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, 2018	Dec. 31, 2017	Dec. 31, 2016
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	$ 711	$ (1,001)	$ (5,369)
Recognized actuarial loss	318	413	1,595
Prior service credit	0	0	1,101
Amortization of prior service benefit	(220)	(220)	(427)
Total before tax effect	215	1,194	7,638
Pension Plan
Amount recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss	9,075	9,356
Prior service cost	0	0
Total before tax effects	9,075	9,356
Accumulated benefit obligation	36,000	42,200
Net periodic benefit cost [Abstract]
Service cost	0	0	1,047
Interest cost	1,551	1,646	1,883
Expected return on plan assets	(3,309)	(3,144)	(3,019)
Recognized actuarial loss	188	267	1,549
Amortization of prior service cost	0	0	7
Recognized (gain) loss due to settlements	828	0	0
Net periodic cost (benefit)	(742)	(1,231)	1,467
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	736	(1,165)	(5,526)
Recognized actuarial loss	1,016	267	1,549
Amortization of prior service benefit	0	0	(7)
Total before tax effect	(280)	(1,432)	(7,082)
Total recognized in net (benefit) cost and other comprehensive income (loss) (before tax effect)	$ (1,022)	$ (2,663)	$ (5,615)
Unrecognized net gain or loss increase threshold percentage for amortization of obligation (in hundredths)	10.00%
Amounts expected to be recognized in net periodic cost during next fiscal year [Abstract]
Loss recognition	$ 196
Prior service cost recognition	$ 0
Weighted-average assumptions for net periodic cost [Abstract]
Discount rate	3.74%	4.16%	4.39%
Expected long-term rate of return on assets	7.25%	7.75%	7.75%
Assumed rate of future compensation increase			5.00%
Discount rate	4.35%	3.74%	4.16%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	100.00%	100.00%
Expected long-term rate of return on assets	7.25%	7.75%	7.75%
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 41,476	$ 46,672	$ 41,560
Estimated benefit payments for each of next five years and aggregate amount expected to be paid [Abstract]
2019	2,181
2020	2,198
2021	2,212
2022	2,235
2023	2,252
2024-2028	$ 11,331
Pension Plan | Minimum
Effect of a 1% decrease in health care trend rate on:
Evaluation period of expected long-term return on plan assets	3 years
Pension Plan | Maximum
Effect of a 1% decrease in health care trend rate on:
Evaluation period of expected long-term return on plan assets	5 years
Pension Plan | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 41,476	46,672
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	37,962	42,184
Pension Plan | Fair Value | Significant Other Observable Inputs (Level 2)
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	3,514	4,488
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 long-term rate of return on assets	10.30%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	38.00%	40.00%
Expected long-term rate of return on assets	10.30%
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 long-term rate of return on assets	10.60%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	2.00%	6.00%
Expected long-term rate of return on assets	10.60%
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 long-term rate of return on assets	10.80%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	6.00%	7.00%
Expected long-term rate of return on assets	10.80%
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 long-term rate of return on assets	10.30%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	4.00%	13.00%
Expected long-term rate of return on assets	10.30%
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 | Equity Securities - International Companies | Carrying Value
Fair value plan assets by asset class [Abstract]
Fair value of plan assets	$ 0	$ 0
Pension Plan | Equity Securities - International 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	0	0
Pension Plan | Equity Securities - International 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 - International 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 | Intermediate Fixed Income
Weighted-average assumptions for net periodic cost [Abstract]
Expected long-term rate of return on assets	4.70%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	37.00%	29.00%
Expected long-term rate of 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 long-term rate of return on assets	7.50%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	0.00%	0.00%
Expected long-term rate of return on assets	7.50%
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 long-term rate of return on assets	2.50%
Target allocations of plan assets [Abstract]
Percentage of plan assets (in hundredths)	13.00%	5.00%
Expected long-term rate of return on assets	2.50%
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	$ 5,476	$ 2,066
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	5,476	2,066
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	16,244	20,865
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	16,244	20,865
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	16,242	19,253
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	16,242	19,253
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	2,031	2,217
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	2,031	2,217
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	1,483	2,271
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	1,483	2,271
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	491	592
Prior service cost	(661)	(881)
Total before tax effects	(170)	(289)
Net periodic benefit cost [Abstract]
Service cost	0	0	43
Interest cost	16	20	66
Recognized actuarial loss	123	143	20
Recognized prior service benefit due to curtailments	0	0	(337)
Amortization of prior service cost	(220)	(220)	(97)
Net periodic cost (benefit)	(81)	(57)	(305)
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	(22)	(98)	(139)
Recognized actuarial loss	(123)	(143)	(20)
Prior service credit	0	0	(1,101)
Amortization of prior service benefit	220	220	434
Total before tax effect	119	175	(548)
Total recognized in net (benefit) cost and other comprehensive income (loss) (before tax effect)	$ 38	$ 118	$ (853)
Average future working lifetime of active participants	5 years
Amounts expected to be recognized in net periodic cost during next fiscal year [Abstract]
Loss recognition	$ 114
Prior service cost recognition	$ (220)
Weighted-average assumptions for net periodic cost [Abstract]
Discount rate	3.74%	4.16%	4.39%
Discount rate	4.35%	3.74%	4.16%
Health care cost trend rate assumed, next fiscal year		6.50%	6.50%
Health care cost trend: Ultimate (Pre-65/Post 65)	5.00%	5.00%	5.00%
Health care cost trend: Initial	6.50%	6.50%	7.00%
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]
2019	132
2020	81
2021	42
2022	33
2023	33
2024-2028	58
Effect of a 1% increase in health care trend rate on:
Benefit obligation	4	5	2
Total service and interest cost	0	0	0
Effect of a 1% decrease in health care trend rate on:
Benefit obligation	(4)	(6)	(3)
Total service and interest cost	0	0	0
Estimated employer contributions in next fiscal year	$ 132
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%
Health care cost trend: Ultimate (Pre-65/Post 65)	4.75%
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%
Health care cost trend: Ultimate (Pre-65/Post 65)	4.75%
Executive Supplemental Pension Plan
Amount recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss	$ 174	228
Prior service cost	0	0
Total before tax effects	174	228
Accumulated benefit obligation	1,200	1,300
Net periodic benefit cost [Abstract]
Service cost	0	0	43
Interest cost	46	50	51
Recognized actuarial loss	7	3	26
Net periodic cost (benefit)	53	53	120
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): [Abstract]
Net actuarial (gain) loss	47	(66)	(18)
Recognized actuarial loss	(7)	(3)	(26)
Total before tax effect	(54)	63	(8)
Total recognized in net (benefit) cost and other comprehensive income (loss) (before tax effect)	$ (1)	$ 116	$ 112
Unrecognized net gain or loss increase threshold percentage for amortization of obligation (in hundredths)	10.00%
Amounts expected to be recognized in net periodic cost during next fiscal year [Abstract]
Loss recognition	$ 4
Prior service cost recognition	$ 0
Weighted-average assumptions for net periodic cost [Abstract]
Discount rate	3.74%	4.16%	4.39%
Discount rate	4.35%	3.74%	4.16%
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]
2019	109
2020	107
2021	105
2022	103
2023	100
2024-2028	443
Effect of a 1% decrease in health care trend rate on:
Estimated employer contributions in next fiscal year	$ 110