Financial Highlights (Financial Performance Total Expenses) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Class A [Member]
Ratios to average net assets:
Trading income (loss)	(0.75%)	(4.94%)	(4.51%)	(8.74%)
Expenses:
Expenses, less incentive fees	(2.13%)	(2.40%)	(4.34%)	(4.56%)
Less incentive fee allocations	(0.02%)	(0.14%)	(0.01%)	(0.26%)
Total expenses	(2.15%)	(2.54%)	(4.35%)	(4.82%)
Class A [Member] | Trading [Member]
Ratios to average net assets:
Trading income (loss)	(1.98%)	4.43%	(6.51%)	(5.39%)
Expenses:
Expenses, less incentive fees	(2.58%)	(2.58%)	(6.86%)	(7.07%)
Less incentive fee allocations	(0.10%)	(0.10%)	(0.07%)	(0.36%)
Total expenses	(2.68%)	(2.68%)	(6.93%)	(7.43%)
Class B [Member]
Ratios to average net assets:
Trading income (loss)	(0.64%)	(4.68%)	(4.48%)	(7.99%)
Expenses:
Expenses, less incentive fees	(1.62%)	(1.93%)	(3.33%)	(3.56%)
Less incentive fee allocations	(0.02%)	(0.13%)	(0.02%)	(0.24%)
Total expenses	(1.64%)	(2.06%)	(3.35%)	(3.80%)
Class B [Member] | Trading [Member]
Ratios to average net assets:
Trading income (loss)	(2.00%)	4.94%	(6.48%)	(3.13%)
Expenses:
Expenses, less incentive fees	(2.06%)	(2.04%)	(5.34%)	(5.59%)
Less incentive fee allocations	(0.10%)	(0.10%)	(0.07%)	(0.34%)
Total expenses	(2.16%)	(2.14%)	(5.41%)	(5.93%)