Financial Highlights - Ratios to Average Limited Partners' Capital (Detail) - Limited Partners [Member]	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Ratios to Average Limited Partners' Capital:
Net investment loss	(5.40%)	(5.50%)
Operating expenses before incentive fees	5.90%	5.70%
Incentive fees	0.00%	0.00%
Operating expenses after incentive fees	5.90%	5.70%
Total return before incentive fees	(2.50%)	(2.60%)
Incentive fees	(0.00%)	(0.00%)
Total return after incentive fees	(2.50%)	(2.60%)