Goodwill and Other Long-Lived Assets - Summary of Changes in Carrying Amount of Goodwill (Detail) (Parenthetical) $ in Thousands	12 Months Ended
	May 31, 2018 USD ($)
Goodwill [Line Items]
Impairment losses	$ 9,666	[1]
Oil and Gas Equipment
Goodwill [Line Items]
Impairment losses	4,015
WEI Reporting Unit
Goodwill [Line Items]
Impairment losses	$ 5,651
Sale of stake, percentage	65.00%

[1] Fiscal 2018 impairment charges included $4,015,000 of goodwill allocated to oil & gas equipment assets prior to their disposal on July 31, 2018 and $5,651,000 related to the sale of a 65% stake in WEI on March 31, 2018.