Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Lessee Lease Description [Line Items]
Total rent expense	$ 0.4	$ 0.4	$ 1.1	$ 1.0
Lessee, Operating Lease, Existence of Option to Extend [true false]			true
Weighted average remaining operating lease term	3 years 4 months 24 days		3 years 4 months 24 days
Weighted average discount rate of operating lease	6.40%		6.40%
Sublease rental income due in future under non-cancelable subleases	$ 2.1		$ 2.1
Operating lease liabilities, cash paid	0.5		1.6
Sublease rental income	$ 0.2		$ 0.6
Minimum
Lessee Lease Description [Line Items]
Remaining lease term			1 year
Maximum
Lessee Lease Description [Line Items]
Remaining lease term			7 years
Operating leases, options to extend leases term	5 years		5 years