Schedule Of Investments (Future Contracts) (Parenthetical) (Detail) (USD $)	12 Months Ended																			9 Months Ended
	Dec. 31, 2011 Cocoa (8,925 Contracts, Settlement Date March 15, 2012) [Member] Contract	Dec. 31, 2011 Coffee (2,748 Contracts, Settlement Date March 20, 2012) [Member] Contract	Dec. 31, 2011 Corn (2,176 Contracts, Settlement Date March 14, 2012) [Member] Contract	Dec. 31, 2011 Corn (6,394 Contracts, Settlement Date December 14, 2012) [Member] Contract	Dec. 31, 2011 Cotton (1,229 Contracts, Settlement Date March 08, 2012) [Member] Contract	Dec. 31, 2011 Feeder Cattle (1,217 Contracts, Settlement Date March 29, 2012) [Member] Contract	Dec. 31, 2011 Lean Hogs (4,099 Contracts, Settlement Date February 14, 2012) [Member] Contract	Dec. 31, 2011 Lean Hogs (1,010 Contracts, Settlement Date April 16, 2012) [Member] Contract	Dec. 31, 2011 Live Cattle (5,399 Contracts, Settlement Date February 29, 2012) [Member] Contract	Dec. 31, 2011 Live Cattle (10 Contracts, Settlement Date April 30, 2012) [Member] Contract	Dec. 31, 2011 Red Wheat (1,425 Contracts, Settlement Date July 13, 2012) [Member] Contract	Dec. 31, 2011 Red Wheat (37 Contracts, Settlement Date December 14, 2012) [Member] Contract	Dec. 31, 2011 Soybeans (3,079 Contracts, Settlement Date November 14, 2012) [Member] Contract	Dec. 31, 2011 Soybeans (1,325 Contracts, Settlement Date January 14, 2013) [Member] Contract	Dec. 31, 2011 Sugar (9,767 Contracts, Settlement Date June 29, 2012) [Member] Contract	Dec. 31, 2011 Wheat (1,551 Contracts, Settlement Date July 13, 2012) [Member] Contract	Dec. 31, 2011 Wheat (465 Contracts, Settlement Date December 14, 2012) [Member] Contract	Dec. 31, 2011 Wheat KCB (3,524 Contracts, Settlement Date July 13, 2012) [Member] Contract	Dec. 31, 2011 Net Unrealized Depreciation On Futures Contracts [Member]	Sep. 30, 2012 Cocoa (8,059 Contracts, Settlement Date December 13, 2012) [Member] Contract	Sep. 30, 2012 Coffee (2,395 Contracts, Settlement Date December 18, 2012) [Member] Contract	Sep. 30, 2012 Corn (8,094 Contracts, Settlement Date December 14, 2012) [Member] Contract	Sep. 30, 2012 Cotton (1,143 Contracts, Settlement Date December 6, 2012) [Member] Contract	Sep. 30, 2012 Feeder Cattle (1,031 Contracts, Settlement Date November 15, 2012) [Member] Contract	Sep. 30, 2012 Lean Hogs (4,099 Contracts, Settlement Date December 14, 2012) [Member] Contract	Sep. 30, 2012 Lean Hogs (582 Contracts, Settlement Date February 14, 2013) [Member] Contract	Sep. 30, 2012 Live Cattle (4,501 Contracts, Settlement Date December 31, 2012) [Member] Contract	Sep. 30, 2012 Soybeans (3,460 Contracts, Settlement Date November 14, 2012) [Member] Contract	Sep. 30, 2012 Soybeans (603 Contracts, Settlement Date January 14, 2013) [Member] Contract	Sep. 30, 2012 Sugar (8,414 Contracts, Settlement Date June 28, 2013) [Member] Contract	Sep. 30, 2012 Wheat (265 Contracts, Settlement Date December 14, 2012) [Member] Contract	Sep. 30, 2012 Wheat (2,778 Contracts, Settlement Date July 12, 2013) [Member] Contract	Sep. 30, 2012 Wheat KCB (2,928 Contracts, Settlement Date July 12, 2013 [Member] Contract	Sep. 30, 2012 Net Unrealized Appreciation On Futures Contracts [Member]
Schedule of Investments [Line Items]
Open Option Contracts Written, Number of Contracts	8,925	2,748	2,176	6,394	1,229	1,217	4,099	1,010	5,399	10	1,425	37	3,079	1,325	9,767	1,551	465	3,524		8,059	2,395	8,094	1,143	1,031	4,099	582	4,501	3,460	603	8,414	265	2,778	2,928
Forward Contract Indexed to Issuer's Equity, Settlement Date or Dates	Mar. 15, 2012	Mar. 20, 2012	Mar. 14, 2012	Dec. 14, 2012	Mar. 08, 2012	Mar. 29, 2012	Feb. 14, 2012	Apr. 16, 2012	Feb. 29, 2012	Apr. 30, 2012	Jul. 13, 2012	Dec. 14, 2012	Nov. 14, 2012	Jan. 14, 2013	Jun. 29, 2012	Jul. 13, 2012	Dec. 14, 2012	Jul. 13, 2012		Dec. 13, 2012	Dec. 18, 2012	Dec. 14, 2012	Dec. 06, 2012	Nov. 15, 2012	Dec. 14, 2012	Feb. 14, 2013	Dec. 31, 2012	Nov. 14, 2012	Jan. 14, 2013	Jun. 28, 2013	Dec. 14, 2012	Jul. 12, 2013	Jul. 12, 2013
Securities Unrealized Gain																			$ 148,293,832															$ 195,074,334
Securities Unrealized Loss																			$ 12,872,988															$ 19,604,351