Income Taxes - Components of Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets:
Net operating loss carryforward	$ 2,341	$ 2,347
Deferred revenue	15,348	13,304
Deferred compensation	971	858
Lease liability	2,460
Inventory reserve	1,258	1,294
Stock-based compensation	10,769	3,758
Amortization	1,133	412
Research and development tax credit carryforward	4,957	5,193
Reserves, accruals, and other	3,394	3,094
Total deferred income tax assets	42,631	30,260
Deferred income tax liabilities:
Customer contract asset	(883)	0
Right of use asset	(2,228)	0
Depreciation	(3,715)	(2,195)
Amortization	(62)	(57)
Other	(1,237)	(1,232)
Total deferred income tax liabilities	(8,125)	(3,484)
Net deferred income tax assets before valuation allowance	34,506	26,776
Valuation allowance	(7,172)	(7,429)
Net deferred income tax assets	$ 27,334	$ 19,347