Derivative Instruments (Schedule Of Notional Amounts Of Derivative Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional Amount of Derivatives	$ 2,016,270	$ 1,963,178
Interest Rate Swaps [Member]
Derivative [Line Items]
Notional Amount of Derivatives	1,787,029	1,741,412
Interest Rate Caps [Member]
Derivative [Line Items]
Notional Amount of Derivatives	31,630	31,776
Credit Risk Participation Agreements [Member]
Derivative [Line Items]
Notional Amount of Derivatives	153,219	133,488
Foreign Exchange Contracts [Member]
Derivative [Line Items]
Notional Amount of Derivatives	10,907	11,826
Mortgage Loan Commitments [Member]
Derivative [Line Items]
Notional Amount of Derivatives	16,297	17,110
Mortgage Loan Forward Sale Contracts [Member]
Derivative [Line Items]
Notional Amount of Derivatives	688	2,566
Forward TBA Contracts [Member]
Derivative [Line Items]
Notional Amount of Derivatives	$ 16,500	$ 25,000