STOCK-BASED COMPENSATION - Combined Restricted Stock Units Activity (Details) - RSUs - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Nonvested, beginning of period (shares)	2,901
Granted (shares)	1,212
Vested (shares)	(1,144)
Forfeited (shares)	(318)
Nonvested, end of period (shares)	2,651	2,901
Expected to vest (shares)	1,938
Weighted- Average Grant-Date Fair Value
Nonvested, beginning of period (dollars per share)	$ 31.97
Granted (dollars per share)	58.52	$ 46.07	$ 25.54
Vested (dollars per share)	31.88
Forfeited (dollars per share)	36.74
Nonvested, end of period (dollars per share)	43.69	$ 31.97
Expected to vest (dollars per share)	$ 44.83
Aggregate Intrinsic Value
Nonvested	$ 126,781
Expected to vest	$ 92,661

Intrinsic value of equity-based compensation awards expected to vest. Excludes stock and unit options.

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- Definition

Number of equity-based compensation awards expected to vest. Excludes stock and unit options.

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No definition available.

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Weighted average grant date fair value of equity-based compensation awards expected to vest. Excludes stock and unit options.

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No definition available.

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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

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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- Definition

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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- Definition

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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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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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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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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-Publisher FASB
-Name Accounting Standards Codification
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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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- Definition

Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

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No definition available.

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