SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Stock option information (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Options outstanding
Number (in shares) | shares	1,468,046
Options exercisable
Number (in shares) | shares	926,174
$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	174,784
Weighted average remaining contractual life (in years)	5 years 2 months 5 days
Weighted average exercise price (in dollars per share)	$ 18.79
Options exercisable
Number (in shares) | shares	169,457
Weighted average remaining contractual life (in years)	5 years 2 months 5 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	1,057,212
Weighted average remaining contractual life (in years)	4 years 4 months 21 days
Weighted average exercise price (in dollars per share)	$ 24.44
Options exercisable
Number (in shares) | shares	656,287
Weighted average remaining contractual life (in years)	2 years 3 months 4 days
Weighted average exercise price (in dollars per share)	$ 24.01
$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	107,550
Weighted average remaining contractual life (in years)	6 years 7 months 6 days
Weighted average exercise price (in dollars per share)	$ 34.39
Options exercisable
Number (in shares) | shares	39,055
Weighted average remaining contractual life (in years)	5 years 2 months 27 days
Weighted average exercise price (in dollars per share)	$ 32.79
$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)	2 years 2 months 12 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)	2 years 2 months 12 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)	4 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)	4 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)	4 years 2 months 9 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)	4 years 2 months 9 days
Weighted average exercise price (in dollars per share)	$ 95.67