Fair Value - Additional Information (Detail) - USD ($)	Nov. 30, 2018	May 31, 2018
Long-term Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt at fair value including current maturities	$ 737,341,000	$ 757,069,000
Long-term debt at carrying amount including current maturities	749,779,000	750,368,000
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	0	$ 30,000,000
Liabilities measured at fair value on non-recurring basis	$ 0