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FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS (Details Textual) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Percentage Of Management Fee In Average Daily Total Net Assets 0.75%    
Estimated Investor Tax Reporting Cost $ 111,000 $ 190,000 $ 174,000
Percentage Of Fees and Other Waivers Expense 0.15%    
Expenses Write Off $ 81,642    
BNO [Member]      
Estimated Directors Fees and Expenses 521,689 536,375 582,050
BNO and Related Public Fund [Member]      
Estimated Directors Fees and Expenses $ 15,970 $ 13,325 $ 11,565