Derivative Financial Instruments (Unrealized And Realized Gains (Losses) On Derivative Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in Interest expense on fair value hedge	$ 60	$ 1,537	$ 1,692	$ 4,390
Unrealized and realized gains (losses)	3,364	(159,304)	(229,146)	(285,866)
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	13,951	(7,485)	36,053	2,555
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	(4,781)	481	6,737	3,341
Equity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	1,019	(142,931)	(249,546)	(294,635)
Commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	(6,845)	(1,422)	(23,150)	(3,260)
Credit contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized and realized gains (losses)	20	(7,947)	760	6,133
Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in Interest expense on fair value hedge	(1,161)	6,217	(22,363)	13,960
Long-term Debt
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in Interest expense on fair value hedge	$ 1,221	$ (4,680)	$ 24,055	$ (9,570)