LOANS - Categorized by Class and Internally Assigned Risk Grades (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Loans by class categorized by internally assigned risk grades
Total loans	$ 3,268,772	$ 3,098,253
Pass
Loans by class categorized by internally assigned risk grades
Total loans	3,180,905	3,012,960
Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	43,186	42,610
Substandard
Loans by class categorized by internally assigned risk grades
Total loans	44,681	42,683
Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Commercial Real Estate | Mortgage loans
Loans by class categorized by internally assigned risk grades
Total loans	1,373,556	1,293,906
Commercial Real Estate | Mortgage loans | Owner occupied
Loans by class categorized by internally assigned risk grades
Total loans	510,398	472,649
Commercial Real Estate | Mortgage loans | Owner occupied | Pass
Loans by class categorized by internally assigned risk grades
Total loans	480,503	451,264
Commercial Real Estate | Mortgage loans | Owner occupied | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	12,045	1,796
Commercial Real Estate | Mortgage loans | Owner occupied | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	17,850	19,589
Commercial Real Estate | Mortgage loans | Owner occupied | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Commercial Real Estate | Mortgage loans | Non-owner occupied
Loans by class categorized by internally assigned risk grades
Total loans	863,158	821,257
Commercial Real Estate | Mortgage loans | Non-owner occupied | Pass
Loans by class categorized by internally assigned risk grades
Total loans	858,069	808,612
Commercial Real Estate | Mortgage loans | Non-owner occupied | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	2,188	8,056
Commercial Real Estate | Mortgage loans | Non-owner occupied | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	2,901	4,589
Commercial Real Estate | Mortgage loans | Non-owner occupied | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Multi-family | Mortgage loans
Loans by class categorized by internally assigned risk grades
Total loans	585,827	595,280
Multi-family | Mortgage loans | Pass
Loans by class categorized by internally assigned risk grades
Total loans	585,409	595,280
Multi-family | Mortgage loans | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	418	0
Multi-family | Mortgage loans | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Multi-family | Mortgage loans | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Residential real estate mortgage loans | Mortgage loans
Loans by class categorized by internally assigned risk grades
Total loans	519,763	464,264
Residential real estate mortgage loans | Mortgage loans | Residential mortgage
Loans by class categorized by internally assigned risk grades
Total loans	448,515	398,173
Residential real estate mortgage loans | Mortgage loans | Residential mortgage | Pass
Loans by class categorized by internally assigned risk grades
Total loans	438,891	393,029
Residential real estate mortgage loans | Mortgage loans | Residential mortgage | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	8,510	4,854
Residential real estate mortgage loans | Mortgage loans | Residential mortgage | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	1,114	290
Residential real estate mortgage loans | Mortgage loans | Residential mortgage | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Residential real estate mortgage loans | Mortgage loans | Home equity
Loans by class categorized by internally assigned risk grades
Total loans	71,248	66,091
Residential real estate mortgage loans | Mortgage loans | Home equity | Pass
Loans by class categorized by internally assigned risk grades
Total loans	68,480	64,601
Residential real estate mortgage loans | Mortgage loans | Home equity | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	1,594	698
Residential real estate mortgage loans | Mortgage loans | Home equity | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	1,174	792
Residential real estate mortgage loans | Mortgage loans | Home equity | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Commercial, industrial and agricultural loans
Loans by class categorized by internally assigned risk grades
Total loans	645,724	616,003
Commercial, industrial and agricultural loans | Secured
Loans by class categorized by internally assigned risk grades
Total loans	168,540	154,926
Commercial, industrial and agricultural loans | Secured | Pass
Loans by class categorized by internally assigned risk grades
Total loans	147,474	128,729
Commercial, industrial and agricultural loans | Secured | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	5,536	12,637
Commercial, industrial and agricultural loans | Secured | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	15,530	13,560
Commercial, industrial and agricultural loans | Secured | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Commercial, industrial and agricultural loans | Unsecured
Loans by class categorized by internally assigned risk grades
Total loans	477,184	461,077
Commercial, industrial and agricultural loans | Unsecured | Pass
Loans by class categorized by internally assigned risk grades
Total loans	458,526	442,985
Commercial, industrial and agricultural loans | Unsecured | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	12,886	14,553
Commercial, industrial and agricultural loans | Unsecured | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	5,772	3,539
Commercial, industrial and agricultural loans | Unsecured | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Real estate construction and land loans
Loans by class categorized by internally assigned risk grades
Total loans	123,393	107,759
Real estate construction and land loans | Pass
Loans by class categorized by internally assigned risk grades
Total loans	123,089	107,440
Real estate construction and land loans | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Real estate construction and land loans | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	304	319
Real estate construction and land loans | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
Installment/consumer loans
Loans by class categorized by internally assigned risk grades
Total loans	20,509	21,041
Installment/consumer loans | Pass
Loans by class categorized by internally assigned risk grades
Total loans	20,464	21,020
Installment/consumer loans | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	9	16
Installment/consumer loans | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	36	5
Installment/consumer loans | Doubtful
Loans by class categorized by internally assigned risk grades
Total loans	0	0
CNB | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	1,300	400
CNB | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	200	1,600
FNBNY | Special Mention
Loans by class categorized by internally assigned risk grades
Total loans	200	200
FNBNY | Substandard
Loans by class categorized by internally assigned risk grades
Total loans	$ 300	$ 300