PENSION AND OTHER POSTRETIREMENT PLANS - Amounts Recognized in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amounts recognized in accumulated other comprehensive income
Net amount recognized	$ 8,640	$ 6,775
Pension Benefits
Amounts recognized in accumulated other comprehensive income
Net actuarial loss	10,572	7,997
Prior service cost	(408)	(484)
Net amount recognized	10,164	7,513
SERP Benefits
Amounts recognized in accumulated other comprehensive income
Net actuarial loss	2,083	2,071
Prior service cost	0	0
Net amount recognized	$ 2,083	$ 2,071

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount, after tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount, after tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (j)
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