Counterparty Risk (% Of Total Collateral On Reverse Repurchase Agreements) (Details)	Mar. 31, 2013
Deutsche Bank [Member]
Financial Highlights [Line Items]
% of Total Collateral on Reverse Repurchase Agreements	27.00%
Royal Bank Of Canada [Member]
Financial Highlights [Line Items]
% of Total Collateral on Reverse Repurchase Agreements	22.00%