Financial Instruments (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Investment Holdings [Line Items]
Net unrealized gains (losses) on open contracts	$ (4,017,777)	$ 89,949
Cash held by acting commodity futures brokers administrating open contracts	53,858,883	60,196,245
Exchange-Traded [Member]
Investment Holdings [Line Items]
Net unrealized gains (losses) on open contracts	(3,092,436)	(1,240,461)
Longest maturities	2014-09	2013-09
Off-Exchange-Traded [Member]
Investment Holdings [Line Items]
Net unrealized gains (losses) on open contracts	$ (925,341)	$ 1,330,410
Longest maturities	2012-09	2012-03