Leases - Additional Information (Detail) ft² in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2017 USD ($) ft²	Jan. 31, 2012 USD ($) ft² Option $ / ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Leases [Abstract]
Lease agreement area (square feet) | ft²	44	66
Lease term		120 months
Number of options to extend the term | Option		2
Extend option term		5 years
Initial annual rent payments per square foot | $ / ft²		27.00
Rent payments due in initial five months	$ 0	$ 0		$ 0
Percentage of annual rent increase		3.00%
Allowance for tenant improvements		$ 3,300,000
Sublease loss	1,600,000		$ 0	1,584,000
Deferred liability			1,600,000
Lessor, Lease, Description [Line Items]
Other current liabilities	1,424,000		893,000	1,424,000
Other liabilities	5,469,000		4,571,000	5,469,000
Sublease-related income			1,600,000	100,000
Rent expense, net of sublease income			100,000	1,600,000
Sublease
Lessor, Lease, Description [Line Items]
Other current liabilities	800,000		200,000	800,000
Other liabilities	$ 600,000		$ 400,000	$ 600,000