CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net earnings (loss)	$ 283	$ 99	$ 505	$ (62)
Other comprehensive income (loss):
Foreign currency translation adjustments	11	(6)	(14)	19
Changes in unamortized actuarial loss, net of tax expense of $6, $8, $30 and $128	19	25	86	398
Changes in unamortized net prior service credit, net of tax expense of $0, $0, $0 and $0	0	0	2	(1)
Total other comprehensive income	30	19	74	416
Total comprehensive income	$ 313	$ 118	$ 579	$ 354