Counterparty Risk (% Of Total Collateral On Reverse Repurchase Agreements) (Details)	Sep. 30, 2012
J.P. Morgan Securities Inc. [Member]
Financial Highlights [Line Items]
% of Total Collateral on Reverse Repurchase Agreements	19.00%
Royal Bank Of Canada [Member]
Financial Highlights [Line Items]
% of Total Collateral on Reverse Repurchase Agreements	19.00%
Deutsche Bank [Member]
Financial Highlights [Line Items]
% of Total Collateral on Reverse Repurchase Agreements	16.00%