Summary of Marketable Securities by Asset Type (Detail) - USD ($) $ in Thousands	Aug. 31, 2015	May. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	$ 147,533	$ 149,864
Available-for-Sale Securities, Gross Unrealized Gains	4,207	8,721
Available-for-Sale Securities, Gross Unrealized Losses	(9,777)	(3,815)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	141,963	154,770
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	125,037	127,189
Available-for-Sale Securities, Gross Unrealized Gains	3,918	8,330
Available-for-Sale Securities, Gross Unrealized Losses	(9,598)	(3,653)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	119,357	131,866
Equity securities \| Stocks \| Foreign
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	4,201	3,722
Available-for-Sale Securities, Gross Unrealized Gains	193	339
Available-for-Sale Securities, Gross Unrealized Losses	(415)	(85)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	3,979	3,976
Equity securities \| Stocks \| Domestic
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	31,465	34,368
Available-for-Sale Securities, Gross Unrealized Gains	2,757	5,649
Available-for-Sale Securities, Gross Unrealized Losses	(1,004)	(559)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	33,218	39,458
Equity securities \| Mutual funds \| Foreign
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	32,681	32,657
Available-for-Sale Securities, Gross Unrealized Gains	959	2,114
Available-for-Sale Securities, Gross Unrealized Losses	(2,702)	(230)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	30,938	34,541
Equity securities \| Mutual funds \| Domestic
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	56,690	56,442
Available-for-Sale Securities, Gross Unrealized Gains	9	228
Available-for-Sale Securities, Gross Unrealized Losses	(5,477)	(2,779)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	51,222	53,891
Fixed maturity
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	22,496	22,675
Available-for-Sale Securities, Gross Unrealized Gains	289	391
Available-for-Sale Securities, Gross Unrealized Losses	(179)	(162)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	22,606	22,904
Fixed maturity \| U.S. Treasury and other government
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	21,187	21,340
Available-for-Sale Securities, Gross Unrealized Gains	111	171
Available-for-Sale Securities, Gross Unrealized Losses	(179)	(162)
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	21,119	21,349
Fixed maturity \| Foreign bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	36	36
Available-for-Sale Securities, Gross Unrealized Gains	2	2
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	38	38
Fixed maturity \| Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	59	81
Available-for-Sale Securities, Gross Unrealized Gains	37	47
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	96	128
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	1,214	1,218
Available-for-Sale Securities, Gross Unrealized Gains	139	171
Available-for-Sale Securities, Fair Value (Net Carrying Amount)	$ 1,353	$ 1,389

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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