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Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) | Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
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Earnings Per Share [Abstract] |  |  |
Interest rate on convertible senior notes | 0.50% | 0.50% | 0.50%

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- References No definition available. + Details
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