STOCK OPTIONS - Schedule of Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Outstanding at beginning of year (in shares)	537,872	469,044	469,044
Granted (in shares)	19,000	15,000
Exercised (in shares)	(19,172)	0
Forfeited (in shares)	(16,400)	0
Balance (in shares)	521,300	484,044	537,872	469,044
Exercisable
Outstanding (in shares)	194,140	140,644
Weighted-average exercise price (in USD per share)	$ 24.52	$ 23.61
Weighted-average remaining contractual life in years	5 years 4 months 28 days	5 years 8 months 15 days
Aggregate intrinsic value	$ 938	$ 1,364
Weighted-Average Exercise Price
Outstanding at beginning of year (in USD per share)	$ 26.49	$ 25.11	$ 25.11
Granted (in USD per share)	29.80	31.84
Exercised (in USD per share)	25.08	0
Forfeited (in USD per share)	28.90	0
Balance (in USD per share)	$ 26.59	$ 25.32	$ 26.49	$ 25.11
Weighted-Average Remaining Contractual Life in Years
Outstanding	6 years 9 months 14 days	7 years 1 month 28 days	6 years 11 months 15 days	7 years 3 months 25 days
Granted	9 years 10 months 24 days	9 years 10 months 17 days
Exercised	6 years 1 month 20 days
Forfeited	8 years 5 months 26 days
Aggregate Intrinsic Value
Outstanding	$ 2,088	$ 2,623	$ 2,623
Granted	0	26
Exercised	79	0
Forfeited	27	0
Outstanding	$ 1,745	$ 3,872	$ 2,088	$ 2,623