v2.4.0.8
Segment And Geographic Information (Segment Table) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Dec. 31, 2013
Segment Reporting Information [Line Items]          
Net revenues $ 309,299 $ 283,956 $ 664,207 $ 500,030  
Income before income taxes 174,209 133,926 392,353 216,149  
Assets 40,155,499   40,155,499   37,870,700
Electronic Brokerage [Member]
         
Segment Reporting Information [Line Items]          
Net revenues 220,600 212,500 444,300 407,800  
Income before income taxes 131,400 123,300 265,700 234,300  
Assets 34,560,600   34,560,600   31,333,500
Market Making [Member]
         
Segment Reporting Information [Line Items]          
Net revenues 91,900 67,400 225,000 91,000  
Income before income taxes 46,500 7,600 134,600 (21,400)  
Assets 12,190,700   12,190,700   12,139,500
Corporate And Eliminations [Member]
         
Segment Reporting Information [Line Items]          
Net revenues (3,200) 4,000 (5,100) 1,200  
Income before income taxes (3,700) 3,000 (8,000) 3,200  
Assets $ (6,595,800)   $ (6,595,800)   $ (5,602,300)