SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Stock option information (Details)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Options outstanding
Number (in shares) | shares	899,914
Options exercisable
Number (in shares) | shares	557,620
$10.01 — $20.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	$ 10.01
Exercise price, high end of range (in dollars per share)	$ 20.00
Options outstanding
Number (in shares) | shares	154,200
Weighted average remaining contractual life (in years)	4 years 3 months 14 days
Weighted average exercise price (in dollars per share)	$ 18.79
Options exercisable
Number (in shares) | shares	150,038
Weighted average remaining contractual life (in years)	4 years 3 months 14 days
Weighted average exercise price (in dollars per share)	$ 18.79
$20.01 — $30.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	20.01
Exercise price, high end of range (in dollars per share)	$ 30.00
Options outstanding
Number (in shares) | shares	548,348
Weighted average remaining contractual life (in years)	6 years 2 months 4 days
Weighted average exercise price (in dollars per share)	$ 25.19
Options exercisable
Number (in shares) | shares	324,937
Weighted average remaining contractual life (in years)	5 years 9 months 7 days
Weighted average exercise price (in dollars per share)	$ 25.19
$30.01 — $40.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	30.01
Exercise price, high end of range (in dollars per share)	$ 40.00
Options outstanding
Number (in shares) | shares	68,866
Weighted average remaining contractual life (in years)	6 years 29 days
Weighted average exercise price (in dollars per share)	$ 33.32
Options exercisable
Number (in shares) | shares	21,270
Weighted average remaining contractual life (in years)	5 years 7 months 2 days
Weighted average exercise price (in dollars per share)	$ 33.32
$60.01 — $70.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	60.01
Exercise price, high end of range (in dollars per share)	$ 70.00
Options outstanding
Number (in shares) | shares	58,500
Weighted average remaining contractual life (in years)	1 year 2 months 8 days
Weighted average exercise price (in dollars per share)	$ 60.76
Options exercisable
Number (in shares) | shares	43,875
Weighted average remaining contractual life (in years)	1 year 2 months 8 days
Weighted average exercise price (in dollars per share)	$ 60.76
$80.01 — $90.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	80.01
Exercise price, high end of range (in dollars per share)	$ 90.00
Options outstanding
Number (in shares) | shares	25,000
Weighted average remaining contractual life (in years)	3 years 7 months 6 days
Weighted average exercise price (in dollars per share)	$ 86.69
Options exercisable
Number (in shares) | shares	6,250
Weighted average remaining contractual life (in years)	3 years 7 months 6 days
Weighted average exercise price (in dollars per share)	$ 86.69
$90.01 — $100.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	90.01
Exercise price, high end of range (in dollars per share)	$ 100.00
Options outstanding
Number (in shares) | shares	45,000
Weighted average remaining contractual life (in years)	3 years 2 months 4 days
Weighted average exercise price (in dollars per share)	$ 95.67
Options exercisable
Number (in shares) | shares	11,250
Weighted average remaining contractual life (in years)	3 years 2 months 4 days
Weighted average exercise price (in dollars per share)	$ 95.67