Fair Value Measurements (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
ASSETS
Supplemental executive retirement plan	$ 3,510	$ 3,418
Fair Value, Measurements, Recurring
ASSETS
Total assets measured at fair value	3,635	3,427
Fair Value, Measurements, Recurring | Money market funds | Supplemental executive retirement plan
ASSETS
Supplemental executive retirement plan	150	323
Fair Value, Measurements, Recurring | Mutual funds | Supplemental executive retirement plan
ASSETS
Supplemental executive retirement plan	3,360	3,095
Fair Value, Measurements, Recurring | Foreign exchange forward contracts
ASSETS
Foreign exchange forward contracts	125	9
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring
ASSETS
Total assets measured at fair value	3,510	3,418
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Money market funds | Supplemental executive retirement plan
ASSETS
Supplemental executive retirement plan	150	323
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Mutual funds | Supplemental executive retirement plan
ASSETS
Supplemental executive retirement plan	3,360	3,095
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
ASSETS
Total assets measured at fair value	125	9
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Foreign exchange forward contracts
ASSETS
Foreign exchange forward contracts	$ 125	$ 9