Earnings Per Share (Tables)

12 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table presents the computation of basic and diluted earnings per share for the years ended September 30, 2023, 2022 and 2021.

	Year Ended September 30,
	2023		2022		2021
	(in thousands, except per share amounts)
Numerator:
Net loss attributable to Arrowhead Pharmaceuticals, Inc.	$	(205,275)	$	(176,063)	$	(140,848)
Denominator:
Weighted-average basic shares outstanding	106,750		105,426		103,745
Effect of dilutive securities	—		—		—
Weighted-average diluted shares outstanding	106,750		105,426		103,745
Basic earnings per share	$	(1.92)	$	(1.67)	$	(1.36)
Diluted earnings per share	$	(1.92)	$	(1.67)	$	(1.36)