Financial Highlights - Financial Highlights for Limited Partner Class (Detail) - $ / shares		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Per Unit operating performance:
Net asset value at the beginning of period (in dollars per unit)		$ 13.84	$ 9.33	$ 12.72	$ 10.54
Net Investment Loss (in dollars per unit)		(0.19)	(0.14)	(0.37)	(0.36)
Realized/Unrealized Gain (Loss) (in dollars per unit)		(1.85)	0.54	(0.55)	(0.45)
Net Income (Loss) (in dollars per unit)	[1]	(2.04)	0.40	(0.92)	(0.81)
Net asset value at the ending of the period (in dollars per unit)		$ 11.80	$ 9.73	$ 11.80	$ 9.73
Ratios to average net assets:
Net Investment Loss (in hundredths)		(5.70%)	(6.10%)	(5.70%)	(7.60%)
Expenses before Incentive Fees (in hundredths)		5.70%	6.10%	5.70%	7.60%
Incentive Fees (in hundredths)		0.00%	0.00%	0.00%	0.00%
Expenses after Incentive Fees (in hundredths)		5.70%	6.10%	5.70%	7.60%
Total return before Incentive Fees (in hundredths)		(14.70%)	4.30%	(7.20%)	(7.70%)
Incentive Fees (in hundredths)		0.00%	0.00%	0.00%	0.00%
Total return after Incentive Fees (in hundredths)		(14.70%)	4.30%	(7.20%)	(7.70%)

[1] Represents the change in net asset value per Unit during the period.