Schedule Of Investments (Future Contracts) (Detail) (USD $)	Dec. 31, 2011 Cocoa (8,925 Contracts, Settlement Date March 15, 2012) [Member]	Dec. 31, 2011 Coffee (2,748 Contracts, Settlement Date March 20, 2012) [Member]	Dec. 31, 2011 Corn (2,176 Contracts, Settlement Date March 14, 2012) [Member]	Dec. 31, 2011 Corn (6,394 Contracts, Settlement Date December 14, 2012) [Member]	Dec. 31, 2011 Cotton (1,229 Contracts, Settlement Date March 08, 2012) [Member]	Dec. 31, 2011 Feeder Cattle (1,217 Contracts, Settlement Date March 29, 2012) [Member]	Dec. 31, 2011 Lean Hogs (4,099 Contracts, Settlement Date February 14, 2012) [Member]	Dec. 31, 2011 Lean Hogs (1,010 Contracts, Settlement Date April 16, 2012) [Member]	Dec. 31, 2011 Live Cattle (5,399 Contracts, Settlement Date February 29, 2012) [Member]	Dec. 31, 2011 Live Cattle (10 Contracts, Settlement Date April 30, 2012) [Member]	Dec. 31, 2011 Red Wheat (1,425 Contracts, Settlement Date July 13, 2012) [Member]	Dec. 31, 2011 Red Wheat (37 Contracts, Settlement Date December 14, 2012) [Member]	Dec. 31, 2011 Soybeans (3,079 Contracts, Settlement Date November 14, 2012) [Member]	Dec. 31, 2011 Soybeans (1,325 Contracts, Settlement Date January 14, 2013) [Member]	Dec. 31, 2011 Sugar (9,767 Contracts, Settlement Date June 29, 2012) [Member]	Dec. 31, 2011 Wheat (1,551 Contracts, Settlement Date July 13, 2012) [Member]	Dec. 31, 2011 Wheat (465 Contracts, Settlement Date December 14, 2012) [Member]	Dec. 31, 2011 Wheat KCB (3,524 Contracts, Settlement Date July 13, 2012) [Member]	Dec. 31, 2011 Net Unrealized Depreciation On Futures Contracts [Member]	Sep. 30, 2012 Cocoa (8,059 Contracts, Settlement Date December 13, 2012) [Member]	Sep. 30, 2012 Coffee (2,395 Contracts, Settlement Date December 18, 2012) [Member]	Sep. 30, 2012 Corn (8,094 Contracts, Settlement Date December 14, 2012) [Member]	Sep. 30, 2012 Cotton (1,143 Contracts, Settlement Date December 6, 2012) [Member]	Sep. 30, 2012 Feeder Cattle (1,031 Contracts, Settlement Date November 15, 2012) [Member]	Sep. 30, 2012 Lean Hogs (4,099 Contracts, Settlement Date December 14, 2012) [Member]	Sep. 30, 2012 Lean Hogs (582 Contracts, Settlement Date February 14, 2013) [Member]	Sep. 30, 2012 Live Cattle (4,501 Contracts, Settlement Date December 31, 2012) [Member]	Sep. 30, 2012 Soybeans (3,460 Contracts, Settlement Date November 14, 2012) [Member]	Sep. 30, 2012 Soybeans (603 Contracts, Settlement Date January 14, 2013) [Member]	Sep. 30, 2012 Sugar (8,414 Contracts, Settlement Date June 28, 2013) [Member]	Sep. 30, 2012 Wheat (265 Contracts, Settlement Date December 14, 2012) [Member]	Sep. 30, 2012 Wheat (2,778 Contracts, Settlement Date July 12, 2013) [Member]	Sep. 30, 2012 Wheat KCB (2,928 Contracts, Settlement Date July 12, 2013 [Member]	Sep. 30, 2012 Net Unrealized Appreciation On Futures Contracts [Member]
Schedule of Investments [Line Items]
Percentage of Net Assets	(2.69%)	(0.30%)	0.18%	(0.40%)	(0.18%)	0.09%	(0.40%)	(0.08%)	(0.34%)	0.00%	(0.04%)	0.00%	0.16%	0.16%	(0.50%)	(0.83%)	(0.03%)	(1.46%)	(6.66%)	0.37%	(0.09%)	3.11%	0.06%	(0.10%)	0.07%	0.03%	(0.44%)	3.37%	0.66%	(0.24%)	0.11%	1.05%	1.20%	9.16%
Fair Value	$ (54,648,710)	$ (6,185,325)	$ 3,723,150	$ (8,096,413)	$ (3,609,715)	$ 1,797,275	$ (8,197,500)	$ (1,585,680)	$ (6,946,470)	$ (11,800)	$ (853,225)	$ 5,613	$ 3,234,838	$ 3,211,075	$ (10,109,557)	$ (16,807,900)	$ (698,525)	$ (29,641,975)	$ (135,420,844)	$ 7,009,240	$ (1,801,800)	$ 59,486,750	$ 1,149,025	$ (1,869,388)	$ 1,360,660	$ 646,880	$ (8,378,040)	$ 64,635,888	$ 12,540,488	$ (4,510,632)	$ 1,980,700	$ 20,185,188	$ 23,035,024	$ 175,469,983