EMPLOYEE BENEFIT PLANS - Rollforward (Details) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) $ / shares shares
Stock Options
Employee benefits
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized \| $	$ 0.0
Long Term Incentive Plan
Employee benefits
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized \| $	$ 9.8
Options Exercisable, Number of Options
Balance, December 31, 2018 \| shares	611
Granted \| shares	674,000
Vested \| shares	(427,000)
Balance, December 31, 2019 \| shares	858,000
Options Exercisable, Weighted Average Exercise Price
Balance, December 31, 2018 (in dollars per share)	$ 37.00
Granted (in dollars per share)	39.74
Vested (in dollars per share)	39.33
Forfeited (in dollars per share)	37.69
Balance, December 31, 2019 (in dollars per share)	$ 37.77
Restricted Stock
Employee benefits
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized \| $	$ 3.9
LTIP Units and Restricted Stock, Number Of shares
Balance, December 31, 2018 \| shares	307,000
Granted \| shares	124,000
Vested \| shares	(176,000)
Forfeited \| shares	(7,000)
Balance, December 31, 2019 \| shares	248,000
LTIP Units and Restricted Stock, Weighted Average Fair Value Per Restricted Stock
Balance, December 31, 2018 (in dollars per share)	$ 36.58
Granted (in dollars per share)	38.35
Vested (in dollars per share)	36.61
Forfeited (in dollars per share)	37.73
Balance, December 31, 2019 (in dollars per share)	$ 37.29

Weighted average per share amount of option exercisable forfeited during the period.

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Weighted average per share amount of option exercisable granted during the period.

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Weighted average per share amount of option exercisable vested during the period.

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

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

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

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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