INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for loan losses and off-balance sheet credit exposure	$ 9,309	$ 9,906
Net unrealized losses on securities	4,810	4,650
Compensation and related benefit obligations	2,427	2,508
Purchase accounting fair value adjustments	4,141	7,576
Net change in pension and other post-retirement benefits plans	2,630	2,279
Net operating loss carryforward	4,746	1,997
Other	671	1,119
Total deferred tax assets	28,734	30,035
Deferred tax liabilities:
Pension and SERP expense	(4,559)	(3,915)
Depreciation	(1,163)	(808)
REIT undistributed net income	(2,110)	(2,146)
Net deferred loan costs and fees	(2,206)	(1,406)
Net gain on cash flow hedges	(1,210)	(792)
State and local taxes	(1,468)	(1,255)
Other	(353)	(221)
Total deferred tax liabilities	(13,069)	(10,543)
Net deferred tax asset	$ 15,665	$ 19,492