STOCKHOLDERS' EQUITY, Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock Option Activity [Abstract]
Outstanding at beginning of period (in shares)			946	1,066
Granted (in shares)			148	220
Exercised (in shares)			(152)	(150)
Forfeited (in shares)			(2)	(39)
Cancelled (in shares)			(1)	(19)
Outstanding at end of period (in shares)	939	1,078	939	1,078
Exercisable at end of period (in shares)	534	603	534	603
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)			43.32	32.54
Forfeited (in dollars per share)			75.44	70.57
Cancelled (in dollars per share)			25.39	58.61
Outstanding at end of period (in dollars per share)	$ 60.42	$ 54.10	60.42	54.10
Exercisable, end of period (in dollars per share)	$ 49.19	$ 40.83	$ 49.19	$ 40.83
Aggregate intrinsic value, outstanding, beginning of period			$ 24,714	$ 41,161
Aggregate intrinsic value, outstanding, end of period	$ 35,409	$ 27,001	35,409	27,001
Aggregate intrinsic value, exercisable, end of period	$ 26,142	$ 22,249	$ 26,142	$ 22,249
Weighted average remaining contractual term, outstanding			6 years 7 months 6 days	6 years 7 months 6 days
Weighted average remaining contractual term, exercisable			5 years 3 months 18 days	4 years 8 months 12 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	$ 20.54	$ 18.62	$ 23.21
Total intrinsic value of stock options exercised	$ 5,375	$ 2,375	$ 7,200	$ 7,596