Net Carrying Values of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Aug. 31, 2019	May 31, 2019
Available-for-Sale Securities, Amortized Cost
Less than one year, amortized cost	$ 9,370
One year through five years, amortized cost	10,161
Six years through ten years, amortized cost	4,548
After ten years, amortized cost	1,175
Available-for-Sale Debt Securities, Amortized Cost	25,254	$ 24,905
Available-for-Sale Securities, Fair Value
Less than one year, fair value	9,338
One year through five years, fair value	10,242
Six years through ten years, fair value	4,816
After ten years, fair value	1,337
Available-for-sale debt securities, fair value	$ 25,733	$ 25,009

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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