PENSION PLAN - Plan Assets at Fair Value (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	$ 7,096	$ 6,165	$ 5,238
Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	5,677	5,179
Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,419	986
Cash
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	639	247
Cash | Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	639	247
Cash | Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Cash | Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Fixed income
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,419	1,418
Fixed income | Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,419	1,418
Fixed income | Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Fixed income | Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Alternative investments
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,348	925
Alternative investments | Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Alternative investments | Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Alternative investments | Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,348	925
Domestic equities
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,916	2,034
Domestic equities | Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,916	2,034
Domestic equities | Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Domestic equities | Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Foreign equities
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,703	1,480
Foreign equities | Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	1,703	1,480
Foreign equities | Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Foreign equities | Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Real estate investment trusts
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	71	61
Real estate investment trusts | Level I
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Real estate investment trusts | Level II
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	0	0
Real estate investment trusts | Level III
Plan's assets at fair value by level, within the fair value hierarchy
Total assets at fair value	$ 71	$ 61