Schedule of Combined Financial Information for Unconsolidated Affiliates (Detail) - Unconsolidated Affiliates - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016	May 31, 2017
Investments in and Advances to Affiliates [Line Items]
Cash	$ 50,389		$ 50,389		$ 55,541
Other current assets	553,970		553,970		559,021
Noncurrent assets	371,328		371,328		361,106
Total assets	975,687		975,687		975,668
Current liabilities	139,168		139,168		156,947
Short-term borrowings	16,539		16,539		8,172
Current maturities of long-term debt	5,118		5,118		5,827
Long-term debt	266,036		266,036		268,711
Other noncurrent liabilities	21,637		21,637		21,380
Equity	527,189		527,189		514,631
Total liabilities and equity	975,687		975,687		$ 975,668
Net sales	412,617	$ 387,192	855,241	$ 804,307
Gross margin	71,122	96,541	157,357	220,738
Operating income	34,604	67,365	91,767	161,762
Depreciation and amortization	5,935	6,973	13,128	13,793
Interest expense	2,461	2,151	4,953	4,299
Income tax expense	1,816	3,545	3,164	11,063
Net earnings	$ 30,190	$ 63,444	$ 82,664	$ 149,511