Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
NET EARNINGS	$ 23,488	$ 41,222	$ 29,860
Other comprehensive income (loss), net of tax	0	(4)	(5)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(82)	(336)	(1,059)
OTHER COMPREHENSIVE INCOME (LOSS):
Actuarial gain (loss) for retiree liabilities	18,818	(31,895)	(90,180)
Income tax (expense) or benefit	0	46	37
TOTAL COMPREHENSIVE INCOME (LOSS), net of tax	42,634	25,086	(23,198)
Pension Plans [Member]
Other comprehensive income (loss), net of tax	20,214	(16,111)	(50,119)
OTHER COMPREHENSIVE INCOME (LOSS):
Actuarial gain (loss) for retiree liabilities	18,424	(32,640)	(90,400)
Income tax (expense) or benefit	(11,682)	9,359	28,623
Post-Retirement Plans [Member]
Other comprehensive income (loss), net of tax	(986)	315	(1,875)
OTHER COMPREHENSIVE INCOME (LOSS):
Actuarial gain (loss) for retiree liabilities	394	745	220
Income tax (expense) or benefit	$ 560	$ (180)	$ 1,071