Commitments and Contingencies - Additional Information (Detail)	3 Months Ended		6 Months Ended		36 Months Ended	75 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) ft²	Sep. 30, 2017 USD ($)	Jan. 31, 2018 USD ($) ft²	Sep. 30, 2018 USD ($)
Commitments And Contingencies [Line Items]
Rent expense per month			$ 120,000
Base rent escalators	3.00%		3.00%		3.00%	3.00%
Office space under lease agreement | ft²			45,580
Area of leased office space | ft²					5,803
Lease term					36 months
Lease rental period start date					Feb. 01, 2015
Lease rental period end date					Jan. 31, 2018
Base rent under the lease					$ 12,000
Leasehold improvements						$ 518,000
Rent expense	$ 326,000	$ 365,000	$ 651,000	$ 731,000
Lease Term For Remainder of Total Rentable Square Footage [Member]
Commitments And Contingencies [Line Items]
Lease expiration date			Sep. 01, 2021
Lease option termination description			option to terminate the lease on or after September 1, 2019 with 9 months prior written notice.
Lease For 14,685 of Total Rentable Square Footage [Member]
Commitments And Contingencies [Line Items]
Office space under lease agreement | ft²			14,685
Lease expiration date			Oct. 31, 2018