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Marketable Securities - Marketable Securities (Detail) - USD ($)
$ in Thousands
Nov. 30, 2015
May. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Amortized cost $ 1,800 $ 1,825
Gross Unrealized Gains 0 0
Gross Unrealized Losses (161) (136)
Fair Value 1,639 1,689
U.S. Government Agency Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized cost 1,800 1,825
Gross Unrealized Gains 0 0
Gross Unrealized Losses (161) (136)
Fair Value $ 1,639 $ 1,689