Collaborative Arrangement - Additional Information (Detail) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue	$ 22,297,000		$ 22,616,000
Abbott Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement payment received	45,800,000
Collaborative arrangement additional potential milestone payments receivable	45,000,000
Total revenue	1,300,000		1,300,000
Collaboration revenue recognized included in balance at beginning of period	1,300,000		$ 1,300,000
Upfront and milestone fee payment included in deferred revenue	14,600,000					$ 15,900,000
Abbott Agreement [Member] | Upfront Payment [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement payment received					$ 25,000,000
Abbott Agreement [Member] | Milestone Payment [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement payment received		$ 10,800,000		$ 10,000,000.0
Abbott Agreement [Member] | Clinical Trial Report Milestone [Member] | TRANSCEND Clinical Trial [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement additional potential milestone payments receivable	15,000,000
Abbott Agreement [Member] | PMA Milestone [Member] | TRANSCEND Clinical Trial [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement additional potential milestone payments receivable	$ 30,000,000