Financial Instruments Owned And Pledged As Collateral At Fair Value, Securities Purchased Under Agreements To Resell And Securities Sold Under Agreements To Repurchase (Summary Of Transactions Related Assets, Liabilities And Collateral Received Or Pledged) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule Of Financial Instruments Owned And Pledged As Collateral Securities Purchased Under Agreements To Resell And Securities Sold Under Agreements To Repurchase [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	$ 139,209	$ 127,178
Securities Purchased Under Agreements to Resell	973	2,146
Securities Sold Under Agreements to Repurchase	(140,443)	(129,577)
Market Value Of Collateral Received Or (Pledged) [Member]
Schedule Of Financial Instruments Owned And Pledged As Collateral Securities Purchased Under Agreements To Resell And Securities Sold Under Agreements To Repurchase [Line Items]
Securities Purchased Under Agreements to Resell	975	2,143
Securities Sold Under Agreements to Repurchase	(140,650)	(129,809)
Asset (Liability) Balance [Member]
Schedule Of Financial Instruments Owned And Pledged As Collateral Securities Purchased Under Agreements To Resell And Securities Sold Under Agreements To Repurchase [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	139,209	127,178
Securities Purchased Under Agreements to Resell	973	2,146
Total Assets	140,182	129,324
Securities Sold Under Agreements to Repurchase	$ (140,443)	$ (129,577)