LOANS - Loans Evaluated for Impairment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Loans receivable: balance at end of period
Total	$ 2,485,066	$ 2,485,613
Commercial real estate
Loans receivable: balance at end of period
Total	838,546	826,746
Commercial and industrial
Loans receivable: balance at end of period
Total	400,293	379,423
Residential real estate
Loans receivable: balance at end of period
Total	1,127,895	1,155,682
Consumer
Loans receivable: balance at end of period
Total	118,332	123,762
Business Activities Loans
Loans receivable: balance at end of period
Individually evaluated for impairment	15,715	9,647
Collectively evaluated	1,517,610	1,442,983
Total	1,533,325	1,452,630
Business Activities Loans | Commercial real estate
Loans receivable: balance at end of period
Individually evaluated for impairment	9,172	7,604
Collectively evaluated	559,130	526,407
Total	568,302	534,011
Business Activities Loans | Commercial and industrial
Loans receivable: balance at end of period
Individually evaluated for impairment	1,506	626
Collectively evaluated	295,321	267,378
Total	296,827	268,004
Business Activities Loans | Residential real estate
Loans receivable: balance at end of period
Individually evaluated for impairment	4,855	1,404
Collectively evaluated	601,273	590,007
Total	606,128	591,411
Business Activities Loans | Consumer
Loans receivable: balance at end of period
Individually evaluated for impairment	182	13
Collectively evaluated	61,886	59,191
Total	62,068	59,204
Acquired Loans
Loans receivable: balance at end of period
Individually evaluated for impairment	937	1,146
Purchased Credit Impaired	11,619	12,587
Collectively evaluated	939,185	1,019,250
Total	951,741	1,032,983
Acquired Loans | Commercial real estate
Loans receivable: balance at end of period
Individually evaluated for impairment	231	241
Purchased Credit Impaired	8,008	8,655
Collectively evaluated	262,005	283,839
Total	270,244	292,735
Acquired Loans | Commercial and industrial
Loans receivable: balance at end of period
Individually evaluated for impairment	423	571
Purchased Credit Impaired	515	632
Collectively evaluated	102,528	110,216
Total	103,466	111,419
Acquired Loans | Residential real estate
Loans receivable: balance at end of period
Individually evaluated for impairment	283	271
Purchased Credit Impaired	3,069	3,259
Collectively evaluated	518,415	560,741
Total	521,767	564,271
Acquired Loans | Consumer
Loans receivable: balance at end of period
Individually evaluated for impairment	0	63
Purchased Credit Impaired	27	41
Collectively evaluated	56,237	64,454
Total	$ 56,264	$ 64,558