PENSION AND OTHER POSTRETIREMENT PLANS - Financial Assets Measured At Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Employee benefits
Total plan assets	$ 33,874	$ 34,695	$ 27,914
Carrying Amount | Recurring basis
Employee benefits
Total plan assets	33,874	34,695
Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	20,909	21,875
Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	12,965	12,820
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	1,063	2,821
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	1,063	2,821
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	1,063	2,821
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	1,063	2,821
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	18,568	20,368
Equity Securities | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	18,568	20,368
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	9,173	9,587
U.S. Large cap | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	9,173	9,587
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	2,760	3,131
U.S. Mid cap/small cap | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	2,760	3,131
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	6,480	7,283
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	6,480	7,283
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	155	367
Equities blend | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	155	367
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	14,243	11,506
Fixed income securities | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	2,341	1,507
Fixed income securities | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	11,902	9,999
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	2,341	1,634
Government issues | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	2,341	1,507
Government issues | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	127
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	2,098	2,837
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	2,098	2,837
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	1,132	1,007
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	1,132	1,007
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	8,672	6,028
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	8,672	6,028
High yield bonds and bond funds | Significant Unobservable Inputs (Level 3) | Recurring basis
Employee benefits
Total plan assets	$ 0	$ 0