Derivatives (Gains/(Losses) on Derivatives Associated with Interest Rate Risk Management Activities) (Details) - Hedging Instruments And Hedged Items - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Customer Interest Rate Contracts Hedging | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to interest rate derivatives	$ (4,459)	$ 4,099	$ (29,183)	$ 823
Customer Interest Rate Contracts Hedging | Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to interest rate derivatives	4,459	(4,099)	29,183	(823)
Debt Hedging | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to interest rate derivatives	(1,545)	1,808	(8,140)	(992)
Debt Hedging | Term borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to term borrowings	$ 1,520	$ (1,804)	$ 8,070	$ 929