Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted and outstanding to purchase	1,910,794	729,096	812,334
Options granted	1,229,500	20,000
Stock-based compensation expense	$ 1,241,404	$ 1,376,921
Stock-based compensation expense in discontinued operations	0	27,519
Fair value of the options granted	4,091,117	93,004
Intrinsic value of the options exercised	0	3,666
Arrowhead [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	3,738,217
Weighted average period to recognize pre-tax compensation expense	3 years 1 month 6 days
Calando Pharmaceuticals, Inc. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of the options granted	33,690	33,870
Pre-tax compensation expense	$ 63,250
Weighted average period to recognize pre-tax compensation expense	2 years 7 months 6 days
2000 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserve for issuance	153,200
Options granted and outstanding to purchase	153,200
2004 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserve for issuance	1,965,860
Options granted and outstanding to purchase	1,767,894
Options granted	988,300
Options granted outside of Equity Incentive plans	251,200

Allocated share based compensation expense related to discontinued operations.

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- Definition

Pre tax compensation expense.

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- Definition

Share based compensation arrangement by share based payment award options grants in period fair value.

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- Definition

Weighted average period to recognize pre-tax compensation expense.

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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

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph g(1)

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 64

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-Name Accounting Standards Codification

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- Definition

Aggregate number of common shares reserved for future issuance.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 4

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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-Subparagraph (SX 210.5-02.29)

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- Definition

Net number of non-option equity instruments granted to participants.

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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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- Definition

Gross number of share options (or share units) granted during the period.

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- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

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