Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (81,723,002)	$ (91,940,882)	$ (58,725,412)
Net loss attributable to non-controlling interests			95,222
NET LOSS ATTRIBUTABLE TO ARROWHEAD	(81,723,002)	(91,940,882)	(58,630,190)
(Gain) loss on disposal of fixed assets		(19,195)	58,878
Change in value of derivatives	301,022	(2,869,267)	6,033,659
Contingent consideration - fair value adjustments	(5,862,464)	1,891,533	2,375,658
Noncash impairment expense	2,050,817		2,172,387
Acquired in-process research and development		10,142,786
Stock-based compensation	11,595,816	10,232,897	5,696,173
Depreciation and amortization	3,260,045	2,336,207	1,345,655
Amortization of note premiums	231,902	1,110,524	793,887
Gain on debt extinguishment			(84,721)
Noncash gain on equity investment			(87,197)
Non-controlling interest			(95,222)
Changes in operating assets and liabilities:
Accounts receivable	(75,000)		75,000
Prepaid expenses and Other Current Assets	(1,020,734)	(3,485,421)	(54,966)
Deferred revenue	5,000,000
Accounts payable	2,554,802	2,497,804	1,412,275
Accrued expenses	(871,833)	4,435,784	3,478,094
Other	131,143	(40,385)	94,257
NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	(64,427,486)	(65,707,615)	(35,416,373)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(3,860,237)	(1,970,612)	(1,717,362)
Proceeds from sale of fixed assets		500	10,000
Purchase of marketable securities			(46,365,528)
Proceeds from sale of marketable securities	17,308,000	26,090,950	11,591,120
Cash paid for acquisitions		(10,000,000)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	13,447,763	14,120,838	(36,481,770)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on capital leases and notes payable	(217,549)	(213,991)	(225,406)
Payments of taxes for net share settled restricted stock unit issuances	(634,187)
Proceeds from the issuance of common stock	52,231,433		172,641,671
Proceeds from the exercise of warrants and stock options	3,752,120	504,512	12,878,044
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	55,131,817	290,521	185,294,309
NET INCREASE (DECREASE) IN CASH	4,152,094	(51,296,256)	113,396,166
CASH AT BEGINNING OF PERIOD	81,214,354	132,510,610	19,114,444
CASH AT END OF PERIOD	85,366,448	81,214,354	132,510,610
Supplementary disclosures:
Interest paid	(11,287)	(14,429)	(25,635)
Property and Equipment purchased through tenant improvement allowance financing	(4,849,360)
Property and Equipment expenditures included in accounts payable and accrued expenses	(4,801,930)
Income Tax Credits Refunded	1,365,288
Income Taxes Paid	$ (2,400)	(2,400)	(5,862)
Galloway Limited
Supplementary disclosures:
Common stock issued to Galloway Limited in settlement of services agreement			$ (500,000)
Novartis
Supplementary disclosures:
Common Stock issued to Novartis for asset acquisition		$ (25,000,000)