STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS - PSU (Details) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) $ / shares shares
Performance Share Units
Number of Shares
Beginning balance (in shares)		124,709
Granted (in shares)		41,729
Vested (in shares)		(86,710)
Forfeited (in shares)		(282)
Ending balance (in shares)	79,446	79,446
Maximum shares issuable (in shares)		79,446
Weighted-Average Grant Date Fair Value (per unit)
Beginning balance (in dollars per share) \| $ / shares		$ 29.73
Granted (in dollars per share) \| $ / shares		15.44
Vested (in dollars per share) \| $ / shares		24.36
Forfeited (in dollars per share) \| $ / shares		69.00
Ending balance (in dollars per share) \| $ / shares	$ 27.95	$ 27.95
Unrecognized compensation costs \| $	$ 0.8	$ 0.8
Weighted-average period of recognition	1 year 2 months 1 day
Market-based Performance Share Units
Number of Shares
Beginning balance (in shares)		57,668
Granted (in shares)		0
Vested (in shares)		0
Forfeited (in shares)		0
Ending balance (in shares)	57,668	57,668
Maximum shares issuable (in shares)		57,668
Weighted-Average Grant Date Fair Value (per unit)
Beginning balance (in dollars per share) \| $ / shares		$ 60.60
Granted (in dollars per share) \| $ / shares		0
Vested (in dollars per share) \| $ / shares		0
Forfeited (in dollars per share) \| $ / shares		0
Ending balance (in dollars per share) \| $ / shares	$ 60.60	$ 60.60

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

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Number of additional shares authorized for issuance under share-based payment arrangement.

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