STOCKHOLDERS' EQUITY - Restricted Stock and Performance Share Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unrecognized compensation cost related to non-vested shares	$ 11,643	$ 8,565	$ 7,742
Weighted-average period of recognition for unrecognized compensation cost	1 year 6 months
Scenario, Forecast
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Estimated share-based compensation expense for current fiscal year				$ 8,800
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested balance as of beginning of year (in shares)	79	66	102
Granted (in shares)	73	42	21
Vested (in shares)	(8)	(27)	(53)
Forfeited (in shares)	(6)	(2)	(4)
Non-vested balance as of end of year (in shares)	138	79	66
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested balance as of beginning of year (in dollars per share)	$ 72.75	$ 65.66	$ 54.18
Granted (in dollars per share)	85.69	77.50	83.43
Vested (in dollars per share)	58.52	62.74	51.39
Forfeited (in dollars per share)	84.65	74.57	55.45
Non-vested balance as of end of year (in dollars per share)	$ 80.03	$ 72.75	$ 65.66
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested balance as of beginning of year (in shares)	53	39	34
Granted (in shares)	33	32	16
Vested (in shares)	(9)	(15)	0
Forfeited (in shares)	(7)	(3)	(11)
Non-vested balance as of end of year (in shares)	70	53	39
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested balance as of beginning of year (in dollars per share)	$ 75.61	$ 72.62	$ 61.06
Granted (in dollars per share)	81.79	71.27	93.85
Vested (in dollars per share)	65.54	58.78	0
Forfeited (in dollars per share)	60.85	72.55	69.25
Non-vested balance as of end of year (in dollars per share)	$ 81.26	$ 75.61	$ 72.62