Leases - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Jul. 31, 2017 USD ($) ft²	Jul. 31, 2015 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($) Agreement	Oct. 31, 2016 USD ($)
Lessee Lease Description [Line Items]
Operating Lease Annual Rent			$ 2,500,000
Rent credit due to accelerated amortization of deferred rent				$ 200,000
Remaining amortization period of deferred rent and remaining useful life leasehold improvements	63 months
Revised amortization period of deferred rent and revised useful life leasehold improvements	7 months	7 months
Laboratory and office space to be leased | ft²	41,346
Operating lease annual rent	$ 3,100,000	$ 900,000
Term of lease	10 years	63 months
Tenant improvement investment	$ 1,600,000
Capitalized landlord tenant improvement funded			$ 5,000,000
Letter of credit	1,000,000
Lease commencement date		2016-02
Lease expiration date		2021-04	2017-07
Renewal term of lease		1 year
Agreement termination term		30 days
Penalty on contract termination		$ 0
Yearly increases in base rent		3.00%
Rent abatement term		3 months
Number of non cancellable lease agreements | Agreement					2
Non cancellable lease agreements description			the present value of the lease exceeds 90% of the fair market value.
Agreement termination			2018-11
Non-cancellable Lease Agreement Three
Lessee Lease Description [Line Items]
Term of non-cancellable lease					36 months
Non-cancellable lease					$ 200,000
Interest rate on outstanding capital lease obligation			1.10%
Non-cancellable Lease Agreement Four
Lessee Lease Description [Line Items]
Term of non-cancellable lease					36 months
Non-cancellable lease					$ 700,000
Interest rate on outstanding capital lease obligation			7.30%
Non Cancellable Lease Agreement Two
Lessee Lease Description [Line Items]
Term of non-cancellable lease						24 months
Non-cancellable lease						$ 400,000
Interest rate on outstanding capital lease obligation				9.60%
Maximum
Lessee Lease Description [Line Items]
Tenant improvement investment	$ 6,600,000