Other Financial Instruments and Fair Value Measurements (Textuals) (USD $)	3 Months Ended	12 Months Ended
Jul. 31, 2011	Apr. 30, 2011	Apr. 30, 2010	Apr. 30, 2009
Other Financial Instruments and Fair Value Measurements (Details) [Abstract]
Marketable Securities Sold	$ 10,000,000
Sales and maturities of marketable securities	18,600,000	57,100,000	13,519,000	3,013,000
Company's Municipal bond mature in 2012	1,463,000
Company's Municipal bond mature in 2013	3,392,000
Company's Municipal bond mature in 2014	741,000
Company's Municipal bond mature in 2015	2,764,000
Company's Municipal bond mature in 2016	$ 12,113,000

The cash inflow associated maturities (principal being due), prepayments and calls (requests of early payments) on securities not classified as either held-to-maturity securities or trading securities which are classified as available-for-sale securities.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 16

-Subparagraph a

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Chapter V

-Section 563c.102

-Subsection III

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 15

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 16

-Subparagraph b

Name:	us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration