CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Components of AOCI (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (15,347)	$ (4,554)
Net unrealized loss on AFS securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other accumulated comprehensive loss, before tax:	(16,530)	(2,741)
Income taxes related to items of accumulated other comprehensive loss:	3,937	1,030
Net unrealized loss on effective cash flow hedging derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other accumulated comprehensive loss, before tax:	(2,708)	(3,588)
Income taxes related to items of accumulated other comprehensive loss:	644	1,338
Net unrealized loss on post-retirement plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other accumulated comprehensive loss, before tax:	(905)	(946)
Income taxes related to items of accumulated other comprehensive loss:	$ 215	$ 353