Financial Highlights - Schedule of Changes in Net Asset Value (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Per Unit Performance (for a unit outstanding throughout the period):
Net asset value per Unit, beginning of period			$ 23.82
Net asset value per Unit, end of period	$ 23.00		23.00
Limited Partners [Member]
Per Unit Performance (for a unit outstanding throughout the period):
Net realized and unrealized gains (losses)	0.95	$ (0.20)	(0.08)	$ (1.16)
Net investment loss	(0.22)	(0.27)	(0.74)	(0.87)
Net increase (decrease) for the period	0.73	(0.47)	(0.82)	(2.03)
Net asset value per Unit, beginning of period	22.27	21.98	23.82	23.54
Net asset value per Unit, end of period	$ 23.00	$ 21.51	$ 23.00	$ 21.51