Derivative Financial Instruments (Unrealized And Realized Gains (Losses) On Derivative Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	$ (201,124)	$ 62,535	$ (595,085)	$ 41,132
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	(27,354)	25,308	(101,744)	580
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	11,089	6,893	15,992	30,417
Equity Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	(184,020)	68,649	(505,872)	28,008
Commodity Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	2,777	(33,940)	351	(17,261)
Credit Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	$ (3,616)	$ (4,375)	$ (3,812)	$ (612)