Summary of Available-for-Sale Marketable Securities by Asset Type (Detail) - USD ($) $ in Thousands	Feb. 28, 2019	May 31, 2018
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	$ 24,064	$ 23,994
Available-for-Sale Debt Securities, Gross Unrealized Gains	103	82
Available-for-Sale Debt Securities, Gross Unrealized Losses	(383)	(560)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	23,784	23,516
Equity Securities, Amortized Cost		145,956
Equity Securities, Gross Unrealized Gains		2,566
Equity Securities, Gross Unrealized Losses		(3,967)
Equity Securities, Fair Value (Net Carrying Amount)	89,200	144,555
Total Securities, Amortized Cost		169,950
Total Securities, Gross Unrealized Gains		2,648
Total Securities, Gross Unrealized Losses		(4,527)
Total Securities, Fair Value (Net Carrying Amount)		$ 168,071
Foreign
Debt Securities, Available-for-sale [Line Items]
Equity Securities, FV-NI, Type [Extensible List]		us-gaap:MutualFundMember
Equity Securities, Amortized Cost		$ 46,123
Equity Securities, Gross Unrealized Gains		1,839
Equity Securities, Gross Unrealized Losses		(1,197)
Equity Securities, Fair Value (Net Carrying Amount)		$ 46,765
Domestic
Debt Securities, Available-for-sale [Line Items]
Equity Securities, FV-NI, Type [Extensible List]		us-gaap:MutualFundMember
Equity Securities, Amortized Cost		$ 99,833
Equity Securities, Gross Unrealized Gains		727
Equity Securities, Gross Unrealized Losses		(2,770)
Equity Securities, Fair Value (Net Carrying Amount)		97,790
U.S. Treasury and other government
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	23,642	23,562
Available-for-Sale Debt Securities, Gross Unrealized Gains	68	39
Available-for-Sale Debt Securities, Gross Unrealized Losses	(375)	(552)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	23,335	23,049
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	422	432
Available-for-Sale Debt Securities, Gross Unrealized Gains	35	43
Available-for-Sale Debt Securities, Gross Unrealized Losses	(8)	(8)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	$ 449	$ 467

Equity securities and available for sale debt securities.

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Equity securities and available for sale debt securities accumulated gross unrealized gain before tax.

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Equity securities fair value accumulated gross unrealized gain before tax.

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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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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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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