Financial Highlights - Financial Highlights of Limited Partner Class (Detail) - $ / shares		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Per Unit operating performance:
Net asset value at the beginning of the period:		$ 28.83	$ 25.18	$ 30.18	$ 26.48
Net Investment Loss		(0.42)	(0.36)	(1.32)	(1.23)
Realized/Unrealized Gain/(Loss)		0.47	2.23	0.02	1.80
Net income (loss)	[1]	0.05	1.87	(1.30)	0.57
Net asset value at the end of the period:		$ 28.88	$ 27.05	$ 28.88	$ 27.05
Ratios to average net assets:
Net Investment Loss		(5.70%)	(5.60%)	(5.80%)	(6.60%)
Expenses before Incentive Fees		5.70%	5.60%	5.80%	6.60%
Incentive Fees		0.00%	0.00%	0.00%	0.00%
Expenses after Incentive Fees		5.70%	5.60%	5.80%	6.60%
Total return before Incentive Fees		0.20%	7.40%	(4.30%)	2.20%
Incentive Fees		0.00%	0.00%	0.00%	0.00%
Total return after Incentive Fees		0.20%	7.40%	(4.30%)	2.20%

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