Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		15 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021
Lessee Lease Description [Line Items]
Total rent expense	$ 0.3	$ 0.4	$ 0.6	$ 0.8
Lessee, Operating Lease, Existence of Option to Extend [true false]			true
Weighted average remaining operating lease term	2 years 7 months 6 days		2 years 7 months 6 days		2 years 7 months 6 days
Weighted average discount rate of operating lease	6.30%		6.30%		6.30%
Sublease rental income due in future under non-cancelable subleases	$ 1.6		$ 1.6		$ 1.6
Sublease income received					$ 0.0
Operating lease liabilities, cash paid	$ 0.4		$ 0.8
Minimum
Lessee Lease Description [Line Items]
Remaining lease term	1 year		1 year		1 year
Maximum
Lessee Lease Description [Line Items]
Remaining lease term	5 years		5 years		5 years
Operating leases, options to extend leases term	5 years		5 years		5 years