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Statement of Changes in Partners' Capital (Parenthetical) - shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Statement of Changes in Partners' Capital      
Addition of partnership unit shares 100,000 0 1,300,000
Redemption of partnership unit shares 550,000 1,500,000 3,150,000