Subsequent Events	3 Months Ended
Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	NOTE 9. SUBSEQUENT EVENTS On January 8, 2016, the Company entered into a new lease for a Madison, Wisconsin research facility. The 10-year office building lease between the Company’s subsidiary, Arrowhead Madison Inc. and University Research Park, Incorporated is for approximately 60,000 square feet of office and laboratory space located at 502 South Rosa Road, Madison, Wisconsin, and this lease will replace the Company’s current research facility lease also with University Research Park, Incorporated for property located at 465 Science Drive, Madison Wisconsin. The increased capacity of this new facility compared to the Company’s current research facilities will accommodate increased research and development personnel for the Company’s expanding pipeline of current and future drug candidates. The initial term of the lease commenced on January 1, 2016 with expected occupancy in late 2016, after certain leasehold improvements have been completed. The lease payments, which begin on October 1, 2016, will be approximately $15.4 million over the initial 10-year term. We also estimate payments for the Company’s pro rata share of certain real estate taxes, operating expenses and common area maintenance expenses to be approximately $0.9 million for the first year of the lease, and these payments will continue throughout the initial 10-year term. The Company expects to pay approximately $7.3 million for leasehold improvements, net of tenant improvement allowances. Pursuant to the lease, within six months of the expiration of the initial 10-year term, the Company has the option to extend the lease for up to two additional five-year terms, with certain annual increases in base rent. Additionally, on January 8, 2016 and in conjunction with signing the new lease agreement as discussed above, the Company entered into an amendment to the Company’s current research facility lease for property located at 465 Science Drive Suite C, Madison, Wisconsin with University Research Park, Incorporated that provides for an early termination of such lease effective on October 31, 2016.

NOTE 9. SUBSEQUENT EVENTS

On January 8, 2016, the Company entered into a new lease for a Madison, Wisconsin research facility. The 10-year office building lease between the Company’s subsidiary, Arrowhead Madison Inc. and University Research Park, Incorporated is for approximately 60,000 square feet of office and laboratory space located at 502 South Rosa Road, Madison, Wisconsin, and this lease will replace the Company’s current research facility lease also with University Research Park, Incorporated for property located at 465 Science Drive, Madison Wisconsin. The increased capacity of this new facility compared to the Company’s current research facilities will accommodate increased research and development personnel for the Company’s expanding pipeline of current and future drug candidates.

The initial term of the lease commenced on January 1, 2016 with expected occupancy in late 2016, after certain leasehold improvements have been completed. The lease payments, which begin on October 1, 2016, will be approximately $15.4 million over the initial 10-year term. We also estimate payments for the Company’s pro rata share of certain real estate taxes, operating expenses and common area maintenance expenses to be approximately $0.9 million for the first year of the lease, and these payments will continue throughout the initial 10-year term. The Company expects to pay approximately $7.3 million for leasehold improvements, net of tenant improvement allowances. Pursuant to the lease, within six months of the expiration of the initial 10-year term, the Company has the option to extend the lease for up to two additional five-year terms, with certain annual increases in base rent.

Additionally, on January 8, 2016 and in conjunction with signing the new lease agreement as discussed above, the Company entered into an amendment to the Company’s current research facility lease for property located at 465 Science Drive Suite C, Madison, Wisconsin with University Research Park, Incorporated that provides for an early termination of such lease effective on October 31, 2016.