Annual report pursuant to Section 13 and 15(d)

EMPLOYEE BENEFIT PLANS - major categories of assets in the Company's pension plan (Details)

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EMPLOYEE BENEFIT PLANS - major categories of assets in the Company's pension plan (Details) - Defined benefit pension plan [Member] - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]        
Fair Value of Plan Assets $ 161,646 $ 134,535 $ 129,719 $ 113,813
U.S. Treasury [Member] | Level 1 Inputs [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Fair Value of Plan Assets 907 398    
Mutual Funds [Member] | Level 1 Inputs [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Fair Value of Plan Assets 142,127 112,131    
Cash and Cash Equivalents [Member] | Level 1 Inputs [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Fair Value of Plan Assets 13,943 16,788    
U.S. Government Agency [Member] | Level 2 Inputs [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Fair Value of Plan Assets 2,078 2,822    
DomesticCorporateDebtSecuritiesMember | Level 2 Inputs [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Fair Value of Plan Assets $ 2,591 $ 2,396