STOCK OPTIONS - Schedule of Nonvested 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)	331,560	334,400	334,400
Granted (in shares)	19,000	15,000
Vested (in shares)	(7,000)	(6,000)
Forfeited (in shares)	(16,400)	0
Balance (in shares)	327,160	343,400	331,560	334,400
Weighted-Average Exercise Price
Outstanding at beginning of year (in USD per share)	$ 27.74	$ 25.72	$ 25.72
Granted (in USD per share)	29.80	31.84
Vested (in USD per share)	27.13	23.90
Forfeited (in USD per share)	28.90	0
Balance (in USD per share)	$ 27.81	$ 26.02	$ 27.74	$ 25.72
Weighted-Average Remaining Contractual Life in Years
Outstanding	7 years 7 months 9 days	7 years 9 months	7 years 9 months 7 days	7 years 10 months 28 days
Granted	9 years 10 months 24 days	9 years 10 months 17 days
Vested	7 years 9 months 21 days	8 years 1 month 24 days
Forfeited	8 years 5 months 26 days	8 years 7 months 2 days
Aggregate Intrinsic Value
Outstanding	$ 975	$ 1,673	$ 1,673
Granted	0	26
Vested	22	56
Forfeited	27	0
Outstanding	$ 807	$ 2,508	$ 975	$ 1,673