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Statements of Changes in Partners' Capital [Parenthetical] - shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Addition of partnership units 6,800,000 2,250,000 2,800,000
Redemption of partnership units 1,900,000 1,000,000 3,300,000