OTHER COMPREHENSIVE INCOME - RECLASSIFICATION (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Significant amounts reclassified out of each component of AOCI
Interest expense on deposits	$ (2,587)	$ (1,620)	$ (6,790)	$ (4,359)
Interest expense on FHLB advances	(2,383)	(2,664)	(6,618)	(8,590)
Total interest expense	(5,418)	(4,536)	(14,547)	(13,680)
Income tax expense	(5,728)	(4,848)	(20,980)	(18,100)
NET INCOME	10,706	9,828	40,794	35,903
Unrealized loss on cash flow hedge | Reclassification out of Accumulated Other Comprehensive Income
Significant amounts reclassified out of each component of AOCI
Interest expense on deposits	(27)	(42)	(87)	(128)
Interest expense on FHLB advances	(24)	(41)	(88)	(128)
Total interest expense	(51)	(83)	(175)	(256)
Income tax expense	18	29	61	90
NET INCOME	$ (33)	$ (54)	$ (114)	$ (166)