Investment Securities (Schedule Of Amortized Cost And Fair Value By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Within 1 year, Amortized Cost	$ 0
After 1 year; within 5 years, Amortized Cost	100
After 5 years; within 10 years, Amortized Cost	0
After 10 years, Amortized Cost	0
Subtotal, Amortized Cost	100
Within 1 year, Fair Value	0
After 1 year; within 5 years, Fair Value	120
After 5 years; within 10 years, Fair Value	1,464
After 10 years, Fair Value	1,639
Subtotal, Fair Value	3,223
Securities available for sale, Amortized Cost	3,969,657	$ 3,971,435
Securities available-for-sale	3,963,138	3,943,499
Held-to-maturity Securities, Debt Maturities, within 1 Year, Amortized Cost	0
Held-to-maturity Securities, Debt Maturities, after 1 year; within 5 years, Amortized Cost	0
Held-to-maturity Securities, Debt Maturities, after 1 year; within 10 years, Amortized Cost	10,000
Held-to-maturity Securities, Debt Maturities, after 10 years, Amortized Cost	0
Held-to-maturity Securities, Debt Maturities, Subtotal, Amortized Cost	10,000
Held-to-maturity Securities, Debt Maturities, within 1 year, Fair Value	0
Held-to-maturity Securities, Debt Maturities, after 1 year; within 5 years, Fair Value	0
Held-to-maturity Securities, Debt Maturities, after 1 year; within 10 years, Fair Value	9,985
Held-to-maturity Securities, Debt Maturities, after 10 years, Fair Value	0
Held-to-maturity Securities, Debt Maturities, Subtotal, Fair Value	9,985
Securities held to maturity, Amortized cost	10,000	14,347
Held-to-maturity Securities, Fair Value	9,985	14,773
Government Agency Issued MBS And CMO
Schedule of Investments [Line Items]
Securities available for sale, Amortized Cost	3,783,144
Securities available-for-sale	3,773,500
Securities held to maturity, Amortized cost	0
Held-to-maturity Securities, Fair Value	0
Equity and other
Schedule of Investments [Line Items]
Securities available for sale, Amortized Cost	186,413	186,756
Securities available-for-sale	186,415	$ 186,754
Securities held to maturity, Amortized cost	0
Held-to-maturity Securities, Fair Value	$ 0