INVESTMENTS (Estimated fair values of debt securities available-for-sale by contractual maturity ) (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
U.S. treasuries and government agencies
Estimated Fair Value
Due in one year or less	$ 68,673	$ 69,799
Due after one year through five years	25,074	96,709
Due after five years through ten years	0	0
Due after ten years	86,597	91,987
Estimated Fair Value	180,344	258,495
State and municipal
Estimated Fair Value
Due in one year or less	25,296	33,311
Due after one year through five years	66,226	76,723
Due after five years through ten years	72,676	75,820
Due after ten years	112,251	47,795
Estimated Fair Value	276,449	233,649
Mortgage-Backed and asset-backed
Estimated Fair Value
Due in one year or less	0	852
Due after one year through five years	4,413	7,125
Due after five years through ten years	52,349	55,226
Due after ten years	661,720	507,556
Estimated Fair Value	718,482	570,759
Corporate Debt
Estimated Fair Value
Due in one year or less	0	0
Due after one year through five years	0	0
Due after five years through ten years	12,332	9,552
Due after ten years	0	0
Estimated Fair Value	12,332	9,552
Trust Preferred
Estimated Fair Value
Due in one year or less	0	0
Due after one year through five years	0	0
Due after five years through ten years	0	0
Due after ten years	0	310
Estimated Fair Value	0	310
Debt Securities
Estimated Fair Value
Due in one year or less	93,969	103,962
Due after one year through five years	95,713	180,557
Due after five years through ten years	137,357	140,598
Due after ten years	860,568	647,648
Estimated Fair Value	$ 1,187,607	$ 1,072,765