PENSION PLAN AND OTHER BENEFIT PLANS - Amounts Recognized, Assumptions Used, Target and Actual Allocation, Fair Value, Estimated Future Benefit Payments, and Other Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net periodic benefit cost [Abstract]
Service cost	$ 0	$ 0
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	506	(626)	$ (711)
Recognized actuarial loss	300	312	318
Prior service credit	0	0	0
Amortization of prior service benefit	(220)	(220)	(220)
Total before tax effect	$ 586	(534)	215
Unrecognized net gain or loss increase threshold percentage for amortization of obligation (in hundredths)	10.00%
Pension Plan
Amount recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss	$ 8,602	9,352
Prior service cost	0	0
Total before tax effects	8,602	9,352
Accumulated benefit obligation	42,800	39,900
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	1,300	1,522	1,551
Expected return on plan assets	(2,444)	(2,221)	(3,309)
Recognized actuarial loss	213	204	188
Amortization of  prior service cost	0	0	0
Recognized (gain) loss due to settlements	0	0	828
Net periodic cost (benefit)	(931)	(495)	(742)
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	(538)	481	736
Recognized actuarial loss	(213)	(204)	(1,016)
Amortization of prior service benefit	0	0	0
Total before tax effect	(751)	277	(280)
Total recognized in net (benefit) cost and other comprehensive income (loss) (before tax effect)	$ (1,682)	$ (218)	$ (1,022)
Weighted-average assumptions for net periodic cost [Abstract]
Discount rate	3.33%	4.35%	3.74%
Expected return on assets	5.50%	5.50%	7.25%
Discount rate	2.61%	3.33%	4.35%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	100.00%	100.00%
Expected return on assets	5.50%	5.50%	7.25%
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 50,134	$ 45,557	$ 41,476
Estimated benefit payments for each of next five years and aggregate amount expected to be paid [Abstract]
2021	2,273
2022	2,279
2023	2,276
2024	2,283
2025	2,284
2026-2030	11,379
Pension Plan | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	50,134	45,557
Pension Plan | Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	47,541	41,477
Pension Plan | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	2,593	4,080
Pension Plan | Fair Value | Significant Unobservable Inputs (Level 3)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 0	$ 0
Pension Plan | Large-Cap Domestic Equities
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	8.70%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	43.00%	38.00%
Expected return on assets	8.70%
Pension Plan | Large-Cap Domestic Equities | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	20.00%
Pension Plan | Large-Cap Domestic Equities | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	50.00%
Pension Plan | Mid-Cap Domestic Equities
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	9.40%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	2.00%	2.00%
Expected return on assets	9.40%
Pension Plan | Mid-Cap Domestic Equities | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	0.00%
Pension Plan | Mid-Cap Domestic Equities | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	15.00%
Pension Plan | Small-Cap Domestic Equities
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	8.80%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	3.00%	2.00%
Expected return on assets	8.80%
Pension Plan | Small-Cap Domestic Equities | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	0.00%
Pension Plan | Small-Cap Domestic Equities | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	10.00%
Pension Plan | Equity Securities - International Companies
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	5.10%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	3.00%	8.00%
Expected return on assets	5.10%
Pension Plan | Equity Securities - International Companies | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	0.00%
Pension Plan | Equity Securities - International Companies | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	20.00%
Pension Plan | Intermediate Fixed Income
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	4.70%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	45.00%	45.00%
Expected return on assets	4.70%
Pension Plan | Intermediate Fixed Income | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	30.00%
Pension Plan | Intermediate Fixed Income | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	70.00%
Pension Plan | Alternative Assets
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	0.00%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	0.00%	0.00%
Expected return on assets	0.00%
Pension Plan | Alternative Assets | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	0.00%
Pension Plan | Alternative Assets | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	10.00%
Pension Plan | Cash
Weighted-average assumptions for net periodic cost [Abstract]
Expected return on assets	1.30%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	4.00%	5.00%
Expected return on assets	1.30%
Pension Plan | Cash | Minimum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	0.00%
Pension Plan | Cash | Maximum
Target allocations of plan assets [Abstract]
Target allocation, minimum (in hundredths)	20.00%
Pension Plan | Cash | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 2,047	$ 2,210
Pension Plan | Cash | Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	2,047	2,210
Pension Plan | Cash | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Cash | Fair Value | Significant Unobservable Inputs (Level 3)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Equity Securities - U.S. Companies | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	21,716	17,939
Pension Plan | Equity Securities - U.S. Companies | Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	21,716	17,939
Pension Plan | Equity Securities - U.S. Companies | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Equity Securities - U.S. Companies | Fair Value | Significant Unobservable Inputs (Level 3)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Mutual Funds | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	23,778	21,328
Pension Plan | Mutual Funds | Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	23,778	21,328
Pension Plan | Mutual Funds | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Mutual Funds | Fair Value | Significant Unobservable Inputs (Level 3)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | U.S. Treasuries/Government Bonds | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	2,318	3,054
Pension Plan | U.S. Treasuries/Government Bonds | Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | U.S. Treasuries/Government Bonds | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	2,318	3,054
Pension Plan | U.S. Treasuries/Government Bonds | Fair Value | Significant Unobservable Inputs (Level 3)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Corporate bonds and notes | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	275	1,026
Pension Plan | Corporate bonds and notes | Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Pension Plan | Corporate bonds and notes | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	275	1,026
Pension Plan | Corporate bonds and notes | Fair Value | Significant Unobservable Inputs (Level 3)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	0	0
Defined Benefit Health Care Plan
Amount recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss	286	417
Prior service cost	(220)	(440)
Total before tax effects	66	(23)
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	9	16	16
Expected return on plan assets	0	0	0
Recognized actuarial loss	74	105	123
Recognized prior service benefit due to curtailments	0	0	0
Amortization of  prior service cost	(220)	(220)	(220)
Net periodic cost (benefit)	(137)	(99)	(81)
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	(57)	31	22
Recognized actuarial loss	(74)	(105)	(123)
Prior service credit	0	0	0
Amortization of prior service benefit	220	220	220
Total before tax effect	89	146	119
Total recognized in net (benefit) cost and other comprehensive income (loss) (before tax effect)	$ (48)	$ 47	$ 38
Average future working lifetime of active participants	5 years
Weighted-average assumptions for net periodic cost [Abstract]
Discount rate	3.33%	4.35%	3.74%
Discount rate	2.61%	3.33%	4.35%
Health care cost trend: Ultimate (Pre-65/Post 65)			5.00%
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 0	$ 0	$ 0
Estimated benefit payments for each of next five years and aggregate amount expected to be paid [Abstract]
2021	48
2022	35
2023	36
2024	20
2025	19
2026-2030	$ 74
Health care cost trend: Initial			6.50%
Defined Benefit Health Care Plan | Minimum
Weighted-average assumptions for net periodic cost [Abstract]
Health care cost trend rate assumed, next fiscal year	6.95%	6.95%	6.95%
Health care cost trend: Ultimate (Pre-65/Post 65)	4.75%	4.75%	4.75%
Estimated benefit payments for each of next five years and aggregate amount expected to be paid [Abstract]
Health care cost trend: Initial	6.95%	6.95%
Defined Benefit Health Care Plan | Maximum
Weighted-average assumptions for net periodic cost [Abstract]
Health care cost trend rate assumed, next fiscal year	5.45%	5.45%	5.45%
Health care cost trend: Ultimate (Pre-65/Post 65)	4.75%	4.75%	4.75%
Estimated benefit payments for each of next five years and aggregate amount expected to be paid [Abstract]
Health care cost trend: Initial	5.45%	5.45%
Executive Supplemental Pension Plan
Amount recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss	$ 359	$ 283
Prior service cost	0	0
Total before tax effects	359	283
Accumulated benefit obligation	1,300	1,200
Net periodic benefit cost [Abstract]
Service cost	0	0	$ 0
Interest cost	39	49	46
Recognized actuarial loss	13	4	7
Net periodic cost (benefit)	52	53	53
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	89	113	(47)
Recognized actuarial loss	(13)	(4)	(7)
Total before tax effect	76	109	(54)
Total recognized in net (benefit) cost and other comprehensive income (loss) (before tax effect)	$ 128	$ 162	$ (1)
Unrecognized net gain or loss increase threshold percentage for amortization of obligation (in hundredths)	10.00%
Weighted-average assumptions for net periodic cost [Abstract]
Discount rate	3.33%	4.35%	3.74%
Discount rate	2.61%	3.33%	4.35%
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 0	$ 0	$ 0
Estimated benefit payments for each of next five years and aggregate amount expected to be paid [Abstract]
2021	108
2022	106
2023	104
2024	101
2025	97
2026-2030	$ 417