SECURITIES (Schedule of Amortized Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale, Amortized Cost
Due in one year or less	$ 1,581
Due after one year through five years	100,951
Due after five years through ten years	176,090
Due after ten years	525,953
Amortized cost, total	804,575
Available-for-sale, Fair Value
Due in one year or less	1,585
Due after one year through five years	100,901
Due after five years through ten years	175,368
Due after ten years	518,656
Fair value, total	796,510
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Due in one year or less	754
Due after one year through five years	4,737
Due after five years through ten years	7,011
Due after ten years	81,705
Held-to-maturity securities, at amortized cost	94,207	$ 94,609
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Due in one year or less	757
Due after one year through five years	4,798
Due after five years through ten years	7,121
Due after ten years	82,418
Held-to-maturity Securities, Fair Value	$ 95,094	$ 94,596