Consolidated Statements of Operations (unaudited) - USD ($)	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
REVENUE	$ 158,333	$ 382,000	$ 175,000
OPERATING EXPENSES
Research and development	41,454,452	47,267,361	23,138,050
Acquired in-process research and development		10,142,786
Salaries and payroll-related costs	19,461,656	16,554,008	12,829,355
General and administrative expenses	9,940,737	7,931,184	5,894,008
Stock-based compensation	11,595,816	10,232,897	5,696,173
Depreciation and amortization	3,260,045	2,336,207	1,345,655
Impairment expense	2,050,817		2,172,387
Contingent consideration - fair value adjustments	(5,862,464)	1,891,533	2,375,658
TOTAL OPERATING EXPENSES	81,901,059	96,355,976	53,451,286
OPERATING LOSS	(81,742,726)	(95,973,976)	(53,276,286)
OTHER INCOME (EXPENSE)
Equity in income (loss) of unconsolidated affiliates			(78,874)
Gain (loss) on sale of fixed assets, net		19,195	(58,878)
Interest income (expense), net	265,794	729,158	645,493
Change in value of derivatives	(301,022)	2,869,267	(6,033,659)
Other income (expense)	57,352	417,874	82,092
TOTAL OTHER INCOME (EXPENSE)	22,124	4,035,494	(5,443,826)
LOSS BEFORE INCOME TAXES	(81,720,602)	(91,938,482)	(58,720,112)
Provision for income taxes	(2,400)	(2,400)	(5,300)
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)
NET LOSS PER SHARE ATTRIBUTABLE TO ARROWHEAD SHAREHOLDERS - BASIC & DILUTED	$ (1.34)	$ (1.60)	$ (1.25)
Weighted average shares outstanding - basic and diluted	61,050,880	57,358,442	46,933,030
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign Currency Translation Adjustments	$ 143,874	$ (136,425)
COMPREHENSIVE LOSS	$ (81,579,128)	$ (92,077,307)	$ (58,630,190)