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Financial Instruments (Tables)
12 Months Ended
Dec. 31, 2019
Investments, All Other Investments [Abstract]  
Financial Instruments
   2019  2018
   Carrying
Amount
  Fair
Value
  Carrying
Amount
  Fair
Value
Cash  $15,229,000   $15,229,000   $14,036,000   $14,036,000 
Restricted cash   795,000    795,000    363,000    363,000 
Long-term investments   1,150,000    1,150,000    2,358,000    2,358,000 
Accounts receivable   3,190,000    3,190,000    2,615,000    2,615,000