SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Stock-Based Compensation (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) Plan $ / shares shares	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares
Share-Based Compensation [Abstract]
Number of stock based compensation plans | Plan	1
Additional Disclosures [Abstract]
Proceeds from stock option exercises	$ 58,420	$ 132,400
Closing price of common stock (in dollars per share) | $ / shares	$ 62.33
General and Administrative [Member]
Share Based Compensation Expense [Abstract]
Stock-based compensation expense	$ 142,000	33,000
Stock Options [Member]
Stock Options Activity [Roll Forward]
Outstanding, beginning of period (in shares) | shares	175,500
Grants (in shares) | shares	0
Exercised (in shares) | shares	(2,000)
Outstanding, end of period (in shares) | shares	173,500		175,500
Exercisable, end of period (in shares) | shares	92,000
Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 37.73
Grants (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	29.21
Outstanding, end of period (in dollars per share) | $ / shares	37.83		$ 37.73
Exercisable, end of period (in dollars per share) | $ / shares	$ 26.13
Weighted Average Remaining Contractual Term [Roll Forward]
Outstanding	6 years 1 month 20 days		6 years 3 months 29 days
Grants	0 years
Exercised	0 years
Exercisable	3 years 6 months 4 days
Aggregate Intrinsic Value [Roll Forward]
Outstanding, beginning of period	$ 4,014,235
Grants	0
Exercised	66,240
Outstanding, end of period	4,251,610		$ 4,014,235
Exercisable, end of period	3,330,690
Additional Disclosures [Abstract]
Proceeds from stock option exercises	58,420	$ 132,400
Unrecognized compensation cost	$ 1,600
Recognized compensation period	3 years 4 months 20 days