Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
NET EARNINGS	$ 22,665	$ 15,878
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(5)	(16)
OTHER COMPREHENSIVE INCOME (LOSS):
TOTAL COMPREHENSIVE INCOME, net of tax	25,644	16,591
Pension Plans [Member]
Other comprehensive income (loss), net of tax	2,951	687
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	(931)	(200)
Post-Retirement Plans [Member]
Other comprehensive income (loss), net of tax	33	42
OTHER COMPREHENSIVE INCOME (LOSS):
Income tax (expense) or benefit	$ (10)	$ (13)