Investments in Unconsolidated Affiliates - Schedule of Combined Financial Information for Unconsolidated Affiliates (Detail) - USD ($) $ in Thousands	May 31, 2018	May 31, 2017
Equity Method Investments And Joint Ventures [Abstract]
Cash	$ 52,812	$ 55,541
Other current assets	590,578	541,746
Current assets for discontinued operations	37,640	17,275
Noncurrent assets	358,927	342,938
Noncurrent assets for discontinued operations		18,168
Total assets	1,039,957	975,668
Current liabilities	166,493	148,056
Current liabilities for discontinued operations	7,142	8,891
Short-term borrowings	26,599	8,172
Current maturities of long-term debt	23,243	5,827
Long-term debt	259,588	268,711
Other noncurrent liabilities	17,536	20,890
Noncurrent liabilities for discontinued operations		490
Equity	539,356	514,631
Total liabilities and equity	$ 1,039,957	$ 975,668