Investments (Amortized Cost And Fair Value Of Securities Available-For-Sale) (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Apr. 30, 2014	Jan. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 361,356	$ 424,817	$ 453,231
Gross Unrealized Gains	15,701	3,007	3,442
Gross Unrealized Losses	(1,329)	0	(12,903)
Fair Value	375,728us-gaap_AvailableForSaleSecurities	427,824us-gaap_AvailableForSaleSecurities	443,770us-gaap_AvailableForSaleSecurities
Long-Term \| Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	352,179	420,697	449,097
Gross Unrealized Gains	15,566	2,798	3,201
Gross Unrealized Losses	0	0	(12,903)
Fair Value	367,745	423,495	439,395
Long-Term \| Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,077	4,120	4,134
Gross Unrealized Gains	135	209	241
Gross Unrealized Losses	(17)	0	0
Fair Value	4,195	4,329	4,375
Long-Term \| Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(1,312)
Fair Value	3,688
Long-Term \| US Treasury Bill Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	100
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 100

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

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

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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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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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

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

-Publisher FASB

-Name Accounting Standards Codification

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

-Publisher FASB

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