Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
NET EARNINGS (LOSS)	$ 33,103	$ (32,884)	$ 73,615	$ (76,622)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	22	(15)	(117)	121
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	33,855	(27,099)	75,686	(68,158)
Pension Plans [Member]
Other comprehensive income (loss), net of tax	687	5,763	2,061	8,232
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	(200)	(3,283)	(600)	(4,689)
Post-Retirement Plans [Member]
Other comprehensive income (loss), net of tax	43	37	127	111
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	(12)	$ (21)	(38)	(63)
Retained Earnings [Member]
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	$ 33,103		$ 73,615	$ (76,622)