Accrued Expenses (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Sales return allowance	$ 666,375	$ 488,200
Professional services	603,000	390,800
Technology fees	450,000	450,000
Advertising	160,800	28,100
Warranty	127,361	45,879
Other	234,779	245,752
Accrued expenses	$ 2,242,315	$ 1,648,731