Interest Income And Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest Income And Interest Expense [Abstract]
Investment securities	$ 17,514	$ 11,718	$ 44,046	$ 33,657
Bank loans, net of unearned income	8,819	7,329	26,489	20,755
Margin balances	4,722	4,781	13,521	14,587
Other	8,075	2,532	17,773	9,729
Total interest income	39,130	26,360	101,829	78,728
Senior notes	5,164	3,048	15,484	8,388
Bank deposits	2,636	3,606	8,365	11,951
Other	3,735	(750)	10,889	4,429
Total interest expense	$ 11,535	$ 5,904	$ 34,738	$ 24,768