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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock Option Activity [Abstract]
Outstanding at beginning of period (in shares)			1,066	1,017
Granted (in shares)			220	338
Exercised (in shares)			(256)	(198)
Forfeited (in shares)			(47)	0
Cancelled (in shares)			(22)
Outstanding at end of period (in shares)	961	1,157	961	1,157
Exercisable at end of period (in shares)	504	644	504	644
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)			$ 45.32	$ 37.29
Granted (in dollars per share)			85.23	60.78
Exercised (in dollars per share)			37.16	31.03
Forfeited (in dollars per share)			71.81	0
Cancelled (in dollars per share)			57.48
Outstanding at end of period (in dollars per share)	$ 55.06	$ 45.22	55.06	45.22
Exercisable, end of period (in dollars per share)	$ 40.45	$ 34.29	$ 40.45	$ 34.29
Aggregate intrinsic value, outstanding, beginning of period			$ 41,161	$ 23,927
Aggregate intrinsic value, outstanding, end of period	$ 25,995	$ 37,435	25,995	37,435
Aggregate intrinsic value, exercisable, end of period	$ 20,592	$ 27,857	$ 20,592	$ 27,857
Weighted average remaining contractual term, outstanding			6 years 9 months 18 days	6 years 7 months 6 days
Weighted average remaining contractual term, exercisable			5 years 1 month 6 days	4 years 10 months 24 days
Weighted Average Assumptions [Abstract]
Dividend yield			0.50%	0.50%
Expected volatility			30.00%	34.00%
Risk-free interest rate			1.80%	1.20%
Expected term			4 years 7 months 6 days	5 years
Weighted-average fair value of options granted (in dollars per share)	$ 0	$ 0	$ 23.21	$ 18.45
Total intrinsic value of stock options exercised	$ 3,566	$ 4,423	$ 11,163	$ 6,680