STOCK-BASED COMPENSATION - Summary of restricted stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Non-performance based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares underlying restricted stock	149,583	129,667	191,896	161,443
Weighted-average grant date fair value per share	$ 27.58	$ 28.22	$ 28.33	$ 28.20
Aggregate fair value (in thousands)	$ 4,595
Weighted-average remaining vesting period (years)	1 year 9 months 18 days
Performance-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares underlying restricted stock	2,250	2,250	18,000	18,000
Weighted-average grant date fair value per share	$ 34.40	$ 34.40	$ 34.46	$ 34.46
Aggregate fair value (in thousands)	$ 69
Weighted-average remaining vesting period (years)	2 years 6 months

Weighted average remaining contractual term for equity based awards excluding options vesting term.

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

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- Definition

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.

+ References

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- Definition

Intrinsic value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

No definition available.

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