SHARE-BASED COMPENSATION (Additional Stock Option Information) (Details) - Stock Options - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation
Intrinsic value of options exercised	$ 3.3	$ 4.6	$ 10.2
Cash received from the exercise of options	3.7	3.2	9.0
Fair value of shares vested	2.9	2.6	2.2
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	0.8	$ 1.1	$ 2.6
Unrecognized compensation cost related to nonvested share-based compensation	$ 0.9
Unrecognized compensation cost, recognized over a weighted-average period	1 year 6 months 10 days

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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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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