Counterparty Risk (% Of Total Collateral On Reverse Repurchase Agreements) (Details)	Jun. 30, 2012
Credit Suisse Group [Member]
% of Total Collateral on Reverse Repurchase Agreements	20.00%
J.P. Morgan Securities Inc. [Member]
% of Total Collateral on Reverse Repurchase Agreements	20.00%
Deutsche Bank [Member]
% of Total Collateral on Reverse Repurchase Agreements	16.00%