Financial Highlights (Financial Performance Total Returns) (Details) (Trading [Member], USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Class A [Member]
Per share operating performance:
Net asset value of Trading units, beginning of period	$ 76.92	$ 91.32
Trading gain (loss)	$ 0.56	$ (3.16)
Investment income	$ 0.05	$ 0.14
Expenses	$ (1.73)	$ (1.93)
Trading income (loss)	$ (1.12)	$ (4.95)
Net asset value of Trading units, end of period	$ 75.80	$ 86.37
Total return before incentive fees	(1.45%)	(5.42%)
Less incentive fee allocations	0.00%	0.00%
Total return	(1.45%)	(5.42%)
Class B [Member]
Per share operating performance:
Net asset value of Trading units, beginning of period	$ 83.34	$ 96.98
Trading gain (loss)	$ 0.60	$ (3.34)
Investment income	$ 0.06	$ 0.14
Expenses	$ (1.47)	$ (1.60)
Trading income (loss)	$ (0.81)	$ (4.80)
Net asset value of Trading units, end of period	$ 82.53	$ 92.18
Total return before incentive fees	(0.97%)	(4.94%)
Less incentive fee allocations	0.00%	0.00%
Total return	(0.97%)	(4.94%)