Collaborative Arrangement - Additional Information (Detail) - Abbott [Member]	12 Months Ended
	Sep. 30, 2018 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee received	$ 25,000,000
Collaboration revenue recognized	4,400,000
Deferred revenue, current	9,600,000
Long-term deferred revenue	11,100,000
Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement additional potential milestone payments receivable	$ 67,000,000