UNIT-BASED COMPENSATION Table 3 - Summary of Performance Units (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based awards, beginning balance (units)	1,277,480	902,911
Unit-based awards, ending balance (units)	1,456,296	1,277,480	902,911
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance units awarded and outstanding, period start	158,326	80,961	77,014
Performance units awarded	95,969	116,230	39,320
Additional performance units awarded			17,690
Unit-based awards, vested (units)	(80,690)	0	(53,063)
Performance units forfeited	(12,044)	(38,865)
Performance units awarded and outstanding, period end	161,561	158,326	80,961
Unit-based awards, beginning balance (units)	80,690	38,865	35,373
Unit-based awards, granted (units)	74,439	80,690	38,865
Additional unit-based awards, granted (units)			17,690
Unit-based awards, forfeited (units)	0	(38,865)
Unit-based awards, ending balance (units)	74,439	80,690	38,865
Weighted-average grant date fair value, period start	$ 23.43	$ 50.04	$ 31.75
Weighted-average grant date fair value (per unit), granted	28.01	23.43	50.04
Weighted-average grant date fair value of additional units, granted			31.75
Weighted-average grant date fair value, vested	23.43		31.75
Weighted-average grant date fair value, forfeited	0	50.04
Weighted-average grant date fair value, period end	$ 28.01	$ 23.43	$ 50.04

The number of additional grants made during the period on other than stock (or unit) option plans.

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The weighted average fair value at grant date for additional nonvested equity-based awards issued during the period on other than stock (or unit) option plans.

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that were awarded but not necessarily granted, and are outstanding as of the balance sheet date

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Awarded and Forfeited in Period

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The number of units awarded 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 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 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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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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