Consolidated Statements of Operations and Comprehensive Income (Loss) (unaudited) - USD ($)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
REVENUE	$ 29,454,579	$ 34,657,896
Type of Revenue [Extensible List]	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember
OPERATING EXPENSES
Research and development	$ 23,373,616	$ 17,572,043
General and administrative expenses	10,934,557	6,139,709
TOTAL OPERATING EXPENSES	34,308,173	23,711,752
OPERATING INCOME (LOSS)	(4,853,594)	10,946,144
OTHER INCOME (EXPENSE)
Interest income (expense), net	2,179,866	1,091,109
TOTAL OTHER INCOME (EXPENSE)	2,179,866	1,091,109
INCOME (LOSS) BEFORE INCOME TAXES	(2,673,728)	12,037,253
NET INCOME (LOSS)	$ (2,673,728)	$ 12,037,253
NET INCOME (LOSS) PER SHARE - BASIC	$ (0.03)	$ 0.13
NET INCOME (LOSS) PER SHARE - DILUTED	$ (0.03)	$ 0.13
Weighted average shares outstanding - basic	97,090,079	91,091,823
Weighted average shares outstanding - diluted	97,090,079	95,590,183
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign currency translation adjustments	$ 196,074	$ (22,180)
COMPREHENSIVE INCOME (LOSS)	$ (2,477,654)	$ 12,015,073