Counterparty Risk (% Of Total Receivable For Securities Sold) (Details)	Jun. 30, 2013
Royal Bank of Scotland [Member]
Concentration Risk [Line Items]
% of Total Receivable for Securities Sold	36.00%
CS First Boston [Member]
Concentration Risk [Line Items]
% of Total Receivable for Securities Sold	30.00%
Bank Of America [Member]
Concentration Risk [Line Items]
% of Total Receivable for Securities Sold	17.00%