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The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.

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Tax year being audited in the income tax examination, in CCYY format.

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Tax year that remains open to examination under enacted tax laws, in CCYY format.

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Amount of (increase) decrease reasonably possible in the estimated lower bound of the unrecognized tax benefit for a tax position taken or expected to be taken.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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

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Unrecognized Tax Benefits (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Apr. 30, 2014
Income Tax Contingency
Unrecognized tax benefits	$ 10,307us-gaap_UnrecognizedTaxBenefits		$ 9,224us-gaap_UnrecognizedTaxBenefits
Unrecognized tax benefits that would impact effective tax rate	6,736
Accrued interest and penalties related to unrecognized tax benefits	226		402
Interest and penalties included in income tax expense	(176)	(146)
Expected decrease in unrecognized tax benefits	$ 2,352
Federal Tax Authority \| Earliest Tax Year
Income Tax Contingency
Tax years open for examination	2011
State Tax Authority \| Earliest Tax Year
Income Tax Contingency
Tax years open for examination	2009
Illinois \| Tax Year 2011
Income Tax Contingency
Year under examination	2011
Illinois \| Tax Year 2012
Income Tax Contingency
Year under examination	2012