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Stock-Based Compensation - Additional Information (Detail) (USD $) | 12 Months Ended
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Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Shares reserve for issuance | 467,322 |  |
Options and restricted stock units outstanding | 3,850,840 | 3,419,285 | 1,910,794
Options and restricted stock units granted | 1,039,000 | 1,509,166 |
Dividend yield | 0.00% | 0.00% | 0.00%
Arrowhead |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Unrecognized pre-tax compensation expense | $ 10,517,380 |  |
Weighted average period to recognize pre-tax compensation expense | 3 years 1 month 6 days |  |
Restricted Stock Units (RSUs) |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Units granted outside of Equity Incentive plans | 40,000 |  |
Stock-based compensation expense | 2,551,397 | 0 | 0
Number of restricted stock units issued under 2013 incentive plan | 510,000 | 0 | 0
Number of restricted stock units outstanding, granted | 510,000 |  |
Restricted Stock Units (RSUs) | Arrowhead |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Unrecognized pre-tax compensation expense | 4,913,516 |  |
Weighted average period to recognize pre-tax compensation expense | 1 year 6 months |  |
Stock Options |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Units granted outside of Equity Incentive plans | 185,000 |  |
Stock-based compensation expense | 3,144,776 | 1,536,271 | 1,241,404
Fair value of the options granted | 9,267,048 | 2,843,575 | 4,091,117
Intrinsic value of the options exercised | $ 4,360,850 | $ 554 | $ 0
Dividend yield | 0.00% |  |
2000 Stock Option Plan |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Shares reserve for issuance | 38,000 |  |
2000 Stock Option Plan | Restricted Stock |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Options and restricted stock units outstanding | 38,000 |  |
2004 Equity Incentive Plan |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Shares reserve for issuance | 2,659,852 |  |
Options and restricted stock units granted | 0 |  |
2004 Equity Incentive Plan | Restricted Stock |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Options and restricted stock units outstanding | 2,563,518 |  |
2013 Incentive Plan |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Shares reserve for issuance | 4,000,000 |  |
Options and restricted stock units granted | 1,324,000 |  |
2013 Incentive Plan | Restricted Stock |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Options and restricted stock units outstanding | 1,292,000 |  |
2013 Incentive Plan | Restricted Stock Units (RSUs) |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Number of restricted stock units outstanding, granted | 470,000 |  |

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- Definition Share based compensation arrangement by share based payment award options grants in period fair value. + References No definition available. + Details
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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- Definition Aggregate number of common shares reserved for future issuance. + 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 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, 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 (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested options awarded to employees as compensation. + References No definition available. + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + 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 (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + 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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