PENSION AND OTHER POSTRETIREMENT PLANS - Additional Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost
Investments for long-term growth (as a percent)	97.00%
Investments for near-term benefit payments (as a percent)	3.00%
Cumulative historical returns for the S&P 500 index (as a percent)	9.50%
Cumulative historical returns for the long term corporate bonds (as a percent)	5.00%
Pension Benefits
Employee benefits
Accumulated benefit obligation	$ 32,300	$ 27,400
Amortization from accumulated other comprehensive income into net periodic benefit cost over the next fiscal year
Estimated net loss	650
Estimated prior service credit	77
SERP Benefits
Employee benefits
Accumulated benefit obligation	6,000	$ 3,600
Amortization from accumulated other comprehensive income into net periodic benefit cost over the next fiscal year
Estimated net loss	$ 257