Other Comprehensive Income (Loss) - Changes in AOCI balance by Component (Details) - USD ($) $ in Millions		3 Months Ended						9 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019
Other Comprehensive Income (Loss)
Loss Before Reclassifications								$ (5)
Amounts Reclassified to Net Earnings								24
Tax Expense								(6)
Total Other Comprehensive Income (Loss)		$ 7	$ 4	$ 2	$ 7	$ 4	$ (99)	13
Pension and Other Post-Employment Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2018, Net of Tax				(604)				(604)
Other Comprehensive Income (Loss)
Loss Before Reclassifications								0
Amounts Reclassified to Net Earnings								18
Tax Expense								(4)
Total Other Comprehensive Income (Loss)								14
Balance September 30, 2019, Net of Tax		(590)						(590)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2018, Net of Tax				(57)				(57)
Other Comprehensive Income (Loss)
Loss Before Reclassifications								(5)
Amounts Reclassified to Net Earnings								6
Tax Expense								(2)
Total Other Comprehensive Income (Loss)								(1)
Balance September 30, 2019, Net of Tax		(58)						(58)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2018, Net of Tax				(661)				(661)
Other Comprehensive Income (Loss)
Total Other Comprehensive Income (Loss)	[1]	7	$ 4	$ 2	$ 7	$ 4	$ (99)
Balance September 30, 2019, Net of Tax		$ (648)						$ (648)

[1] Accumulated Other Comprehensive Loss balances shown above are net of tax. The associated taxes were $160 million, $158 million, and $156 million as of first, second and third quarters 2018, respectively. For additional information, see Note 12, Other Comprehensive Income.