STOCK-BASED COMPENSATION - Non-Qualified Stock Option Award Activity (Details) - Stock Option Awards	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Shares
Outstanding (in shares)	0
Outstanding (in shares)		0
Exercisable (in shares)		0
Amended and Restated 2010 Equity Incentive Plan
Shares
Outstanding (in shares)	90,000
Granted (in shares)	0
Exercised (in shares)	(10,000)
Outstanding (in shares)	80,000	90,000
Exercisable (in shares)	80,000	73,000
Weighted Average Exercise Price (in dollars per share)
Outstanding (in dollars per share) | $ / shares	$ 52.71
Exercised (in dollars per share) | $ / shares	29.34
Outstanding (in dollars per share) | $ / shares	55.63	$ 52.71
Exercisable (in dollars per share) | $ / shares	$ 55.63	$ 51.94
Weighted Average Remaining Contractual Term
Outstanding	6 years 9 months
Exercisable	6 years 9 months	6 years 10 months 17 days
Stock-based compensation
Aggregate Intrinsic Value, Outstanding (in dollars) | $	$ 532,200
Aggregate Intrinsic Value, Exercisable (in dollars) | $	$ 532,200	$ 843,968