Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
NET EARNINGS (LOSS)	$ 64,672	$ (5,591)	$ 186,896	$ 26,988
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	0	0	0	0
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	66,070	(4,841)	191,090	29,238
Pension Plans [Member]
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	1,362	726	4,086	2,178
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	(402)	(215)	(1,206)	(645)
Post-Retirement Plans [Member]
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	36	24	108	72
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	$ (11)	$ (7)	$ (33)	$ (21)