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Shareholders' Equity - Additional Information (Detail) |  | 12 Months Ended
--- | --- | ---
Jul. 11, 2016 | Sep. 30, 2017
Class of Stock [Line Items] |  |
Stock split ratio |  | 1.5
Common Stock [Member] |  |
Class of Stock [Line Items] |  |
Right of holders to elect company's board of directors |  | 25.00%
Class B Stock [Member] |  |
Class of Stock [Line Items] |  |
Right of holders to elect company's board of directors |  | 75.00%
Common and Class B Stock [Member] |  |
Class of Stock [Line Items] |  |
Stock split ratio | 1.5 |
Stock dividend percentage | 50.00% |
Stock split ratio description |  | On July 11, 2016, the Company's Board of Directors approved a three-for-two split of the Company's common and Class B stock to be effected in the form of a 50% stock dividend. As a result, shareholders received one additional share of common or Class B stock for every two shares they held of the respective class of stock as of the record date.

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- Definition Description of the stock split arrangement. Also provide the retroactive effect given by a stock split that occurs after the balance date but before the release of financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 4.C) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770 + Details
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