Financial Highlights - Financial Highlights for the Limited Partner Class (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Per Unit Performance (for a unit outstanding throughout the period):
Net asset value per Unit, beginning of period	$ 23.36
Net asset value per Unit, end of period	22.92
Limited Partners [Member]
Per Unit Performance (for a unit outstanding throughout the period):
Net realized and unrealized gains (losses)	(0.19)	$ 0.57
Net investment loss	(0.25)	(0.18)
Net increase (decrease) for the period	(0.44)	0.39
Net asset value per Unit, beginning of period	23.36	20.45
Net asset value per Unit, end of period	$ 22.92	$ 20.84
Ratios to Average Limited Partners' Capital:
Net investment loss	(4.40%)	(3.60%)
Operating expenses before incentive fees	5.20%	5.30%
Incentive fees	0.00%	0.00%
Operating expenses after incentive fees	5.20%	5.30%
Total return:
Total return before incentive fees	(1.90%)	1.90%
Incentive fees	0.00%	0.00%
Total return after incentive fees	(1.90%)	1.90%