Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Intangible assets and goodwill	$ 1,682	$ 2,271
Inventories and related reserves	12,151	11,298
Deferred revenue and cost of goods sold	4,652	6,816
Other accruals and reserves	2,799	2,336
Accrued compensation	8,317	4,054
Allowance for doubtful accounts	2,346	2,617
Net operating loss and tax credit carryforwards	52,664	43,296
Other, net	2,200	1,748
Total	86,811	74,436
Valuation allowance	(49,014)	(46,271)
Deferred tax asset	37,797	28,165
Withholding taxes		381
Property, plant and equipment	(4,569)	(4,469)
Deferred tax liability	(4,569)	(4,850)
Net deferred tax assets	$ 33,228	$ 23,315