Financial Highlights (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Per Unit operating performance: [Abstract]
Net asset value at the beginning of the period (in dollars per unit)	$ 9.33		$ 10.22		$ 10.54		$ 9.69
Interest Income (in dollars per unit)	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]
Expenses (in dollars per unit)	$ (0.14)		$ (0.22)		$ (0.36)		$ (0.42)
Realized/Unrealized Income (in dollars per unit )	$ 0.54	[2]	$ 0.65	[2]	$ (0.45)	[2]	$ 1.38	[2]
Net Income (Loss) (in dollars per unit)	$ 0.40	[3]	$ 0.43	[3]	$ (0.81)	[3]	$ 0.96	[3]
Net asset value at the end of the period (in dollars per unit)	$ 9.73		$ 10.65		$ 9.73		$ 10.65
Ratios to average net assets: [Abstract]
Net Investment Loss (in hundredths)	(6.10%)	[4]	(8.10%)	[4]	(7.60%)	[4]	(8.10%)	[4]
Expenses before Incentive Fees (in hundredths)	6.10%	[4]	8.10%	[4]	7.60%	[4]	8.10%	[4]
Expenses after Incentive Fees (in hundredths)	6.10%	[4]	8.10%	[4]	7.60%	[4]	8.10%	[4]
Total return before incentive fees (in hundredths)	4.30%		4.20%		(7.70%)		9.90%
Total return after incentive fees (in hundredths)	4.30%		4.20%		(7.70%)		9.90%

[1] Amounts less than $0.005 per Unit.

[2] Realized/Unrealized Income is a balancing amount necessary to reconcile the change in net asset value per Unit with the other per Unit information.

[3] Based on change in net asset value per Unit.

[4] Annualized (except for incentive fees if applicable).