REGULATORY CAPITAL REQUIREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Company (consolidated) [Member]
Total capital (to risk weighted assets):
Actual	$ 992,454	$ 886,807
Actual Ratio	14.45%	13.82%
Capital Required for Capital Adequacy	$ 549,297	$ 513,398
For Capital Adequacy Purposes Ratio	8.00%	8.00%
Common Equity Tier One Capital	$ 818,176	$ 718,995
Common Equity tier One Capital to Risk Weighted Assets	11.92%	11.20%
Common Equity Tier One Capital Required for Capital Adequacy	$ 308,980	$ 288,787
Common Equity Tier One Capital for Capitalized Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier 1 capital (to risk weighted assets):
Actual	$ 892,176	$ 789,992
Actual Ratio	12.99%	12.31%
For Capital Adequacy Purposes	$ 411,973	$ 385,049
For Capital Adequacy Purposes Ratio	6.00%	6.00%
Tier 1 capital (to average assets):
Actual	$ 892,176	$ 789,992
Actual Ratio	10.69%	10.04%
For Capital Adequacy Purposes	$ 333,754	$ 314,756
For Capital Adequacy Purposes Ratio	4.00%	4.00%
Bank [Member]
Total capital (to risk weighted assets):
Actual	$ 937,574	$ 846,147
Actual Ratio	13.66%	13.19%
Capital Required for Capital Adequacy	$ 549,036	$ 513,175
For Capital Adequacy Purposes Ratio	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 686,295	$ 641,469
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	10.00%	10.00%
Common Equity Tier One Capital	$ 872,024	$ 784,014
Common Equity tier One Capital to Risk Weighted Assets	12.71%	12.22%
Common Equity Tier One Capital Required for Capital Adequacy	$ 308,833	$ 288,661
Common Equity Tier One Capital for Capitalized Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier 1 Capital to be Well Capitalized	$ 446,092	$ 416,955
Common Equity Tier One Capital to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier 1 capital (to risk weighted assets):
Actual	$ 872,024	$ 784,014
Actual Ratio	12.71%	12.22%
For Capital Adequacy Purposes	$ 411,777	$ 384,881
For Capital Adequacy Purposes Ratio	6.00%	6.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 549,036	$ 513,175
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	8.00%	8.00%
Tier 1 capital (to average assets):
Actual	$ 872,024	$ 784,014
Actual Ratio	10.46%	9.97%
For Capital Adequacy Purposes	$ 333,595	$ 314,630
For Capital Adequacy Purposes Ratio	4.00%	4.00%
To Be Well Capitalized Under Prompt Correction Action Provisions	$ 416,994	$ 393,288
To Be Well Capitalized Under Prompt Correction Action Provisions Ratio	5.00%	5.00%