Annual report pursuant to Section 13 and 15(d)

Accrued Expenses (Changes in Accrued Warranty Obligations) (Detail)

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Accrued Expenses (Changes in Accrued Warranty Obligations) (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Class Of Warrant Or Right [Line Items]      
Accrued Warranty Obligations $ 41,132 $ 64,002 $ 39,624
Reductions for Settling Warranties (157,035) (103,265) (67,858)
Warranty Issued During Year 283,406 80,395 92,236
Accrued Warranty Obligations $ 167,503 $ 41,132 $ 64,002