Collaborative Arrangement - Additional Information (Detail) - Abbott [Member] - USD ($)	3 Months Ended	12 Months Ended
	Dec. 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	2,400,000
Upfron fee payment included in deferred revenue	18,300,000
Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement additional potential milestone payments receivable	$ 67,000,000