Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net earnings	$ (10,973)	$ 34,444	$ (7,560)	$ 44,005
Defined benefit pension and other postretirement employee benefits:
Amortization of actuarial loss included in net periodic cost, net of tax of $459, $602, $1,376 and $1,807	1,286	1,687	3,859	5,059
Amortization of prior service credit included in net periodic cost, net of tax of $-, $(110), $- and $(331)	0	(309)	0	(926)
Other comprehensive income (loss), net of tax	1,286	1,378	3,859	4,133
Comprehensive income	$ (9,687)	$ 35,822	$ (3,701)	$ 48,138