Savings Plan, Employee Stock Ownership Plan and Retirement Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Postemployment Benefits Disclosure [Line Items]
Requisite service period to become eligible to participate in 401(k)	90 days
Minimum requisite service period for additional discretionary contributions	3 years
Contributions to Retirement Plan	$ 554	$ 848	$ 784
Other assets	16,597	13,743
Supplemental Executive Retirement Plan [SERP]
Postemployment Benefits Disclosure [Line Items]
Contributions to Retirement Plan	14	22	$ 25
Accrued Expense	3,089	3,521
Other assets	$ 3,089	$ 3,521