Financial Instruments Owned And Pledged As Collateral At Fair Value, Securities Purchased Under Agreements To Resell And Securities Sold Under Agreements To Repurchase (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	$ 127,178	$ 52,217
Securities Purchased Under Agreements to Resell	2,146	126,401
Securities Sold Under Agreements to Repurchase	(129,577)	(178,683)
Market value of collateral received	2,143	126,386
Market value of collateral pledged	(129,809)	(178,603)
Securities average estimated maturity period, years	3.0
Asset (Liability) Balance [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial Instruments Owned and Pledged as Collateral at Fair Value	127,178	52,217
Securities Purchased Under Agreements to Resell	2,146	126,401
Total Assets	129,324	178,618
Securities Sold Under Agreements to Repurchase	$ (129,577)	$ (178,683)