Receivables From And Payables To Brokers, Dealers And Clearing Organizations (Amounts Receivable From Brokers, Dealers, And Clearing Organizations) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Receivables From And Payables To Brokers, Dealers And Clearing Organizations [Abstract]
Deposits paid for securities borrowed	$ 385,846	$ 227,640
Receivable from clearing organizations	269,235	125,538
Securities failed to deliver	80,197	27,944
Receivables from brokers, dealers and clearing organizations, Total	$ 735,278	$ 381,122