AOCL (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (1,603)	$ (1,517)	$ (1,603)	$ (1,517)		$ (1,665)
Other Comprehensive Income (Loss), Net of Tax	(20)	(15)	(62)	(44)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(53)	(56)	(53)	(56)	$ (53)	(56)	$ (57)	$ (57)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1)	1	2	1
Other Comprehensive Income (Loss), Net of Tax	0	1	3	1
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	1	0	1	0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(1,550)	(1,461)	(1,550)	(1,461)	$ (1,570)	$ (1,609)	$ (1,475)	$ (1,504)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	26	18	77	56
Reclassification from AOCI, Current Period, Tax	(6)	(4)	(18)	(13)
Other Comprehensive Income (Loss), Net of Tax	$ 20	$ 14	$ 59	$ 43