QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
QUARTERLY FINANCIAL DATA (UNAUDITED)
Interest income	$ 43,480	$ 42,589	$ 41,551	$ 41,364	$ 39,960	$ 38,438	$ 36,234	$ 35,217	$ 168,984	$ 149,849	$ 137,716
Interest expense	9,382	8,375	7,622	6,825	6,399	6,093	5,441	4,756	32,204	22,689	16,845
Net interest income	34,098	34,214	33,929	34,539	33,561	32,345	30,793	30,461	136,780	127,160	120,871
Provision for loan losses	400	200	400	800	10,400	1,900	950	800	1,800	14,050	5,550
Net interest income after provision for loan losses	33,698	34,014	33,529	33,739	23,161	30,445	29,843	29,661	134,980	113,110	115,321
Non-interest income (loss)	5,115	4,918	(2,578)	4,113	4,499	4,972	4,509	4,122	11,568	18,102	16,046
Non-interest expense	22,071	31,004	22,507	22,598	29,154	21,271	21,006	20,296	98,180	91,727	77,081
Income before income taxes	16,742	7,928	8,444	15,254	(1,494)	14,146	13,346	13,487	48,368	39,485	54,286
Income tax expense	2,878	1,381	1,701	3,181	5,422	4,703	4,505	4,316	9,141	18,946	18,795
Net income	$ 13,864	$ 6,547	$ 6,743	$ 12,073	$ (6,916)	$ 9,443	$ 8,841	$ 9,171	$ 39,227	$ 20,539	$ 35,491
Basic earnings (loss) per share (in dollars per share)	$ 0.70	$ 0.33	$ 0.34	$ 0.61	$ (0.35)	$ 0.48	$ 0.45	$ 0.47	$ 1.97	$ 1.04	$ 2.01
Diluted earnings (loss) per share (in dollars per share)	$ 0.70	$ 0.33	$ 0.34	$ 0.61	$ (0.35)	$ 0.48	$ 0.45	$ 0.47	$ 1.97	$ 1.04	$ 2.00