Shareholders' Equity - (Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (3,778)	$ (2,820)	$ (3,387)
Cumulative effect adjustment	[1]		(638)
Other comprehensive loss, pretax		(603)	(325)	718
Benefit from (provision for) income tax, net		162	5	(151)
Other comprehensive (loss) income, net amount		(441)	(320)	567
Ending balance		(4,219)	(3,778)	(2,820)
Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(71)	(94)	(345)
Cumulative effect adjustment	[1]		(4)
Other comprehensive loss, pretax		97	36	341
Benefit from (provision for) income tax, net		(24)	(9)	(90)
Other comprehensive (loss) income, net amount		73	27	251
Ending balance		2	(71)	(94)
Unrealized Gains (Losses) On Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		0	19	14
Cumulative effect adjustment	[1]		(19)
Other comprehensive loss, pretax		0	0	9
Benefit from (provision for) income tax, net		0	0	(4)
Other comprehensive (loss) income, net amount		0	0	5
Ending balance		0	0	19
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		102	402	69
Cumulative effect adjustment	[1]		0
Other comprehensive loss, pretax		186	(300)	348
Benefit from (provision for) income tax, net		0	0	(15)
Other comprehensive (loss) income, net amount		186	(300)	333
Ending balance		288	102	402
Changes In Retirement Plans' Funded Status
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(3,809)	(3,147)	(3,125)
Cumulative effect adjustment	[1]		(615)
Other comprehensive loss, pretax		(886)	(61)	20
Benefit from (provision for) income tax, net		186	14	(42)
Other comprehensive (loss) income, net amount		(700)	(47)	(22)
Ending balance		$ (4,509)	$ (3,809)	$ (3,147)

[1] Reflects the cumulative effects of ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, and ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which we adopted on January 1, 2018.