operating income (loss)	(3,688)	(3,930)
Pre-tax restructuring and other expense		920
Joint venture transactions	3,215
Total assets	28,842		37,069
Other [Member]
Net sales	22,239	41,362
Pre-tax restructuring and other expense	1,703	246
Total assets	$ 386,662		$ 405,981