STOCKHOLDERS' EQUITY, Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock Option Activity [Abstract]
Outstanding at beginning of period (in shares)			946	1,066
Granted (in shares)			148	220
Exercised (in shares)			(191)	(256)
Forfeited (in shares)			(2)	(47)
Cancelled (in shares)			(1)	(22)
Outstanding at end of period (in shares)	900	961	900	961
Exercisable at end of period (in shares)	496	504	496	504
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	85.23
Exercised (in dollars per share)			42.74	37.16
Forfeited (in dollars per share)			75.44	71.81
Cancelled (in dollars per share)			28.63	57.48
Outstanding at end of period (in dollars per share)	$ 61.27	$ 55.06	61.27	55.06
Exercisable, end of period (in dollars per share)	$ 49.88	$ 40.45	$ 49.88	$ 40.45
Aggregate intrinsic value, outstanding, beginning of period			$ 24,714	$ 41,161
Aggregate intrinsic value, outstanding, end of period	$ 45,745	$ 25,995	45,745	25,995
Aggregate intrinsic value, exercisable, end of period	$ 30,875	$ 20,592	$ 30,875	$ 20,592
Weighted average remaining contractual term, outstanding			6 years 6 months	6 years 9 months 18 days
Weighted average remaining contractual term, exercisable			5 years 1 month 6 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)	$ 0	$ 0	$ 18.62	$ 23.21
Total intrinsic value of stock options exercised	$ 2,743	$ 3,566	$ 9,943	$ 11,163