Stockholders' Equity (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax
Accumulated other comprehensive income (loss) beginning balance			$ (775)	$ (662)
Other comprehensive income (loss) before reclassifications			2	(14)
Reclassifications to net earnings			27	30
Total other comprehensive income, net of tax	$ 12	$ 7	29	16
Tax effects reclassified to accumulated deficit			(176)
Accumulated other comprehensive income (loss) ending balance	(922)	(646)	(922)	(646)
Tax provision on net actuarial gain (loss) and prior service costs related to pension and other postretirement benefit plans			10	9
Cumulative Translation Adjustments [Member]
AOCI Attributable to Parent, Net of Tax
Accumulated other comprehensive income (loss) beginning balance			133	159
Other comprehensive income (loss) before reclassifications			2	(14)
Reclassifications to net earnings			0	0
Total other comprehensive income, net of tax			2	(14)
Tax effects reclassified to accumulated deficit			0
Accumulated other comprehensive income (loss) ending balance	135	145	135	145
Net Actuarial Loss and Prior Service Cost [Member]
AOCI Attributable to Parent, Net of Tax
Accumulated other comprehensive income (loss) beginning balance			(908)	(821)
Other comprehensive income (loss) before reclassifications			0	0
Reclassifications to net earnings			27	30
Total other comprehensive income, net of tax			27	30
Tax effects reclassified to accumulated deficit			(176)
Accumulated other comprehensive income (loss) ending balance	$ (1,057)	$ (791)	$ (1,057)	$ (791)