Collaboration and License Agreements - Amgen, Inc. (Details)	1 Months Ended	3 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($) agreement	Jun. 30, 2024 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jul. 31, 2020 USD ($)	Sep. 30, 2018 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from the issuance of common stock, net of offering costs				$ 429,265,000	$ 0	$ 0
Contract liabilities				0	866,000
Upfront payment received				0	250,000,000
Milestone payment received				50,000,000	$ 0
Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received			$ 250,000,000.0
Milestone payment received		$ 50,000,000
Amgen | Olpasiran Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of agreements | agreement	2
Upfront payment	$ 35,000,000.0
Proceeds from the issuance of common stock, net of offering costs	$ 21,500,000
Milestone payments			$ 25,000,000.0	55,000,000.0			$ 20,000,000.0	$ 10,000,000.0
Contract assets				0
Contract liabilities				0
Amgen | Olpasiran Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional remaining development regulatory and sales milestones payments				$ 485,000,000.0