SECURITIES (Amortized Cost And Estimated Fair Value Of Available-For-Sale Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
SECURITIES [Abstract]
Maturing in one year or less, Amortized Cost	$ 569,032
Maturing after one year through five years, Amortized Cost	1,347,399
Maturing after five years through ten years, Amortized Cost	45,459
Maturing after ten years, Amortized Cost	231,530
Mortgage-backed securities, Amortized Cost	337,982
Amortized Cost	2,531,402	$ 2,521,592	$ 1,979,323
Maturing in one year or less, Estimated Fair Value	569,120
Maturing after one year through five years, Estimated Fair Value	1,341,746
Maturing after five years through ten years, Estimated Fair Value	47,804
Maturing after ten years, Estimated Fair Value	244,593
Mortgage-backed securities, Estimated Fair Value	337,624
Estimated Fair Value	$ 2,540,887	$ 2,531,676	$ 2,016,373
Maturing in one year or less, Weighted Average Yield	1.05%
Maturing after one year through five years, Weighted Average Yield	1.37%
Maturing after five years through ten years, Weighted Average Yield	5.90%
Maturing after ten years, Weighted Average Yield	5.47%
Mortgage-backed securities, Weighted Average Yield	2.18%