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Quarterly Financial Information (Parenthetical) (Detail) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 2018 | Jul. 31, 2016 | Apr. 30, 2018
Quarterly Financial Information [Line Items] |  |  |
Income tax benefit by effect of tax reform | $ 9.4 |  | $ 8.7
ASU 2016-09 |  |  |
Quarterly Financial Information [Line Items] |  |  |
Net income increased |  | $ 2.6 |
Net income per basic share increased |  | $ 0.05 |
Net income per diluted share increased |  | $ 0.05 |

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- Definition Tax cuts and jobs act of 2017, change in tax rate, income tax expense (benefit). + References No definition available. + Details
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