Derivative Instruments (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 instrument	Jun. 30, 2012 instrument	Jun. 30, 2013 instrument	Jun. 30, 2012 instrument
Derivative Instruments
Margin-to-equity ratio (as a percent)			25.00%
Monthly average number of derivative instruments bought and sold	6,401	9,273	6,695	8,363
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	$ (17,513,180)	$ 26,777,604	$ (6,532,821)	$ 32,929,604
Agricultural contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	1,298,274	(1,707,697)	(1,477,013)	(5,347,854)
Currencies contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	(10,146,933)	(98,876)	(4,853,407)	(15,409,354)
Energy contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	(13,322,470)	(8,170,645)	(16,662,161)	8,312,452
Interest rates contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	(9,170,129)	43,835,597	(15,046,385)	27,840,667
Meats contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	1,203,369	(482,758)	1,232,878	(377,806)
Metals contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	13,357,594	2,045,251	12,038,152	(3,670,013)
Soft commodities contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	(1,086,681)	4,261,334	1,253,762	3,462,588
Stock indices contracts
Effect of Derivative Instruments on the Consolidated Statement of Operations
Gains (losses) on derivatives instruments	$ 353,796	$ (12,904,602)	$ 16,981,353	$ 18,118,924