INVESTMENTS (Amortized Cost and Estimated Fair Values of investment securities Available-For-Sale by Contractual Maturity) (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less	$ 10,821	$ 7,493
Due after one year through five years	173,513	156,953
Due after five years through ten years	244,098	282,468
Due after ten years	320,373	282,708
Total debt securities available for sale	748,805	729,622
Estimated Fair Value
Due in one year or less	10,934	7,541
Due after one year through five years	179,386	162,233
Due after five years through ten years	245,324	282,713
Due after ten years	320,213	279,844
Estimated Fair Value	$ 755,857	$ 732,331