Interest Income And Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest Income Expense Net [Abstract]
Investment securities									$ 53,787	$ 71,526	$ 62,155
Bank loans, net of unearned income									79,816	71,167	38,608
Margin balances									22,421	19,095	18,222
Other									23,077	24,181	23,554
Total interest income									179,101	185,969	142,539
Senior notes									25,695	26,617	20,648
Bank deposits									7,813	7,926	11,775
Other									11,891	6,718	13,945
Total interest expense	$ 12,485	$ 9,796	$ 10,098	$ 13,019	$ 12,560	$ 11,228	$ 8,842	$ 8,631	$ 45,399	$ 41,261	$ 46,368