Stockholders' Equity Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended								9 Months Ended
		Sep. 30, 2021		Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020		Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		$ 25,625		$ 24,778	$ 25,063	$ 24,801		$ 24,079	$ 24,555	$ 25,063	$ 24,555
Amounts Reclassified from Accumulated Other Comprehensive Loss		(141)				(17)				(444)	12
Other comprehensive (loss) income		(400)		122	(477)	49		88	(663)	(755)	(526)
Ending Balance		24,979		25,625	24,778	24,346		24,801	24,079	24,979	24,346
Accumulated Other Comprehensive Income (Loss), Net of Tax		(3,645)				(3,796)				(3,645)	(3,796)	$ (2,890)
Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Loss) Income, before Reclassifications, Net of Tax										(6)	(10)
Amounts Reclassified from Accumulated Other Comprehensive Loss										32	4
Other comprehensive (loss) income										26	(6)
Accumulated Other Comprehensive Income (Loss), Net of Tax		(1,407)				(1,253)				(1,407)	(1,253)	(1,433)	$ (1,247)
Other Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Loss) Income, before Reclassifications, Net of Tax										1	2
Amounts Reclassified from Accumulated Other Comprehensive Loss										(475)	1
Other comprehensive (loss) income										(474)	3
Accumulated Other Comprehensive Income (Loss), Net of Tax		116				(78)				116	(78)	590	(81)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Loss) Income, before Reclassifications, Net of Tax	[1]									(424)	(507)
Amounts Reclassified from Accumulated Other Comprehensive Loss										0	0
Other comprehensive (loss) income										(424)	(507)
Accumulated Other Comprehensive Income (Loss), Net of Tax		(2,394)				(2,451)				(2,394)	(2,451)	(1,970)	(1,944)
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Loss) Income, before Reclassifications, Net of Tax										115	(23)
Amounts Reclassified from Accumulated Other Comprehensive Loss		5				(19)				(8)	7
Other comprehensive (loss) income										107	(16)
Accumulated Other Comprehensive Income (Loss), Net of Tax		40				(14)				40	(14)	(67)	2
Unrealized Gain (loss) on Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance					(10)				0	(10)	0
Other Comprehensive (Loss) Income, before Reclassifications, Net of Tax										3	0
Amounts Reclassified from Accumulated Other Comprehensive Loss		0	[2]			0	[2]			7	0
Other comprehensive (loss) income										10	0
Ending Balance		0				0				0	0
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(3,245)		(3,367)	(2,890)	(3,845)		(3,933)	(3,270)	(2,890)	(3,270)
Other Comprehensive (Loss) Income, before Reclassifications, Net of Tax										(311)	(538)
Amounts Reclassified from Accumulated Other Comprehensive Loss										(444)	12
Other comprehensive (loss) income		(400)		122	(477)	49		88	(663)	(755)	(526)
Ending Balance		(3,645)		$ (3,245)	$ (3,367)	(3,796)		$ (3,845)	$ (3,933)	(3,645)	(3,796)
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ (3,645)				$ (3,796)				$ (3,645)	$ (3,796)	$ (2,890)	$ (3,270)

[1] The cumulative translation adjustment loss for the nine months ended September 30, 2021 was primarily driven by strengthening of the USD against the European Euro ("EUR"), Swiss Franc ("CHF") and Brazilian Real ("BRL"). The cumulative translation adjustment loss for the nine months ended September 30, 2020 was primarily driven by strengthening of the USD against the Brazilian Real ("BRL") and the South African Rand ("ZAR") against the USD.

[2] Reflected in other income - net in the interim Consolidated Statements of Operations.