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Stock-Based Compensation, Director Stock Awards (Details) - Director Stock Plan [Member] - Class A Common Stock [Member] - Non-Employee Directors [Member] - shares | 12 Months Ended
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Apr. 30, 2018 | Apr. 30, 2017 | Apr. 30, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] |  |  |
Value of annual award as percentage of annual director retainer fee based on stock price on date of grant | 100.00% |  |
Shares awarded under the plan (in shares) | 19,900 | 20,243 | 19,559

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- Definition The value of the annual award of Class A Common Stock received by each non-employee director as a percentage of the annual director fee, based on the stock price on the date of grant. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Number of shares issued pursuant to the terms of a deferred compensation arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Details
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