Interest Income And Interest Expense (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Interest Income Expense Net [Abstract]
Bank loans, net		$ 35,484	$ 20,705	$ 91,517	$ 60,460
Investment securities		27,161	10,641	73,968	38,674
Margin balances		7,438	6,183	24,135	15,668
Other		4,798	5,847	13,868	15,162
Total interest income		74,881	43,376	203,488	129,964
Senior notes	[1]	12,164	5,408	28,518	19,364
Bank deposits		3,628	1,783	10,763	5,945
Other		3,591	2,605	11,475	7,605
Total interest expense		$ 19,383	$ 9,796	$ 50,756	$ 32,914

[1] Includes $3.0 million related to the write-off of debt issuance costs as a result of the redemption of the Company’s $150.0 million 5.375% senior notes in July 2016.