Stockholders' Equity	12 Months Ended
Sep. 30, 2019
Equity [Abstract]
Stockholders' Equity	NOTE 6. STOCKHOLDERS’ EQUITY At September 30, 2019, the Company had a total of 150,000,000 shares of capital stock authorized for issuance, consisting of 145,000,000 shares of Common Stock, par value $0.001 per share, and 5,000,000 shares of Preferred Stock, par value $0.001 per share. At September 30, 2019, 95,506,271 shares of Common Stock were outstanding. At September 30, 2019, 7,177,796 shares of Common Stock were reserved for issuance upon exercise of options and vesting of restricted stock units granted or available for grant under Arrowhead’s 2004 Equity Incentive Plan and 2013 Incentive Plan, as well as for inducement grants made to new employees. In October 2018 the Company sold 3,260,869 shares of Common Stock to JJDC at a price of $23.00 per share as part of the JJDC Stock Purchase Agreement discussed further in Note 2 above. The Company received proceeds of $75.0 million. The portion of these proceeds that were deemed to be a premium were recorded as deferred revenue as discussed further in Note 2 above.

Stockholders' Equity

12 Months Ended

Sep. 30, 2019

NOTE 6. STOCKHOLDERS’ EQUITY

At September 30, 2019, the Company had a total of 150,000,000 shares of capital stock authorized for issuance, consisting of 145,000,000 shares of Common Stock, par value $0.001 per share, and 5,000,000 shares of Preferred Stock, par value $0.001 per share.

At September 30, 2019, 95,506,271 shares of Common Stock were outstanding. At September 30, 2019, 7,177,796 shares of Common Stock were reserved for issuance upon exercise of options and vesting of restricted stock units granted or available for grant under Arrowhead’s 2004 Equity Incentive Plan and 2013 Incentive Plan, as well as for inducement grants made to new employees.

In October 2018 the Company sold 3,260,869 shares of Common Stock to JJDC at a price of $23.00 per share as part of the JJDC Stock Purchase Agreement discussed further in Note 2 above. The Company received proceeds of $75.0 million. The portion of these proceeds that were deemed to be a premium were recorded as deferred revenue as discussed further in Note 2 above.