INVESTMENTS (Estimated fair values of debt securities available-for-sale by contractual maturity ) (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
U.S. treasuries and government agencies
Estimated Fair Value
Due in one year or less	$ 52,841	$ 69,799
Due after one year through five years	18,052	96,709
Due after five years through ten years	0	0
Due after ten years	97,179	91,987
Estimated Fair Value	168,072	258,495
State and municipal
Estimated Fair Value
Due in one year or less	27,442	33,311
Due after one year through five years	56,893	76,723
Due after five years through ten years	59,014	75,820
Due after ten years	154,231	47,795
Estimated Fair Value	297,580	233,649
Mortgage-Backed and asset-backed
Estimated Fair Value
Due in one year or less	2	852
Due after one year through five years	22,202	7,125
Due after five years through ten years	60,454	55,226
Due after ten years	795,297	507,556
Estimated Fair Value	877,955	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	12,192	9,552
Due after ten years	0	0
Estimated Fair Value	12,192	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	80,285	103,962
Due after one year through five years	97,147	180,557
Due after five years through ten years	131,660	140,598
Due after ten years	1,046,707	647,648
Estimated Fair Value	$ 1,355,799	$ 1,072,765