OTHER LONG-TERM LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Long-Term Liabilities [Abstract]
Defined benefit pension plan liabilities	$ 63,579	$ 60,007
Post-retirement medical plan liabilities	21,527	22,740
Environmental liabilities	138,545	142,935
Other	310	429
Other long-term liabilities	$ 223,961	$ 226,111