Other Comprehensive Income (Loss) - Changes in AOCI balance by Component (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Other Comprehensive Income (Loss)
Loss Before Reclassifications	$ (2)
Amounts Reclassified to Net Earnings	27
Tax (Expense) Benefit	(6)
Reclassification of Stranded Tax Effects	(107)
Total Other Comprehensive Loss	(88)
Pension and Other Post-Employment Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(440)
Other Comprehensive Income (Loss)
Loss Before Reclassifications	0
Amounts Reclassified to Net Earnings	31
Tax (Expense) Benefit	(7)
Reclassification of Stranded Tax Effects	(108)
Total Other Comprehensive Loss	(84)
Ending balance	(524)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(46)
Other Comprehensive Income (Loss)
Loss Before Reclassifications	(2)
Amounts Reclassified to Net Earnings	(4)
Tax (Expense) Benefit	1
Reclassification of Stranded Tax Effects	1
Total Other Comprehensive Loss	(4)
Ending balance	(50)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(486)
Other Comprehensive Income (Loss)
Ending balance	$ (574)