INVESTMENTS (Amortized Cost and Estimated Fair Values of investment securities Available-For-Sale by Contractual Maturity) (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less	$ 9,400	$ 7,493
Due after one year through five years	156,757	156,953
Due after five years through ten years	267,567	282,468
Due after ten years	339,203	282,708
Total debt securities available for sale	772,927	729,622
Estimated Fair Value
Due in one year or less	9,503	7,541
Due after one year through five years	162,574	162,233
Due after five years through ten years	269,361	282,713
Due after ten years	338,428	279,844
Estimated Fair Value	$ 779,866	$ 732,331