Derivatives (Gains/(Losses) on Derivatives Associated with Interest Rate Risk Management Activities) (Details) - Hedging Instruments And Hedged Items - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Customer Interest Rate Contracts Hedging | Customer Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) Related to Interest Rate Derivatives	$ (180)	$ (1,964)	$ 643	$ 18,749
Customer Interest Rate Contracts Hedging | Offsetting Upstream Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) Related to Interest Rate Derivatives	180	1,964	(643)	(18,749)
Debt Hedging | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) Related to Interest Rate Derivatives	(966)	(7,254)	(1,958)	19,352
Debt Hedging | Term Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to term borrowings	$ 941	$ 7,152	$ 1,870	$ (19,059)