Investments in Unconsolidated Affiliates - Schedule of Combined Financial Information for Unconsolidated Affiliates (Detail) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017	May 31, 2018
Equity Method Investments And Joint Ventures [Abstract]
Cash	$ 43,004		$ 52,812
Other current assets	717,270		590,578
Current assets for discontinued operations	37,474		37,640
Noncurrent assets	365,396		358,927
Total assets	1,163,144		1,039,957
Current liabilities	244,831		166,493
Current liabilities for discontinued operations	8,243		7,142
Short-term borrowings	36,215		26,599
Current maturities of long-term debt	43,131		23,243
Long-term debt	261,348		259,588
Other noncurrent liabilities	17,541		17,536
Equity	551,835		539,356
Total liabilities and equity	1,163,144		$ 1,039,957
Net sales	498,545	$ 442,624
Gross margin	103,812	86,235
Operating income	72,376	57,163
Depreciation and amortization	6,477	7,193
Interest expense	2,925	2,492
Income tax expense	4,525	1,348
Net earnings from continuing operations	64,894	51,061
Net earnings from discontinued operations	1,684	1,413
Net earnings	$ 66,578	$ 52,474