PENSION AND OTHER POSTRETIREMENT PLANS - Financial Assets Measured At Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Employee benefits
Total plan assets	$ 39,745	$ 33,874	$ 34,695
Carrying Amount | Recurring basis
Employee benefits
Total plan assets	39,745	33,874
Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	25,050	20,909
Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	14,695	12,965
Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Cash Equivalents | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	1,444	1,063
Cash Equivalents | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
Cash Equivalents | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	1,444	1,063
Cash Equivalents | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Cash | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	0	0
Cash | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
Cash | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
Cash | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Short term investment funds | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	1,444	1,063
Short term investment funds | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
Short term investment funds | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	1,444	1,063
Short term investment funds | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Equity Securities | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	23,026	18,568
Equity Securities | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	23,026	18,568
Equity Securities | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
Equity Securities | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
U.S. Large cap | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	12,097	9,173
U.S. Large cap | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	12,097	9,173
U.S. Large cap | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
U.S. Large cap | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
U.S. Mid cap/small cap | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	4,195	2,760
U.S. Mid cap/small cap | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	4,195	2,760
U.S. Mid cap/small cap | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
U.S. Mid cap/small cap | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
International | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	6,320	6,480
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	6,320	6,480
International | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Equities blend | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	414	155
Equities blend | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	414	155
Equities blend | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
Equities blend | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Fixed income securities | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	15,275	14,243
Fixed income securities | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	2,024	2,341
Fixed income securities | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	13,251	11,902
Fixed income securities | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Government issues | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	2,024	2,341
Government issues | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	2,024	2,341
Government issues | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
Government issues | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Corporate bonds | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	2,926	2,098
Corporate bonds | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
Corporate bonds | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	2,926	2,098
Corporate bonds | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
Mortgage backed | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	1,033	1,132
Mortgage backed | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
Mortgage backed | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	1,033	1,132
Mortgage backed | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	0	0
High yield bonds and bond funds | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	9,292	8,672
High yield bonds and bond funds | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
High yield bonds and bond funds | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	9,292	8,672
High yield bonds and bond funds | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	$ 0	$ 0