Financial Highlights (Financial Performance Total Expenses) (Details) (Trading [Member])	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Class A [Member]
Ratios to average net assets:
Trading income (loss)	(1.44%)	(3.63%)
Expenses:
Expenses, less incentive fees	(2.28%)	(2.21%)
Less incentive fee allocations	0.00%	0.00%
Total expenses	(2.28%)	(2.21%)
Class B [Member]
Ratios to average net assets:
Trading income (loss)	(1.00%)	(3.69%)
Expenses:
Expenses, less incentive fees	(1.87%)	(1.71%)
Less incentive fee allocations	0.00%	0.00%
Total expenses	(1.87%)	(1.71%)