Schedule of Valuation and Qualifying Accounts (Tables)
 12 Months Ended
Dec. 31, 2013
Valuation and Qualifying Accounts [Abstract]  
Allowance for Credit Losses on Financing Receivables [Table Text Block]

Description

 

Balance at

Beginning

of Period

   

Charged to

Costs and

Expenses

     

Deductions

     

Balance at

End of

Period

 
                                     

December 31, 2011:

                                   

Allowance for doubtful accounts (A)

  $ 371,340     $ 81,000  

(B)

  $ 159,279  

(C)

  $ 293,061  
                                     

December 31, 2012:

                                   

Allowance for doubtful accounts (A)

  $ 293,061     $ 48,000       $ —       $ 341,061  
                                     

December 31, 2013:

                                   

Allowance for doubtful accounts (A)

  $ 341,061     $ 103,322  

(D)

  $ 57,602       $ 386,781