ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	$ 759,854
Balance at the end of the period	763,327	$ 759,854
Foreign Currency Translation
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(23,368)	(24,159)
Other comprehensive earnings (loss) before reclassifications	(1,213)	791
Other comprehensive earnings (loss) net of tax	(1,213)	791
Balance at the end of the period	(24,581)	(23,368)
Investments
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	882	(1,516)
Other comprehensive earnings (loss) before reclassifications	1,110	2,372
Reclassifications from accumulated other comprehensive loss		26
Other comprehensive earnings (loss) net of tax	1,110	2,398
Balance at the end of the period	1,992	882
Foreign Currency Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	10	(309)
Other comprehensive earnings (loss) before reclassifications	520	272
Reclassifications from accumulated other comprehensive loss	59	47
Other comprehensive earnings (loss) net of tax	579	319
Balance at the end of the period	589	10
Commodity Derivatives
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	92	(444)
Other comprehensive earnings (loss) before reclassifications	434	70
Reclassifications from accumulated other comprehensive loss	187	466
Other comprehensive earnings (loss) net of tax	621	536
Balance at the end of the period	713	92
Postretirement and Pension Benefits
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	2,139	4,206
Other comprehensive earnings (loss) before reclassifications	356	(914)
Reclassifications from accumulated other comprehensive loss	(1,023)	(1,153)
Other comprehensive earnings (loss) net of tax	(667)	(2,067)
Balance at the end of the period	1,472	2,139
Accumulated Other Comprehensive Earnings ( Loss )
Accumulated other comprehensive earnings (loss), net of tax
Balance at the beginning of the period	(20,245)	(22,222)
Other comprehensive earnings (loss) before reclassifications	1,207	2,591
Reclassifications from accumulated other comprehensive loss	(777)	(614)
Other comprehensive earnings (loss) net of tax	430	1,977
Balance at the end of the period	$ (19,815)	$ (20,245)