Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (375)
Foreign currency translation adjustment	(23)	$ 28	$ (85)
Amortization of prior service credit cost	(3)	(4)	(4)
Income tax expense on changes in post-retirement benefit plans	(19)	(3)	15
Unrealized gain (loss)	9	(14)	(8)
Reclassification of unrealized gain on derivative hedge agreements into revenue	(3)	12	4
Ending Balance	(413)	(375)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(375)	(336)	(210)
Foreign currency translation adjustment	(22)	27	(83)
Income tax impact on foreign currency translation adjustment	39	9	(12)
Amortization of prior service credit cost	(73)	(83)	(36)
Settlement charge released into other non-operating income (expense), net		9
Income tax expense on changes in postretirement benefit plans			15
Income tax expense on changes in post-retirement benefit plans	(19)	(3)	5
Income tax expense on changes in post-retirement benefit plans	18	16
Income tax impact on amortization of postretirement benefit plan items	(3)	(2)	(3)
Unrealized gain (loss)			(8)
Ending Balance	(413)	(375)	(336)
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(17)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(103)	(121)	(15)
Foreign currency translation adjustment	(22)	27	(83)
Income tax impact on foreign currency translation adjustment	39	9	(12)
Ending Balance	(86)	(103)	(121)
Foreign Currency Translation | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(11)
Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(269)	(214)	(198)
Amortization of prior service credit cost	(73)	(83)	(36)
Settlement charge released into other non-operating income (expense), net		9
Income tax expense on changes in postretirement benefit plans			15
Income tax expense on changes in post-retirement benefit plans	(19)	(3)	5
Income tax expense on changes in post-retirement benefit plans	18	16
Income tax impact on amortization of postretirement benefit plan items	(3)	(2)	(3)
Ending Balance	(330)	(269)	(214)
Postretirement Benefit Plans | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance			(6)
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(3)	(1)	3
Unrealized gain (loss)	9	(14)	(8)
Ending Balance	3	(3)	(1)
Nonoperating Income (Expense) | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Income tax impact on amortization of postretirement benefit plan items	16	8	9
Nonoperating Income (Expense) | Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Income tax impact on amortization of postretirement benefit plan items	16	8	9
Cost of Revenue | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Unrealized gain (loss)			4
Reclassification of unrealized gain on derivative hedge agreements into revenue	1	5
Cost of Revenue | Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Unrealized gain (loss)			$ 4
Reclassification of unrealized gain on derivative hedge agreements into revenue	1	5
Revenue | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Reclassification of unrealized gain on derivative hedge agreements into revenue	(4)	7
Revenue | Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Reclassification of unrealized gain on derivative hedge agreements into revenue	$ (4)	7
Cross Currency Swaps | Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Reclassification of unrealized gain on derivative hedge agreements into revenue