Common Stock Repurchases - Additional Information (Detail) - USD ($)
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3 Months Ended |
9 Months Ended |
11 Months Ended |
35 Months Ended |
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Apr. 30, 2017 |
Apr. 30, 2017 |
Apr. 30, 2017 |
Apr. 30, 2017 |
May 26, 2016 |
Jun. 02, 2014 |
| 2016 Repurchase program |
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| Stockholders Equity Note [Line Items] |
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| Repurchase of common stock (in shares) |
8,090
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8,090
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8,090
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| Repurchase of common stock |
$ 600,000
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$ 600,000
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$ 600,000
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| Average purchase price of common stock |
$ 71.46
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$ 71.46
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$ 71.46
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| 2016 Repurchase program | Maximum |
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| Stockholders Equity Note [Line Items] |
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| Amount authorized for repurchase of Company's common stock |
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$ 15,000,000
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| 2014 repurchase program |
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| Stockholders Equity Note [Line Items] |
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| Repurchase of common stock (in shares) |
13,578
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13,578
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380,771
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| Repurchase of common stock |
$ 1,000,000
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$ 1,000,000
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$ 30,000,000
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| Average purchase price of common stock |
$ 74.08
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$ 74.08
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$ 78.76
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| 2014 repurchase program | Maximum |
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| Stockholders Equity Note [Line Items] |
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| Amount authorized for repurchase of Company's common stock |
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$ 30,000,000
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| Repurchased stock of unused capacity |
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$ 1,000,000
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