STOCKHOLDERS' EQUITY, Restricted Stock and Performance Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Weighted Average Assumptions [Abstract]
Unrecognized compensation cost related to non-vested shares	$ 13,487	$ 13,329
Weighted-average period of recognition for unrecognized compensation cost	2 years
Estimated share-based compensation expense for current fiscal year	$ 6,600
Restricted Stock [Member]
Non-vested restricted stock [Roll Forward]
Non-vested balance as of beginning of period (in shares)	66	102
Granted (in shares)	36	9
Vested (in shares)	(6)	(14)
Forfeited (in shares)	0	0
Non-vested balance as of end of period (in shares)	96	97
Weighted average grant date fair value [Abstract]
Non-vested balance as of beginning of period (in dollars per share)	$ 65.66	$ 54.18
Granted (in dollars per share)	74.57	85.40
Vested (in dollars per share)	50.32	40.98
Forfeited (in dollars per share)	0	0
Non-vested balance as of end of period (in dollars per share)	$ 70.10	$ 59.12
Performance Shares [Member]
Non-vested restricted stock [Roll Forward]
Non-vested balance as of beginning of period (in shares)	39	34
Granted (in shares)	32	15
Vested (in shares)	(15)	0
Forfeited (in shares)	0	0
Non-vested balance as of end of period (in shares)	56	49
Weighted average grant date fair value [Abstract]
Non-vested balance as of beginning of period (in dollars per share)	$ 72.62	$ 61.06
Granted (in dollars per share)	71.27	93.85
Vested (in dollars per share)	58.78	0
Forfeited (in dollars per share)	0	0
Non-vested balance as of end of period (in dollars per share)	$ 75.47	$ 71.34
Weighted Average Assumptions [Abstract]
Risk-free interest rate	2.40%	1.50%
Dividend yield	0.50%	0.60%
Expected volatility	27.00%	32.00%
Initial TSR	(10.50%)	8.20%
Cliff vest	100.00%