SHAREHOLDERS' EQUITY - Regulatory Capital Requirements (Details) $ in Thousands		Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Consolidated
Common Equity Tier 1 (to Risk Weighted Assets)
Common Equity Tier 1 Capital		$ 612,703	$ 591,026
Common Equity Tier 1 Capital for Capital Adequacy Purposes		$ 187,814	$ 189,055
Common Equity Tier 1 (to Risk Weighted Assets) Ratios [Abstract]
Common Equity Tier 1 Capital to Risk Weighted Assets		0.1468	0.1407
Common Equity Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted Assets		0.0450	0.0450
Tier 1 Capital (to Risk Weighted Assets)
Tier 1 Capital		$ 671,147	$ 649,465
Tier 1 Capital Required for Capital Adequacy Purposes		$ 250,418	$ 252,073
Tier 1 Capital (to Risk Weighted Assets) Ratios
Tier 1 Capital to Risk Weighted Assets		0.1608	0.1546
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted Assets		0.0600	0.0600
Total Capital (to Risk Weighted Assets)
Total Capital		$ 908,873	$ 774,293
Total Capital Required for Capital Adequacy Purposes		$ 333,891	$ 336,098
Total Capital (to Risk Weighted Assets) Ratios
Total Capital to Risk Weighted Assets		0.2178	0.1843
Total Capital Required for Capital Adequacy Purposes to Risk Weighted Assets		0.0800	0.0800
Tier 1 Capital (to Average Assets)
Tier 1 Capital	[1]	$ 671,147	$ 649,465
Tier 1 Capital Required for Capital Adequacy Purposes	[1]	$ 273,558	$ 255,304
Tier 1 Capital (to Average Assets) Ratios
Tier 1 Capital to Average Assets	[1]	0.0981	0.1018
Tier 1 Capital Required for Capital Adequacy Purposes to Average Assets	[1]	0.0400	0.0400
Bank Only
Common Equity Tier 1 (to Risk Weighted Assets)
Common Equity Tier 1 Capital		$ 768,200	$ 738,311
Common Equity Tier 1 Capital for Capital Adequacy Purposes		187,801	188,992
Common Equity Tier 1 Capital to be Well Capitalized		$ 271,268	$ 272,989
Common Equity Tier 1 (to Risk Weighted Assets) Ratios [Abstract]
Common Equity Tier 1 Capital to Risk Weighted Assets		0.1841	0.1758
Common Equity Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted Assets		0.0450	0.0450
Common Equity Tier 1 Capital Required to be Well Capitalized to Risk Weighted Assets		0.0650	0.0650
Tier 1 Capital (to Risk Weighted Assets)
Tier 1 Capital		$ 768,200	$ 738,311
Tier 1 Capital Required for Capital Adequacy Purposes		250,402	251,989
Tier 1 Capital Required to be Well Capitalized		$ 333,869	$ 335,986
Tier 1 Capital (to Risk Weighted Assets) Ratios
Tier 1 Capital to Risk Weighted Assets		0.1841	0.1758
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted Assets		0.0600	0.0600
Tier 1 Capital Required to be Well Capitalized to Risk Weighted Assets		0.0800	0.0800
Total Capital (to Risk Weighted Assets)
Total Capital		$ 808,675	$ 764,563
Total Capital Required for Capital Adequacy Purposes		333,869	335,986
Total Capital Required to be Well Capitalized		$ 417,336	$ 419,982
Total Capital (to Risk Weighted Assets) Ratios
Total Capital to Risk Weighted Assets		0.1938	0.1820
Total Capital Required for Capital Adequacy Purposes to Risk Weighted Assets		0.0800	0.0800
Total Capital Required to be Well Capitalized to Risk Weighted Assets		0.1000	0.1000
Tier 1 Capital (to Average Assets)
Tier 1 Capital	[1]	$ 768,200	$ 738,311
Tier 1 Capital Required for Capital Adequacy Purposes	[1]	273,432	255,204
Tier 1 Capital Required to be Well Capitalized	[1]	$ 341,790	$ 319,004
Tier 1 Capital (to Average Assets) Ratios
Tier 1 Capital to Average Assets	[1]	0.1124	0.1157
Tier 1 Capital Required for Capital Adequacy Purposes to Average Assets	[1]	0.0400	0.0400
Tier 1 Capital Required to be Well Capitalized to Average Assets	[1]	0.0500	0.0500

[1] Refers to quarterly average assets as calculated in accordance with policies established by bank regulatory agencies.