STOCKHOLDERS' EQUITY - Restricted Stock and Performance Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Unrecognized compensation cost	$ 17,034	$ 15,475
Period for unrecognized compensation cost to be recognized over	1 year 9 months 18 days
Estimated share-based compensation expense	$ 9,100
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 period (in shares)	138	79
Granted (in shares)	35	67
Vested (in shares)	(20)	(8)
Forfeited (in shares)	(1)	(1)
Non-vested balance as of end of period (in shares)	152	137
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Non-vested balance as of beginning of period (in dollars per share)	$ 80.03	$ 72.75
Granted (in dollars per share)	110.72	84.44
Vested (in dollars per share)	67.59	58.52
Forfeited (in dollars per share)	86.82	76.73
Non-vested balance as of end of period (in dollars per share)	$ 89.22	$ 79.31
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 period (in shares)	70	53
Granted (in shares)	20	33
Vested (in shares)	(8)	(9)
Forfeited (in shares)	(11)	(7)
Non-vested balance as of end of period (in shares)	71	70
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Non-vested balance as of beginning of period (in dollars per share)	$ 81.26	$ 75.61
Granted (in dollars per share)	126.46	81.79
Vested (in dollars per share)	104.15	65.64
Forfeited (in dollars per share)	82.71	60.85
Non-vested balance as of end of period (in dollars per share)	$ 91.99	$ 81.26
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.40%	2.50%
Dividend yield rate	0.50%	0.50%
Expected volatility rate	24.00%	24.00%
Initial TSR	10.90%	(5.90%)
Cliff vest	100.00%

Estimated share-based compensation expense for current fiscal year.

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The initial percentage of total shareholder return.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Percentage of vesting of award under share-based payment arrangement.

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