Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
NET EARNINGS	$ 18,495	$ 23,488	$ 41,222
Other comprehensive income (loss), net of tax	0	0	(4)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	129	(82)	(336)
OTHER COMPREHENSIVE INCOME (LOSS):
Actuarial gain (loss) for retiree liabilities	3,179	18,818	(31,895)
Income tax (expense) or benefit	0	0	46
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	35,341	42,634	25,086
Pension Plans [Member]
Other comprehensive income (loss), net of tax	16,513	20,214	(16,111)
OTHER COMPREHENSIVE INCOME (LOSS):
Actuarial gain (loss) for retiree liabilities	3,116	18,424	(32,640)
Income tax (expense) or benefit	(7,304)	(11,682)	9,359
Post-Retirement Plans [Member]
Other comprehensive income (loss), net of tax	204	(986)	315
OTHER COMPREHENSIVE INCOME (LOSS):
Actuarial gain (loss) for retiree liabilities	63	394	745
Income tax (expense) or benefit	$ (91)	$ 560	$ (180)