Net Carrying Values of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Nov. 30, 2018	May 31, 2018
Available-for-Sale Securities, amortized cost
Less than one year, amortized cost	$ 7,897
One year through five years, amortized cost	11,576
Six years through ten years, amortized cost	3,294
After ten years, amortized cost	936
Available-for-Sale Debt Securities, Amortized Cost	23,703	$ 23,994
Available-for-Sale Securities, fair value
Less than one year, fair value	7,841
One year through five years, fair value	11,282
Six years through ten years, fair value	3,152
After ten years, fair value	948
Marketable debt securities, carrying value	$ 23,223	$ 23,516

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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