Collaborative Arrangement - Additional Information (Detail) - Abbott [Member] - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee received			$ 25,000,000		$ 25,000,000
Collaboration revenue recognized	$ 1,600,000	$ 500,000	4,000,000	$ 500,000
Upfron fee payment included in deferred revenue	16,700,000		16,700,000		$ 20,600,000
Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement additional potential milestone payments receivable	$ 67,000,000		$ 67,000,000