Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
REVENUE	$ 727,375	$ 9,342,498	$ 4,887,321	$ 22,693,923
Type of Revenue [Extensible List]	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember
OPERATING EXPENSES
Research and development	$ 12,052,653	$ 11,136,741	$ 36,974,625	$ 37,363,207
General and administrative expenses	4,594,441	3,919,921	12,679,822	12,076,412
TOTAL OPERATING EXPENSES	16,647,094	15,056,662	49,654,447	49,439,619
OPERATING LOSS	(15,919,719)	(5,714,164)	(44,767,126)	(26,745,696)
OTHER INCOME (EXPENSE)
Interest income (expense), net	313,702	131,358	645,778	265,250
Change in value of derivatives		63,065	432,141	1,519,513
Other income (expense)				1,312,524
TOTAL OTHER INCOME (EXPENSE)	313,702	194,423	1,077,919	3,097,287
LOSS BEFORE INCOME TAXES	(15,606,017)	(5,519,741)	(43,689,207)	(23,648,409)
NET LOSS	$ (15,606,017)	$ (5,519,741)	$ (43,689,207)	$ (23,648,409)
NET LOSS PER SHARE - BASIC & DILUTED	$ (0.18)	$ (0.07)	$ (0.53)	$ (0.32)
Weighted average shares outstanding - basic and diluted	87,634,435	74,772,103	82,149,381	73,603,852
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign Currency Translation Adjustments	$ (28,603)	$ 12,309	$ (36,570)	$ (25,835)
COMPREHENSIVE LOSS	$ (15,634,620)	$ (5,507,432)	$ (43,725,777)	$ (23,674,244)