Financial Highlights - Financial Highlights for Limited Partner Class (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Per Unit Performance (for unit outstanding throughout the period):
Net realized and unrealized gains (losses)	$ 0.12	$ 1.30
Net investment loss	(0.17)	(0.18)
Increase (decrease) for the period	(0.05)	1.12
Net asset value per Unit, beginning of period	12.08	12.72
Net asset value per Unit, end of period	$ 12.03	$ 13.84
Ratios to Average Limited Partners' Capital:
Net investment loss	(5.40%)	(5.50%)
Operating expenses before incentive fees	5.60%	5.50%
Incentive fees	0.00%	0.00%
Operating expenses after incentive fees	5.60%	5.50%
Total return:
Total return before incentive fees	(0.40%)	8.80%
Incentive fees	0.00%	0.00%
Total return after incentive fees	(0.40%)	8.80%