Summary of Marketable Securities by Asset Type (Detail) (USD $) In Thousands	Aug. 31, 2011	May 31, 2011
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	$ 124,912	$ 127,753
Available-for-Sale Securities, gross unrealized gains	18,986	23,408
Available-for-Sale Securities, gross unrealized losses	(3,910)	(1,518)
Available-for-Sale Securities, fair value (net carrying amount)	139,988	149,643
Equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	97,707	98,676
Available-for-Sale Securities, gross unrealized gains	17,551	22,363
Available-for-Sale Securities, gross unrealized losses	(3,882)	(1,437)
Available-for-Sale Securities, fair value (net carrying amount)	111,376	119,602
Equity securities \| Stocks \| Foreign
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	25,356	25,387
Available-for-Sale Securities, gross unrealized gains	13,148	12,162
Available-for-Sale Securities, gross unrealized losses	(811)
Available-for-Sale Securities, fair value (net carrying amount)	37,693	37,549
Equity securities \| Stocks \| Domestic
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	31,972	28,044
Available-for-Sale Securities, gross unrealized gains	2,325	4,222
Available-for-Sale Securities, gross unrealized losses	(2,701)	(417)
Available-for-Sale Securities, fair value (net carrying amount)	31,596	31,849
Equity securities \| Mutual funds \| Foreign
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	14,687	14,680
Available-for-Sale Securities, gross unrealized gains	1,425	3,733
Available-for-Sale Securities, gross unrealized losses	(20)
Available-for-Sale Securities, fair value (net carrying amount)	16,092	18,413
Equity securities \| Mutual funds \| Domestic
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	25,692	30,565
Available-for-Sale Securities, gross unrealized gains	653	2,246
Available-for-Sale Securities, gross unrealized losses	(350)	(1,020)
Available-for-Sale Securities, fair value (net carrying amount)	25,995	31,791
Fixed maturity
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	27,205	29,077
Available-for-Sale Securities, gross unrealized gains	1,435	1,045
Available-for-Sale Securities, gross unrealized losses	(28)	(81)
Available-for-Sale Securities, fair value (net carrying amount)	28,612	30,041
Fixed maturity \| U.S. Treasury and other government
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	24,250	25,916
Available-for-Sale Securities, gross unrealized gains	1,039	643
Available-for-Sale Securities, gross unrealized losses	(19)	(79)
Available-for-Sale Securities, fair value (net carrying amount)	25,270	26,480
Fixed maturity \| Corporate bonds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	2,677	2,729
Available-for-Sale Securities, gross unrealized gains	298	301
Available-for-Sale Securities, gross unrealized losses	(8)	(1)
Available-for-Sale Securities, fair value (net carrying amount)	2,967	3,029
Fixed maturity \| Foreign bonds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	38
Available-for-Sale Securities, gross unrealized losses	(1)
Available-for-Sale Securities, fair value (net carrying amount)	37
Fixed maturity \| Mortgage-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-Sale Securities, amortized cost	240	432
Available-for-Sale Securities, gross unrealized gains	98	101
Available-for-Sale Securities, gross unrealized losses		(1)
Available-for-Sale Securities, fair value (net carrying amount)	$ 338	$ 532

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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