SECURITIES (Amortized Cost And Estimated Fair Value Of Available-For-Sale Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
SECURITIES [Abstract]
Maturing in one year or less, Amortized Cost	$ 595,396
Maturing after one year through five years, Amortized Cost	1,170,245
Maturing after five years through ten years, Amortized Cost	60,417
Maturing after ten years, Amortized Cost	216,209
Mortgage-backed securities, Amortized Cost	311,025
Amortized Cost	2,353,292	$ 2,521,592	$ 2,436,449
Maturing in one year or less, Estimated Fair Value	595,218
Maturing after one year through five years, Estimated Fair Value	1,165,247
Maturing after five years through ten years, Estimated Fair Value	61,041
Maturing after ten years, Estimated Fair Value	227,061
Mortgage-backed securities, Estimated Fair Value	311,400
Estimated Fair Value	$ 2,359,967	$ 2,531,676	$ 2,468,199
Maturing in one year or less, Weighted Average Yield	1.21%
Maturing after one year through five years, Weighted Average Yield	1.40%
Maturing after five years through ten years, Weighted Average Yield	5.94%
Maturing after ten years, Weighted Average Yield	5.13%
Mortgage-backed securities, Weighted Average Yield	2.18%