Business and Basis of Presentation (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Organization And Basis Of Presentation [Line Items]
Accumulated deficit	$ 181,711,201		$ 178,478,801
Cash and cash equivalents	6,897,161	$ 8,739,651	3,949,135	$ 12,462,872
Value of shipments made but not yet sold	1,571,465		1,247,545
Reduction to accounts receivable	826,261		619,309
Deferred revenue	745,204		628,236
Deferred costs of goods sold	966,781		910,595
Provision for expected returns recorded as accrued expense	323,403		488,200
Allowance for doubtful accounts	$ 25,000		$ 25,000
Minimum
Organization And Basis Of Presentation [Line Items]
Product sales right of return term	30 days
Maximum
Organization And Basis Of Presentation [Line Items]
Product sales right of return term	60 days
2017 Offering
Organization And Basis Of Presentation [Line Items]
Gross proceeds from issuance of equity	$ 7,000,000
Net proceeds from issuance of stock and warrants	$ 6,300,000
Customer Concentration Risk | One Customer | Revenue
Organization And Basis Of Presentation [Line Items]
Concentration risk, percentage	17.00%
Customer Concentration Risk | Two Customers | Revenue
Organization And Basis Of Presentation [Line Items]
Concentration risk, percentage		25.00%
Customer Concentration Risk | Two Customers | Accounts Receivable
Organization And Basis Of Presentation [Line Items]
Concentration risk, percentage			41.00%
Customer Concentration Risk | Three Customers | Accounts Receivable
Organization And Basis Of Presentation [Line Items]
Concentration risk, percentage	53.00%