Financial Results of Three Largest Affiliated Companies (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Investments in and Advances to Affiliates [Line Items]
Net sales	$ 1,492,802	$ 1,753,734	$ 1,685,743
Gross margin	312,620	332,849	314,393
Operating income	213,932	230,924	221,013
Depreciation and amortization	36,958	40,712	34,153
Interest expense	9,222	8,894	6,047
Income tax expense	9,854	6,856	15,114
Net earnings	196,131	216,002	201,733
WAVE
Investments in and Advances to Affiliates [Line Items]
Net sales	382,821	370,702	364,530
Gross margin	177,935	167,924	155,246
Operating income	144,167	137,202	127,305
Depreciation and amortization	4,916	3,919	4,142
Interest expense	6,464	6,280	3,427
Income tax expense	3,606	2,451	2,789
Net earnings	134,019	128,614	121,261
ClarkDietrich
Investments in and Advances to Affiliates [Line Items]
Net sales	549,267	547,971	564,624
Gross margin	73,803	75,580	61,703
Operating income	27,918	35,024	27,094
Depreciation and amortization	16,253	18,173	14,271
Interest expense	103	3	3
Net earnings	27,837	35,005	27,203
TWB
Investments in and Advances to Affiliates [Line Items]
Net sales	54,003	344,065	312,943
Gross margin	6,109	41,116	40,098
Operating income	4,273	28,241	28,141
Depreciation and amortization	880	5,123	3,259
Income tax expense	478	1,218	5,458
Net earnings	4,023	27,931	22,952
Other Affiliates
Investments in and Advances to Affiliates [Line Items]
Net sales	506,711	490,996	443,646
Gross margin	54,773	48,229	57,346
Operating income	37,574	30,457	38,473
Depreciation and amortization	14,909	13,497	12,481
Interest expense	2,655	2,611	2,617
Income tax expense	5,770	3,187	6,867
Net earnings	$ 30,252	$ 24,452	$ 30,317