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Schedule II - Valuation and Qualifying Accounts - Summary of Valuation and Qualifying Accounts (Details) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
SEC Schedule, 12-09, Allowance, Credit Loss [Member]    
Balance at beginning of year $ 114,000 $ 137,000
Charged to expenses 4,000 6,000
Deductions (33,000) (29,000)
Balance at end of year 85,000 114,000
SEC Schedule, 12-09, Reserve, Inventory [Member]    
Balance at beginning of year 500,000 794,000
Charged to expenses
Balance at end of year 454,000 500,000
Excess inventory written off (46,000) (294,000)
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member]    
Balance at beginning of year 631,706 45,000
Balance at end of year 2,409,474 631,706
Excess inventory written off $ 1,777,768 $ 586,706