Post-effective amendment to a registration statement that is not immediately effective upon filing

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounts receivable (Details)

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounts receivable (Details) - USD ($)
12 Months Ended
Jun. 09, 2014
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Allowance rollforward        
Balance at beginning of year   $ 1,545,000 $ 1,528,000  
Provision   211,696 54,939 $ 618,786
Write-offs   (105,000) (38,000)  
Balance at end of year   1,652,000 1,545,000 $ 1,528,000
Unbilled receivables, current   $ 615,000 $ 1,860,000  
Estimated residual value $ 1,085,000      
Asset impairment 2,500,000      
Insurance receivable $ 2,500,000