Fees (Details) (Maximum [Member])	3 Months Ended
	Mar. 31, 2013
Monthly Payment [Member]
Other Noninterest Expense [Line Items]
Quarterly incentive fee to Advisor as percentage of New Trading Profit	20.00%
Management fee as percentage of month-end net assets	0.167%
Annual Payment [Member]
Other Noninterest Expense [Line Items]
Management fee as percentage of month-end net assets	2.00%