Financial Highlights (Financial Performance Total Returns) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012	Mar. 31, 2011
Class A [Member]
Per share operating performance:
Total return before incentive fees	(2.81%)	(4.75%)	(8.09%)	(8.19%)
Less incentive fee allocations	(0.02%)	(0.14%)	(0.01%)	(0.26%)
Total return	(2.83%)	(4.89%)	(8.10%)	(8.45%)
Class B [Member]
Per share operating performance:
Total return before incentive fees	(2.32%)	(4.28%)	(7.14%)	(7.29%)
Less incentive fee allocations	(0.02%)	(0.13%)	(0.02%)	(0.24%)
Total return	(2.34%)	(4.41%)	(7.16%)	(7.53%)
Trading [Member] | Class A [Member]
Per share operating performance:
Net asset value of Trading units, beginning of period	$ 91.32	$ 100.64	$ 91.32	$ 100.64	$ 86.37	$ 96.88
Trading gain (loss)	$ (1.73)	$ 6.39	$ (5.59)	$ 1.45
Investment income	$ 0.1	$ 0.29	$ 0.32	$ 0.51
Expenses	$ (2.04)	$ (2.53)	$ (5.79)	$ (6.31)
Trading income (loss)	$ (3.67)	$ 4.15	$ (11.06)	$ (4.35)
Net asset value of Trading units, end of period	$ 83.93	$ 92.14	$ 83.93	$ 92.14	$ 86.37	$ 96.88
Total return before incentive fees	(4.48%)	4.61%	(12.18%)	(3.96%)
Less incentive fee allocations	(0.10%)	(0.10%)	(0.07%)	(0.36%)
Total return	(4.58%)	4.51%	(12.25%)	(4.32%)
Trading [Member] | Class B [Member]
Per share operating performance:
Net asset value of Trading units, beginning of period	$ 96.98	$ 104.75	$ 96.98	$ 104.75	$ 92.18	$ 101.34
Trading gain (loss)	$ (1.87)	$ 6.73	$ (5.98)	$ 2.28
Investment income	$ 0.11	$ 0.3	$ 0.34	$ 0.56
Expenses	$ (1.75)	$ (2.16)	$ (4.82)	$ (5.85)
Trading income (loss)	$ (3.51)	$ 4.87	$ (10.46)	$ (3.01)
Net asset value of Trading units, end of period	$ 90.03	$ 96.87	$ 90.03	$ 96.87	$ 92.18	$ 101.34
Total return before incentive fees	(4.00%)	5.13%	(10.85%)	(2.54%)
Less incentive fee allocations	(0.10%)	(0.10%)	(0.07%)	(0.34%)
Total return	(4.10%)	5.03%	(10.92%)	(2.88%)