Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
REVENUE	$ 16,142,321	$ 31,407,709	$ 158,333
Type of Revenue [Extensible List]	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember
OPERATING EXPENSES
Research and development	$ 52,968,505	$ 50,904,466	$ 62,117,818
General and administrative expenses	19,110,051	17,499,152	23,594,888
Impairment expense			2,050,817
Contingent consideration - fair value adjustments			(5,862,464)
TOTAL OPERATING EXPENSES	72,078,556	68,403,618	81,901,059
OPERATING LOSS	(55,936,235)	(36,995,909)	(81,742,726)
OTHER INCOME (EXPENSE)
Interest income (expense), net	1,048,523	415,128	265,794
Change in value of derivatives	432,141	890,362	(301,022)
Other income (expense)	7,493	1,312,524	57,352
TOTAL OTHER INCOME (EXPENSE)	1,488,157	2,618,014	22,124
LOSS BEFORE INCOME TAXES	(54,448,078)	(34,377,895)	(81,720,602)
Provision for income taxes	(2,400)	(2,400)	(2,400)
NET LOSS	$ (54,450,478)	$ (34,380,295)	$ (81,723,002)
NET LOSS PER SHARE - BASIC & DILUTED	$ (0.65)	$ (0.47)	$ (1.34)
Weighted average shares outstanding - basic and diluted	83,638,469	73,898,598	61,050,880
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign Currency Translation Adjustments	$ (54,796)	$ 25,783	$ 143,874
COMPREHENSIVE LOSS	$ (54,505,274)	$ (34,354,512)	$ (81,579,128)