SHARE-BASED COMPENSATION (Details) - Time-based and performance-based shares - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based compensation
Shares granted	900		238,400
Weighted-average grant date fair value (in dollars per share)	$ 75.07		$ 68.39
Total unrecognized compensation cost	$ 25.8		$ 25.8
Unrecognized compensation cost over weighted-average period to be recognized			1 year 8 months 12 days
Selling, general and administrative expenses
Share-based compensation
Total stock-based compensation cost	$ 4.7	$ 5.9	$ 14.2	$ 12.0

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

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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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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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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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