SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Information about stock options outstanding (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Options outstanding
Number (in shares) | shares	3,163,125
Options exercisable
Number (in shares) | shares	2,214,051
$0.00 - $10.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	$ 0.00
Exercise price, high end of range (in dollars per share)	$ 10.00
Options outstanding
Number (in shares) | shares	1,575,003
Weighted average remaining contractual life	2 years 6 months 15 days
Weighted average exercise price (in dollars per share)	$ 9.14
Options exercisable
Number (in shares) | shares	1,575,003
Weighted average remaining contractual life	2 years 6 months 15 days
Weighted average exercise price (in dollars per share)	$ 9.14
$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	427,781
Weighted average remaining contractual life	8 years 5 months 9 days
Weighted average exercise price (in dollars per share)	$ 18.23
Options exercisable
Number (in shares) | shares	64,729
Weighted average remaining contractual life	3 years 7 months 28 days
Weighted average exercise price (in dollars per share)	$ 15.08
$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	881,711
Weighted average remaining contractual life	6 years 8 months 23 days
Weighted average exercise price (in dollars per share)	$ 25.68
Options exercisable
Number (in shares) | shares	470,311
Weighted average remaining contractual life	4 years 3 months 26 days
Weighted average exercise price (in dollars per share)	$ 23.21
$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	63,880
Weighted average remaining contractual life	7 years 7 days
Weighted average exercise price (in dollars per share)	$ 32.26
Options exercisable
Number (in shares) | shares	39,880
Weighted average remaining contractual life	5 years 5 months 5 days
Weighted average exercise price (in dollars per share)	$ 33.05
$40.01 - $50.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	40.01
Exercise price, high end of range (in dollars per share)	$ 50.00
Options outstanding
Number (in shares) | shares	5,000
Weighted average remaining contractual life	8 years 11 months 9 days
Weighted average exercise price (in dollars per share)	$ 49.06
Options exercisable
Number (in shares) | shares	313
Weighted average remaining contractual life	8 years 11 months 9 days
Weighted average exercise price (in dollars per share)	$ 49.06
$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	71,000
Weighted average remaining contractual life	6 years 2 months 9 days
Weighted average exercise price (in dollars per share)	$ 60.73
Options exercisable
Number (in shares) | shares	46,469
Weighted average remaining contractual life	6 years 2 months 9 days
Weighted average exercise price (in dollars per share)	$ 60.74
$70.01 - $80.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	70.01
Exercise price, high end of range (in dollars per share)	$ 80.00
Options outstanding
Number (in shares) | shares	25,000
Weighted average remaining contractual life	8 years 10 months 13 days
Weighted average exercise price (in dollars per share)	$ 72.78
Options exercisable
Number (in shares) | shares	1,563
Weighted average remaining contractual life	8 years 10 months 13 days
Weighted average exercise price (in dollars per share)	$ 72.78
$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	40,000
Weighted average remaining contractual life	8 years 15 days
Weighted average exercise price (in dollars per share)	$ 85.63
Options exercisable
Number (in shares) | shares	9,063
Weighted average remaining contractual life	7 years 4 months 13 days
Weighted average exercise price (in dollars per share)	$ 84.35
$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	71,875
Weighted average remaining contractual life	8 years 3 months 29 days
Weighted average exercise price (in dollars per share)	$ 94.31
Options exercisable
Number (in shares) | shares	6,251
Weighted average remaining contractual life	8 years 4 days
Weighted average exercise price (in dollars per share)	$ 94.26
$100.01 - $110.00
Stock options outstanding and exercisable
Exercise price, low end of range (in dollars per share)	101.00
Exercise price, high end of range (in dollars per share)	$ 110.00
Options outstanding
Number (in shares) | shares	1,875
Weighted average remaining contractual life	8 years 4 months 13 days
Weighted average exercise price (in dollars per share)	$ 105.11
Options exercisable
Number (in shares) | shares	469
Weighted average remaining contractual life	8 years 4 months 13 days
Weighted average exercise price (in dollars per share)	$ 105.11