Summary of Marketable Securities by Asset Type (Detail) - USD ($) $ in Thousands	Aug. 31, 2018	May 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	$ 172,881	$ 169,950
Available-for-Sale Securities, Gross Unrealized Gains	6,132	2,648
Available-for-Sale Securities, Gross Unrealized Losses	(4,975)	(4,527)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	174,038	168,071
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	147,980	145,956
Available-for-Sale Securities, Gross Unrealized Gains	6,051	2,566
Available-for-Sale Securities, Gross Unrealized Losses	(4,471)	(3,967)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	149,560	144,555
Equity securities \| Mutual funds \| Foreign
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	47,736	46,123
Available-for-Sale Securities, Gross Unrealized Gains	1,241	1,839
Available-for-Sale Securities, Gross Unrealized Losses	(2,163)	(1,197)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	46,814	46,765
Equity securities \| Mutual funds \| Domestic
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	100,244	99,833
Available-for-Sale Securities, Gross Unrealized Gains	4,810	727
Available-for-Sale Securities, Gross Unrealized Losses	(2,308)	(2,770)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	102,746	97,790
Fixed maturity
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	24,901	23,994
Available-for-Sale Securities, Gross Unrealized Gains	81	82
Available-for-Sale Securities, Gross Unrealized Losses	(504)	(560)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	24,478	23,516
Fixed maturity \| U.S. Treasury and other government
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	24,479	23,562
Available-for-Sale Securities, Gross Unrealized Gains	42	39
Available-for-Sale Securities, Gross Unrealized Losses	(494)	(552)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	24,027	23,049
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	422	432
Available-for-Sale Securities, Gross Unrealized Gains	39	43
Available-for-Sale Securities, Gross Unrealized Losses	(10)	(8)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	$ 451	$ 467

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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