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

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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 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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Weighted average price of options that were either forfeited or expired.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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STOCK-BASED COMPENSATION (Restricted Stock Awards) (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Unvested, beginning of period (in shares)	657,240
Granted (in shares)	174,114
Vested (in shares)	(249,319)
Forfeited (in shares)	(59,438)
Unvested, end of period (in shares)	522,597	657,240
Weighted Average Grant-Date Fair Value
Unvested, beginning of period (in dollars per share)	$ 54.65
Granted (in dollars per share)	68.82
Vested (in dollars per share)	53.99
Forfeited (in dollars per share)	55.65
Unvested, end of period (in dollars per share)	$ 59.57	$ 54.65
Total unrecognized compensation cost	$ 20.6
Expected to be recognized over a weighted average period	2 years 7 months 6 days
Fair value of awards vested in period	$ 16.8	$ 10.8	$ 7.3
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	5 years