Statements of Financial Condition (Parenthetical) - shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
General partner: units issued (in shares)	100,000	100,000
General Partner: units outstanding (in shares)	100,000	100,000
Limited partners: units issued (in shares)	96,361,989	96,552,190
Limited partners: units outstanding (in shares)	96,361,989	96,552,190