AOCL (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (1,644)	$ (1,603)	$ (1,644)	$ (1,603)		$ (1,770)
Other Comprehensive Income (Loss), Net of Tax	(22)	(20)	(126)	(62)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(54)	(53)	(54)	(53)	$ (55)	(55)	$ (53)	$ (56)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1	(1)	1	2
Other Comprehensive Income (Loss), Net of Tax	1	0	1	3
Accumulated Foreign Currency Adjustment Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	1	0	1
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(1,590)	(1,550)	(1,590)	(1,550)	$ (1,611)	$ (1,715)	$ (1,570)	$ (1,609)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0	67	0
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0	0	87	0
Other Comprehensive Income (Loss) before Reclassifications, Tax	0	0	(20)	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	27	26	76	77
Reclassification from AOCI, Current Period, Tax	(6)	(6)	(18)	(18)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	21	20	58	59
Other Comprehensive Income (Loss), Net of Tax	$ 21	$ 20	$ 125	$ 59