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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Investments (Contractual Maturities Of AFS Debt Securities At Varying Dates Over The Next 30 Years) (Details) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013	Apr. 30, 2013	Jul. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of AFS debt securities, Cost Basis, Total	$ 493,565	$ 480,628	$ 375,545
Contractual maturities of AFS debt securities, Fair Value, Total	487,033	486,876	381,791
Two to Five Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of AFS debt securities, Cost Basis, Total	4,164
Contractual maturities of AFS debt securities, Fair Value, Total	4,430
Beyond [Member]
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of AFS debt securities, Cost Basis, Total	489,401
Contractual maturities of AFS debt securities, Fair Value, Total	$ 482,603