Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2017
California [Member]
Loss Contingencies [Line Items]
Lease expiration date	Jun. 30, 2021
Term of lessee's operating lease renewal	5 years
North Carolina [Member]
Loss Contingencies [Line Items]
Lease expiration date	Nov. 30, 2014
Term of lessee's operating lease renewal	3 months
Massachusetts [Member]
Loss Contingencies [Line Items]
Lease expiration date	Nov. 30, 2015
Term of lessee's operating lease renewal	1 year