SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Stock option information (Details)	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Options outstanding
Number (in shares) | shares	1,996,509
Options exercisable
Number (in shares) | shares	1,225,924
Up to $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	480,003	[1]
Weighted average remaining contractual life	1 year 6 months 11 days	[1]
Weighted average exercise price (in dollars per share)	$ 9.14	[1]
Options exercisable
Number (in shares) | shares	480,003	[1]
Weighted average remaining contractual life	1 year 6 months 11 days	[1]
Weighted average exercise price (in dollars per share)	$ 9.14	[1]
$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	298,137	[1]
Weighted average remaining contractual life	7 years 10 months 28 days	[1]
Weighted average exercise price (in dollars per share)	$ 18.74	[1]
Options exercisable
Number (in shares) | shares	101,438	[1]
Weighted average remaining contractual life	7 years 9 months 7 days	[1]
Weighted average exercise price (in dollars per share)	$ 18.65	[1]
$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	916,491	[1]
Weighted average remaining contractual life	5 years 11 months 5 days	[1]
Weighted average exercise price (in dollars per share)	$ 25.74	[1]
Options exercisable
Number (in shares) | shares	520,159	[1]
Weighted average remaining contractual life	3 years 10 months 17 days	[1]
Weighted average exercise price (in dollars per share)	$ 23.79	[1]
$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	109,003	[1]
Weighted average remaining contractual life	7 years 7 months 17 days	[1]
Weighted average exercise price (in dollars per share)	$ 32.46	[1]
Options exercisable
Number (in shares) | shares	43,729	[1]
Weighted average remaining contractual life	4 years 11 months 16 days	[1]
Weighted average exercise price (in dollars per share)	$ 32.83	[1]
$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	[1]
Weighted average remaining contractual life	7 years 11 months 9 days	[1]
Weighted average exercise price (in dollars per share)	$ 49.06	[1]
Options exercisable
Number (in shares) | shares	625	[1]
Weighted average remaining contractual life	7 years 11 months 9 days	[1]
Weighted average exercise price (in dollars per share)	$ 49.06	[1]
$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	[1]
Weighted average remaining contractual life	5 years 2 months 9 days	[1]
Weighted average exercise price (in dollars per share)	$ 60.73	[1]
Options exercisable
Number (in shares) | shares	51,375	[1]
Weighted average remaining contractual life	5 years 2 months 9 days	[1]
Weighted average exercise price (in dollars per share)	$ 60.74	[1]
$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	[1]
Weighted average remaining contractual life	7 years 10 months 10 days	[1]
Weighted average exercise price (in dollars per share)	$ 72.78	[1]
Options exercisable
Number (in shares) | shares	3,125	[1]
Weighted average remaining contractual life	7 years 10 months 10 days	[1]
Weighted average exercise price (in dollars per share)	$ 72.78	[1]
$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	[1]
Weighted average remaining contractual life	7 years 15 days	[1]
Weighted average exercise price (in dollars per share)	$ 85.63	[1]
Options exercisable
Number (in shares) | shares	13,438	[1]
Weighted average remaining contractual life	6 years 5 months 16 days	[1]
Weighted average exercise price (in dollars per share)	$ 84.52	[1]
$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	50,000	[1]
Weighted average remaining contractual life	7 years 2 months 5 days	[1]
Weighted average exercise price (in dollars per share)	$ 95.40	[1]
Options exercisable
Number (in shares) | shares	11,094	[1]
Weighted average remaining contractual life	7 years 1 month 13 days	[1]
Weighted average exercise price (in dollars per share)	$ 94.30	[1]
$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	[1]
Weighted average remaining contractual life	7 years 4 months 13 days	[1]
Weighted average exercise price (in dollars per share)	$ 105.11	[1]
Options exercisable
Number (in shares) | shares	938	[1]
Weighted average remaining contractual life	7 years 4 months 13 days	[1]
Weighted average exercise price (in dollars per share)	$ 105.11	[1]

[1] These options contain market-based components as described above.