Consolidated Statements of Operations and Comprehensive Income (Loss) (unaudited) - USD ($)	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
REVENUE	$ 34,657,896	$ 3,509,821
Type of Revenue [Extensible List]	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember	arwr:TechnologyLicensesCollaborativeResearchAndDevelopmentArrangementsResearchGrantsAndProductSalesMember
OPERATING EXPENSES
Research and development	$ 17,572,043	$ 12,919,618
General and administrative expenses	6,139,709	4,403,551
TOTAL OPERATING EXPENSES	23,711,752	17,323,169
OPERATING INCOME (LOSS)	10,946,144	(13,813,348)
OTHER INCOME (EXPENSE)
Interest income (expense), net	1,091,109	163,731
Change in value of derivatives		450,739
TOTAL OTHER INCOME (EXPENSE)	1,091,109	614,470
INCOME (LOSS) BEFORE INCOME TAXES	12,037,253	(13,198,878)
Provision for income taxes	0	0
NET INCOME (LOSS)	$ 12,037,253	$ (13,198,878)
NET INCOME (LOSS) PER SHARE - BASIC	$ 0.13	$ (0.18)
NET INCOME (LOSS) PER SHARE - DILUTED	$ 0.13	$ (0.18)
Weighted average shares outstanding - basic	91,091,823	74,831,415
Weighted average shares outstanding - diluted	95,590,183	74,831,415
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign Currency Translation Adjustments	$ (22,180)	$ (9,528)
COMPREHENSIVE INCOME (LOSS)	$ 12,015,073	$ (13,208,406)