Consolidated Statements of Operations and Comprehensive Income (Loss) (unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
REVENUE	$ 27,375,778	$ 42,696,636	$ 80,359,211	$ 125,502,807
Type of Revenue [Extensible List]	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember
OPERATING EXPENSES
Research and development	$ 32,573,134	$ 19,291,710	$ 85,390,086	$ 57,662,381
General and administrative expenses	10,748,506	4,809,177	38,008,836	16,287,841
TOTAL OPERATING EXPENSES	43,321,640	24,100,887	123,398,922	73,950,222
OPERATING INCOME (LOSS)	(15,945,862)	18,595,749	(43,039,711)	51,552,585
OTHER INCOME (EXPENSE)
Interest income (expense), net	2,334,649	1,739,959	6,919,200	4,717,359
TOTAL OTHER INCOME (EXPENSE)	2,334,649	1,739,959	6,919,200	4,717,359
INCOME (LOSS) BEFORE INCOME TAXES	(13,611,213)	20,335,708	(36,120,511)	56,269,944
NET INCOME (LOSS)	$ (13,611,213)	$ 20,335,708	$ (36,120,511)	$ 56,269,944
NET INCOME (LOSS) PER SHARE - BASIC	$ (0.13)	$ 0.21	$ (0.36)	$ 0.60
NET INCOME (LOSS) PER SHARE - DILUTED	$ (0.13)	$ 0.21	$ (0.36)	$ 0.58
Weighted average shares outstanding - basic	101,843,436	94,935,471	100,184,216	93,364,102
Weighted average shares outstanding - diluted	101,843,436	98,884,744	100,184,216	97,814,019
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign currency translation adjustments	$ 453,895	$ (31,172)	$ 216,405	$ (81,514)
COMPREHENSIVE INCOME (LOSS)	$ (13,157,318)	$ 20,304,536	$ (35,904,106)	$ 56,188,430