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Stock-Based Compensation - Summary of Activity under Company's Stock Option Plans (Detail) (USD $) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2014 | Jul. 31, 2014 | Jan. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |  |  |
Shares, Outstanding, Beginning balance |  | 916,150 |
Shares, Granted | 0 | 180,500 |
Shares, Exercised |  | (153,800) |
Shares, Outstanding, Ending balance | 942,850 | 942,850 | 916,150
Shares, Exercisable | 540,350 | 540,350 | 613,150
Weighted Average Exercise Price, Outstanding, Beginning balance |  | $ 17.36 |
Weighted Average Exercise Price, Granted |  | $ 27.09 |
Weighted Average Exercise Price, Exercised |  | $ 14.84 |
Weighted Average Exercise Price, Outstanding, Ending balance | $ 19.63 | $ 19.63 | $ 17.36
Weighted Average Exercise Price, Exercisable | $ 15.67 | $ 15.67 | $ 15.40
Weighted Average Remaining Contract Term, Granted |  | 0 years |
Weighted Average Remaining Contract Term, Exercised |  | 0 years |
Weighted Average Remaining Contract Term, Outstanding |  | 6 years 7 months 24 days | 6 years 15 days
Weighted Average Remaining Contract Term, Exercisable |  | 5 years 11 months 1 day | 5 years 1 month 2 days
Weighted Average Fair Value, Granted |  | $ 0 |
Weighted Average Fair Value, Exercised |  | $ 0 |
Weighted Average Fair Value, Outstanding, Beginning balance | $ 5.72 | $ 5.72 | $ 5.58
Weighted Average Fair Value, Exercisable | $ 5.91 | $ 5.91 | $ 6.15

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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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