STOCK-BASED COMPENSATION - Non-Qualified Stock Option Award Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Outstanding (in shares)	0
Outstanding (in shares)	0	0
Amended and Restated 2010 Equity Incentive Plan | Stock Option Awards
Shares
Outstanding (in shares)	80,000	90,000	113,500
Granted (in shares)	0
Exercised (in shares)	0	(10,000)	(23,500)
Outstanding (in shares)	80,000	80,000	90,000
Exercisable (in shares)	80,000	80,000
Weighted Average Exercise Price (in dollars per share)
Outstanding (in dollars per share)	$ 55.63	$ 52.71	$ 49.03
Exercised (in dollars per share)		29.34	34.95
Outstanding (in dollars per share)	55.63	55.63	$ 52.71
Exercisable (in dollars per share)	$ 55.63	$ 55.63
Weighted Average Remaining Contractual Term
Outstanding	5 years 3 months 4 days
Exercisable	5 years 3 months 4 days	6 years 6 months
Stock-based compensation
Aggregate Intrinsic Value, Outstanding (in dollars)	$ 375,400
Aggregate Intrinsic Value, Exercisable (in dollars)	375,400	$ 25,000
Unrecognized compensation cost (in dollars)	$ 0