STOCKHOLDERS' EQUITY, Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Option Activity [Abstract]
Outstanding at beginning of period (in shares)	946	1,066
Granted (in shares)	148	216
Exercised (in shares)	(39)	(108)
Forfeited (in shares)	(1)	(7)
Cancelled (in shares)	(1)	(6)
Outstanding at end of period (in shares)	1,053	1,161
Exercisable at end of period (in shares)	637	644
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 55.44	$ 45.32
Granted (in dollars per share)	74.57	85.38
Exercised (in dollars per share)	32.83	36.57
Forfeited (in dollars per share)	73.49	57.20
Cancelled (in dollars per share)	25.39	58.42
Outstanding at end of period (in dollars per share)	58.98	53.46
Exercisable, end of period (in dollars per share)	$ 48.54	$ 39.62
Aggregate intrinsic value, outstanding, beginning of period	$ 24,714	$ 41,161
Aggregate intrinsic value, outstanding, end of period	24,680	34,272
Aggregate intrinsic value, exercisable, end of period	$ 21,306	$ 27,584
Weighted average remaining contractual term, outstanding	6 years 7 months 6 days	6 years 10 months 24 days
Weighted average remaining contractual term, exercisable	5 years 3 months 18 days	5 years 1 month 6 days
Weighted Average Assumptions [Abstract]
Dividend yield	0.60%	0.50%
Expected volatility	27.00%	30.00%
Risk-free interest rate	2.60%	1.80%
Expected term	4 years 4 months 24 days	4 years 7 months 6 days
Weighted-average fair value of options granted (in dollars per share)	$ 18.62	$ 23.27
Total intrinsic value of stock options exercised	$ 1,825	$ 5,221