Recently Adopted Accounting Standard - Summary of Cumulative Effect of Adoption on Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017
Item Effected [Line Items]
Accounts receivable, net	$ 45,052
Inventories, net	43,444		$ 36,499
Total assets	207,665		165,724	$ 166,076
Income taxes payable	708		300
Deferred revenue	4,442		5,791
Sales allowances	567
Total liabilities	31,705		29,305
Retained earnings	122,090		93,605
Total equity	175,960		136,419
Total liabilities and equity	207,665		$ 165,724
Accounting Standards Update 2014-09 [Member]
Item Effected [Line Items]
Sales allowances	567
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Item Effected [Line Items]
Accounts receivable, net	(24)
Inventories, net	(128)
Total assets	(152)
Income taxes payable	(25)
Deferred revenue	4,911
Sales allowances	(497)
Total liabilities	4,389
Retained earnings	(4,541)	$ 3,670
Total equity	(4,541)
Total liabilities and equity	(152)
Accounting Standards Update 2014-09 [Member] | Balances without adoption of Topic 606 [Member]
Item Effected [Line Items]
Accounts receivable, net	45,028
Inventories, net	43,316
Total assets	207,513
Income taxes payable	683
Deferred revenue	9,353
Sales allowances	70
Total liabilities	36,094
Retained earnings	117,549
Total equity	171,419
Total liabilities and equity	$ 207,513