Schedule of Combined Financial Information for Unconsolidated Affiliates (Detail) - Unconsolidated Affiliates - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	May 31, 2017
Investments in and Advances to Affiliates [Line Items]
Cash	$ 40,943		$ 55,541
Other current assets	591,345		559,021
Noncurrent assets	366,877		361,106
Total assets	999,165		975,668
Current liabilities	157,932		156,947
Short-term borrowings	11,063		8,172
Current maturities of long-term debt	4,367		5,827
Long-term debt	268,867		268,711
Other noncurrent liabilities	24,816		21,380
Equity	532,120		514,631
Total liabilities and equity	999,165		$ 975,668
Net sales	442,624	$ 417,115
Gross margin	86,235	124,197
Operating income	57,163	94,397
Depreciation and amortization	7,193	6,820
Interest expense	2,492	2,148
Income tax expense	1,348	7,518
Net earnings	$ 52,474	$ 86,067