Financial Highlights - Schedule of Changes in Net Asset Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class A Redeemable Units [Member]
Per Redeemable Unit Performance (for a unit outstanding throughout the year):
Net realized and unrealized gains (losses)	$ 45.11	$ (25.71)	$ 4.16
Net investment loss	(55.46)	(66.40)	(78.03)
Increase (decrease) for the year	(10.35)	(92.11)	(73.87)
Net asset value per Redeemable Unit, beginning of year	1,162.18	1,254.29	1,328.16
Net asset value per Redeemable Unit, end of year	1,151.83	1,162.18	1,254.29
Class Z Redeemable Units [Member]
Per Redeemable Unit Performance (for a unit outstanding throughout the year):
Net realized and unrealized gains (losses)	37.36	(21.15)
Net investment loss	(26.64)	(2.92)
Increase (decrease) for the year	10.72	(24.07)
Net asset value per Redeemable Unit, beginning of year	953.31	977.38
Net asset value per Redeemable Unit, end of year	$ 964.03	$ 953.31	$ 977.38