Other Comprehensive Income (Loss) - Changes in AOCI balance by Component (Details) - USD ($) $ in Millions	3 Months Ended								6 Months Ended
	Jun. 30, 2020		Mar. 31, 2020		Jun. 30, 2019		Mar. 31, 2019		Jun. 30, 2020
Other Comprehensive Income (Loss)
Income (Loss) Before Reclassifications									$ 3
Amounts Reclassified to Net Earnings									28
Tax Expense									(8)
Total Other Comprehensive Income (Loss)	$ 20		$ 3		$ 4		$ 2		23
Pension and Other Post-Employment Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2019, Net of Tax			(619)						(619)
Other Comprehensive Income (Loss)
Income (Loss) Before Reclassifications									0
Amounts Reclassified to Net Earnings									28
Tax Expense									(6)
Total Other Comprehensive Income (Loss)									22
Balance June 30, 2020, Net of Tax	(597)								(597)
Interest Rate Derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2019, Net of Tax			0						0
Other Comprehensive Income (Loss)
Income (Loss) Before Reclassifications									11
Amounts Reclassified to Net Earnings									0
Tax Expense									(2)
Total Other Comprehensive Income (Loss)									9
Balance June 30, 2020, Net of Tax	9								9
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2019, Net of Tax			(56)						(56)
Other Comprehensive Income (Loss)
Income (Loss) Before Reclassifications									(8)
Amounts Reclassified to Net Earnings									0
Tax Expense									0
Total Other Comprehensive Income (Loss)									(8)
Balance June 30, 2020, Net of Tax	(64)								(64)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance December 31, 2019, Net of Tax			(675)						(675)
Other Comprehensive Income (Loss)
Total Other Comprehensive Income (Loss)	20	[1]	$ 3	[1]	$ 4	[2]	$ 2	[2]
Balance June 30, 2020, Net of Tax	$ (652)								$ (652)

[1] Accumulated Other Comprehensive Loss balances shown above are net of tax. The associated taxes were $183 million and $178 million as of first and second quarters 2020, respectively. For additional information, see Note 11, Other Comprehensive Income.

[2] Accumulated Other Comprehensive Loss balances shown above are net of tax. The associated taxes were $179 million and $177 million as of first and second quarters 2019, respectively. For additional information, see Note 11, Other Comprehensive Income.