Collaboration and License Agreements - Horizon Therapeutics Ireland DAC - Additional Information (Detail) $ in Thousands		3 Months Ended		9 Months Ended
	Jun. 18, 2021 USD ($) obligation bundle	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jul. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 32,412	$ 45,891	$ 211,656	$ 100,004
Contract liabilities		84,288		84,288		$ 111,055
Horizon Therapeutics Ireland DAC | ARO-XDH
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement							$ 40,000
Number of distinct performance obligations | obligation	1
Initial transaction price	$ 40,000
Revenues		6,700	$ 0	20,000	0
Contract assets		0		0
Contract liabilities		13,300		13,300
Horizon Therapeutics Ireland DAC | License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle | bundle	1
Number of distinct performance obligations | obligation	1
Horizon Therapeutics Ireland DAC | ARO-XDH Supply Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues				1,300	$ 0
Contract assets		0		0
Contract liabilities		$ 0		$ 0
Horizon Therapeutics Ireland DAC | Maximum | ARO-XDH
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments							$ 660,000