Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net earnings	$ 790,558	$ 262,477	$ 304,768
Other comprehensive income (loss):
Changes in cumulative translation adjustment and other	66,172	(70,590)	(99,933)
Amortization of pension and postretirement items	31,520	29,493	27,731
Income tax expense related to amortization of pension and postretirement items	(11,034)	(10,452)	(9,637)
Amortization of pension and postretirement items, net of tax	20,486	19,041	18,094
Change in net actuarial loss and prior service credit	49,680	(98,092)	(23,979)
Income tax (expense) benefit related to change in net actuarial loss and prior service credit	(9,807)	28,344	13,353
Change in net actuarial loss and prior service credit, net of taxes	39,873	(69,748)	(10,626)
Other comprehensive income (loss), net of taxes	126,531	(121,297)	(92,465)
Comprehensive income	$ 917,089	$ 141,180	$ 212,303