Commitments and Contingencies - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Loss Contingencies [Line Items]
Operating lease expiration year	2023
Rent expense	$ 4,900,000	$ 4,600,000
Tenant improvement allowances	0	0
Restricted cash	2,300,000		$ 2,000,000
Purchase commitments	$ 3,500,000		3,800,000
Period of purchase commitment of inventory from specified date	6 months
Loss contingency accrual	$ 0		$ 0
Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Motor vehicle lease expenses	3,400,000	$ 2,100,000
Maximum [Member] | Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Penalties	$ 100,000