PENSION AND OTHER POSTRETIREMENT PLANS (Details 5) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Employee benefits
Total plan assets	$ 34,695	$ 27,914	$ 24,562
Carrying Amount | Recurring basis
Employee benefits
Total plan assets	34,695	27,914
Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	21,875	19,588
Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	12,820	8,326
Cash and cash equivalents: | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	2,821	822
Cash and cash equivalents: | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	0	0
Cash and cash equivalents: | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	2,821	822
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
Short term investment funds | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	2,821	822
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	2,821	822
Equity Securities | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	20,368	17,882
Equity Securities | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	20,368	17,882
Equity Securities | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
U.S. Large cap | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	9,587	8,950
U.S. Large cap | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	9,587	8,950
U.S. Large cap | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
U.S. Mid cap/small cap | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	3,131	3,038
U.S. Mid cap/small cap | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	3,131	3,038
U.S. Mid cap/small cap | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
International | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	7,283	5,770
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	7,283	5,770
International | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
Equity blend | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	367	124
Equity blend | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	367	124
Equity blend | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	0	0
Fixed income securities | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	11,506	9,210
Fixed income securities | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	1,507	1,706
Fixed income securities | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	9,999	7,504
Government issues | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	1,634	1,948
Government issues | Quoted Prices In Active Markets for Identical Assets (Level 1) | Recurring basis
Employee benefits
Total plan assets	1,507	1,706
Government issues | Significant Other Observable Inputs (Level 2) | Recurring basis
Employee benefits
Total plan assets	127	242
Corporate bonds | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	2,837	1,795
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	2,837	1,795
Mortgage backed | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	1,007	960
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	1,007	960
High yield bonds and bond funds | Carrying Amount | Recurring basis
Employee benefits
Total plan assets	6,028	4,507
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	$ 6,028	$ 4,507