EMPLOYEE BENEFIT PLANS (Nonunion Plan Assets - FV) (Details) - Nonunion Defined Benefit Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension and other postretirement benefit plans
Fair value of plan assets	$ 144,805	$ 136,917	$ 158,265
Cash and Cash Equivalents
Pension and other postretirement benefit plans
Fair value of plan assets	23,696	19,079
Debt Instruments
Pension and other postretirement benefit plans
Fair value of plan assets	36,245	26,662
Floating Rate Loan Fund
Pension and other postretirement benefit plans
Fair value of plan assets	15,687	15,868
Large Cap U.S. Equity
Pension and other postretirement benefit plans
Fair value of plan assets	20,208	23,459
Mid Cap U.S. Equity
Pension and other postretirement benefit plans
Fair value of plan assets	13,597	14,276
Small Cap U.S. Equity
Pension and other postretirement benefit plans
Fair value of plan assets	14,561	14,135
International Equity
Pension and other postretirement benefit plans
Fair value of plan assets	20,811	23,438
Level 1
Pension and other postretirement benefit plans
Fair value of plan assets	108,560	110,255
Level 1 | Cash and Cash Equivalents
Pension and other postretirement benefit plans
Fair value of plan assets	23,696	19,079
Level 1 | Floating Rate Loan Fund
Pension and other postretirement benefit plans
Fair value of plan assets	15,687	15,868
Level 1 | Large Cap U.S. Equity
Pension and other postretirement benefit plans
Fair value of plan assets	20,208	23,459
Level 1 | Mid Cap U.S. Equity
Pension and other postretirement benefit plans
Fair value of plan assets	13,597	14,276
Level 1 | Small Cap U.S. Equity
Pension and other postretirement benefit plans
Fair value of plan assets	14,561	14,135
Level 1 | International Equity
Pension and other postretirement benefit plans
Fair value of plan assets	20,811	23,438
Level 2
Pension and other postretirement benefit plans
Fair value of plan assets	36,245	26,662
Level 2 | Debt Instruments
Pension and other postretirement benefit plans
Fair value of plan assets	$ 36,245	$ 26,662
Level 2 | Corporate debt securities
Pension and other postretirement benefit plans
Percentage of investments in debt instruments	81.00%	74.00%
Level 2 | Mortgage-backed instruments
Pension and other postretirement benefit plans
Percentage of investments in debt instruments	10.00%	17.00%
Level 2 | Treasury instruments
Pension and other postretirement benefit plans
Percentage of investments in debt instruments	7.00%	6.00%
Level 2 | Municipal debt securities
Pension and other postretirement benefit plans
Percentage of investments in debt instruments	1.00%	2.00%
Level 2 | Agency securities
Pension and other postretirement benefit plans
Percentage of investments in debt instruments	1.00%	1.00%