Interest Income And Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Interest Income Expense Net [Abstract]
Bank loans, net	$ 29,475	$ 20,952	$ 56,033	$ 39,937
Investment securities	24,446	13,618	46,807	28,372
Margin balances	8,151	5,123	16,697	9,485
Other	3,708	4,159	9,070	8,794
Total interest income	65,780	43,852	128,607	86,588
Senior notes	8,179	5,333	16,354	13,984
Bank deposits	4,477	2,047	7,135	4,162
Other	4,606	2,718	7,884	4,971
Total interest expense	$ 17,262	$ 10,098	$ 31,373	$ 23,117