Income Taxes (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Income Taxes [Line Items]
Operating loss carryforwards for state income tax purposes	$ 80,756
Gross unrecognized tax benefits	7,538	6,148	5,482
Unrecognized tax benefits impacting effective tax rate if recognized	4,900
Net increase of unrecognized tax benefits	1,390
Unrecognized tax benefits, accrued interest and penalties	249	245
Increase (decrease) in tax expense due to net interest and penalties	4	(5)
Best estimate for reasonably change in amount of gross unrecognized tax benefits is a decrease during 12 months	$ 1,370
Minimum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration date	2017
Maximum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration date	2032

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Increase In Tax Expense Due To Net Interest And Penalties

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- Definition

The sum of domestic, foreign and state and local operating loss carryforwards, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 48

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The expiration date of each operating loss carryforward included in total operating loss carryforwards, or the applicable range of such expiration dates.

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The estimated lower bound of the reasonably possible change in the total amount of the unrecognized tax benefit (that will significantly increase or decrease within twelve months of the balance sheet date) for a tax position taken.

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- Definition

The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

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- Definition

This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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The net amount of all increases and decreases in unrecognized tax benefits for the period.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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