Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
REVENUE	$ 382,000	$ 175,000	$ 290,266
OPERATING EXPENSES
Research and development	47,267,361	23,138,050	8,705,627
Acquired in-process research and development	10,142,786
Salaries and payroll-related costs	16,554,008	12,829,355	6,667,669
General and administrative expenses	7,931,184	5,894,008	3,488,864
Stock-based compensation	10,232,897	5,696,173	1,536,271
Depreciation and amortization	2,336,207	1,345,655	1,751,412
Impairment expense		2,172,387	1,308,047
Contingent consideration - Fair Value Adjustments	1,891,533	2,375,658	1,421,652
TOTAL OPERATING EXPENSES	96,355,976	53,451,286	24,879,542
OPERATING LOSS	(95,973,976)	(53,276,286)	(24,589,276)
OTHER INCOME (EXPENSE)
Equity in income (loss) of unconsolidated affiliates		(78,874)	(641,141)
Gain (loss) on sale of fixed assets, net	19,195	(58,878)	(76,388)
Interest income (expense), net	729,158	645,493	(97,910)
Change in value of derivatives	2,869,267	(6,033,659)	(5,300,389)
Other income (expense)	417,874	82,092	(997,975)
TOTAL OTHER INCOME (EXPENSE)	4,035,494	(5,443,826)	(7,113,803)
LOSS BEFORE INCOME TAXES	(91,938,482)	(58,720,112)	(31,703,079)
Provision for income taxes	(2,400)	(5,300)
LOSS FROM CONTINUING OPERATIONS	(91,940,882)	(58,725,412)	(31,703,079)
Loss from discontinued operations			(354)
NET LOSS FROM DISCONTINUED OPERATIONS			(354)
NET LOSS	(91,940,882)	(58,725,412)	(31,703,433)
Net loss attributable to non-controlling interests		95,222	560,144
NET LOSS ATTRIBUTABLE TO ARROWHEAD	$ (91,940,882)	$ (58,630,190)	$ (31,143,289)
NET LOSS PER SHARE ATTRIBUTABLE TO ARROWHEAD SHAREHOLDERS - BASIC AND DILUTED:	$ (1.60)	$ (1.25)	$ (1.30)
Weighted average shares outstanding - basic and diluted	57,358,442	46,933,030	24,002,224
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX
Foreign Currency Translation Adjustments	$ (136,425)
COMPREHENSIVE LOSS ATTRIBUTABLE TO ARROWHEAD	$ (92,077,307)	$ (58,630,190)	$ (31,143,289)