Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Concentration Risk [Line Items]
Total value of shipments made to sell-through distributors but not yet sold through to end customers	$ 3,010,734	$ 1,247,545
Amount of shipments recorded as a reduction to accounts receivable	2,190,703	619,309
Amount of shipments included in deferred revenue	820,031	628,236
Related costs of goods sold deferred and recorded in prepaid expenses and other current assets	2,106,988	910,595
Accrued expense	666,375	488,200
Liabilities for product warranty costs	127,361	45,879
Advertising and promotion expense	$ 6,851,000	$ 6,311,000
Revenues from sales outside the United States, percentage	7.00%	12.00%
Accumulated deficit	$ (191,338,054)	$ (178,478,801)
Accounts Receivable | Two Customers
Concentration Risk [Line Items]
Concentration risk, percentage	66.00%	41.00%
Sales Revenue, Net | Customers
Concentration Risk [Line Items]
Concentration risk, percentage	19.00%	0.00%
Subsequent Event | ASU 2014-09 | Scenario, Forecast
Concentration Risk [Line Items]
Accumulated deficit			$ 300,000