Period of time related to S&P 500 Index.

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- Definition

The qualified retirement eligibility age for grants awarded in and after 2017.

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No definition available.

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- Definition

The qualified retirement eligibility number of years of service for grants awarded in and after 2017.

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No definition available.

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- Definition

Share-based Compensation Arrangement By Share-based Payment Award, Original Units Granted, Percent

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No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Number of Shares of Common Stock of Which Instrument is Convertible

+ References

No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Correlation with S&P500

+ References

No definition available.

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- Definition

Period of time related to volatility.

+ References

No definition available.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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- Definition

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

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- Definition

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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- Definition

Amount of cash outflow to satisfy grantee's tax withholding obligation for award under share-based payment arrangement.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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- Definition

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

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- Definition

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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- Definition

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

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Number of shares used to settle grantee's tax withholding obligation for award under share-based payment arrangement.

+ References

No definition available.

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STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense	$ 5.5	$ 4.6	$ 17.2	$ 12.9
Payments for the purchase of shares to satisfy the employee income tax withholdings			$ 5.8	$ 14.1
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of common stock of which unit is convertible (in shares)	1		1
Vesting period			3 years
Qualified retirement eligibility age for grants awarded in and after 2017			55 years
Qualified retirement eligibility number of years of service for grants awarded in and after 2017			10 years
Shares purchased to satisfy the employee income tax withholdings (in shares)			50,661
Payments for the purchase of shares to satisfy the employee income tax withholdings			$ 4.9
Vested (in shares)			156,273
Restricted Stock and Restricted Stock Units \| Director
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period			1 year
Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of common stock of which unit is convertible (in shares)	1		1
Vesting period			3 years
Shares purchased to satisfy the employee income tax withholdings (in shares)			9,982
Payments for the purchase of shares to satisfy the employee income tax withholdings			$ 0.9
Vested (in shares)			29,468
Risk-free interest rate			0.15%
Volatility time period			3 years
Expected volatility			31.80%
Correlation to S&P 500 Index time period			3 years
Correlation with S&P index			0.51
Unrecognized compensation expense	$ 37.5		$ 37.5
Unrecognized compensation expense, period for recognition			2 years
Performance-Based Restricted Stock Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Units ultimately expected to be awarded			0.00%
Performance-Based Restricted Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Units ultimately expected to be awarded			200.00%
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award
Vested (in shares)			139,971