Financial Highlights - Financial Highlights for the Limited Partner Class (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 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	$ 22.80		22.80
Limited Partners [Member]
Per Unit Performance (for a unit outstanding throughout the period):
Net realized and unrealized gains (losses)	0.17	$ 1.30	(0.02)	$ 1.87
Net investment loss	(0.29)	(0.19)	(0.54)	(0.37)
Net increase (decrease) for the period	(0.12)	1.11	(0.56)	1.50
Net asset value per Unit, beginning of period	22.92	20.84	23.36	20.45
Net asset value per Unit, end of period	$ 22.80	$ 21.95	$ 22.80	$ 21.95
Ratios to Average Limited Partners' Capital:
Net investment loss	(5.10%)	(3.60%)	(4.80%)	(3.60%)
Operating expenses	5.50%	5.80%	5.60%	5.70%
Expenses reimbursed by the General Partner	(0.30%)	(0.60%)	(0.30%)	(0.40%)
Incentive fees	0.00%	0.00%	0.00%	0.00%
Total expenses	5.20%	5.20%	5.30%	5.30%
Total return:
Total return before incentive fees	(0.50%)	5.30%	(2.40%)	7.30%
Incentive fees	0.00%	0.00%	0.00%	0.00%
Total return after incentive fees	(0.50%)	5.30%	(2.40%)	7.30%