Summary of Available-for-Sale Securities in Unrealized Loss Position and Included in Accumulated Other Comprehensive (Loss), Aggregated by Length of Time Investments (Detail) - USD ($) $ in Thousands	Aug. 31, 2019	May 31, 2019
Investments Debt And Equity Securities [Abstract]
Total investments with unrealized losses, fair value	$ 6,802	$ 11,508
Unrealized losses with a loss position for less than 12 months, fair value	283	806
Unrealized losses with a loss position for more than 12 months, fair value	6,519	10,702
Total investments with unrealized losses, gross unrealized losses	(124)	(311)
Unrealized losses with a loss position for less than 12 months, gross unrealized losses		(2)
Unrealized losses with a loss position for more than 12 months, gross unrealized losses	$ (124)	$ (309)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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