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Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended
--- | ---
May 31, 2017 | May 31, 2016 | May 31, 2015
Shareholder Rights [Line Items] |  |  |
Authorization of stock repurchase program | Jan. 08, 2008 |  |
Shares repurchased | 0 | 800,000 | 595,106
Shares repurchased, value |  | $ 35,098 | $ 27,588
Repurchase of common stock price per shares |  | $ 43.88 | $ 46.36
Minimum |  |  |
Shareholder Rights [Line Items] |  |  |
Shares authorized to be repurchased, per year | 1,000,000 | 1,000,000 | 1,000,000
Maximum |  |  |
Shareholder Rights [Line Items] |  |  |
Shares authorized to be repurchased, per year | 2,000,000 | 2,000,000 | 2,000,000

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- Definition Number of shares that have been repurchased during the period and are being held in treasury. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 + Details
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