Investment Securities (Schedule Of Amortized Cost And Fair Value By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Amortized Cost
Within 1 year	$ 0
After 1 year; within 5 years	0
After 5 years; within 10 years	10,000
After 10 years	0
Subtotal	10,000
Government agency issued MBS and CMO	0
Amortized Cost	10,000	$ 10,000
Fair Value
Within 1 year	0
After 1 year; within 5 years	0
After 5 years; within 10 years	9,786
After 10 years	0
Subtotal	9,786
Government agency issued MBS and CMO	0
Total	9,786	9,901
Amortized Cost
Within 1 year	15,250
After 1 year; within 5 years	95,255
After 5 years; within 10 years	0
After 10 years	6,434
Subtotal	116,939
Government agency issued MBS and CMO	4,744,454
Amortized Cost	4,861,393
Fair Value
Within 1 year	15,042
After 1 year; within 5 years	95,321
After 5 years; within 10 years	1,360
After 10 years	10,808
Subtotal	122,531
Government agency issued MBS and CMO	4,601,880
Total	$ 4,724,411	$ 5,170,255