EARNINGS PER COMMON SHARE - Anti-dilutive Securities (Details) - shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
EARNINGS PER COMMON SHARE
Total potentially dilutive securities	614,116	691,590
Stock options
EARNINGS PER COMMON SHARE
Total potentially dilutive securities	419,197	433,572
Time Vesting Units
EARNINGS PER COMMON SHARE
Total potentially dilutive securities	88,121	144,560
Financial Performance Units
EARNINGS PER COMMON SHARE
Total potentially dilutive securities	70,397	35,256
Restricted Stock Awards
EARNINGS PER COMMON SHARE
Total potentially dilutive securities	36,401	78,202

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration