Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Statutory U.S. income tax rate		21.00%	21.00%	35.00%
Tax benefit of Tax Cuts and Jobs Act				$ (1,220)
Deferred income tax provision (benefit) for the effect of changes in non-U.S. and U.S. state tax rates		$ (44)	$ (13)	(1,459)
Income tax payments, net of refunds		349	388	7
Deferred tax liabilities, other		1,400
Accrual for the payment of estimated interest and penalties associated with unrecognized tax benefits		21	21
Tax positions for which the ultimate benefits are highly certain, but for which there is uncertainty about the timing of such benefits		53
Undistributed earnings of foreign subsidiaries		2,200
Two Thousand And Six Financing Entities [Member]
Income Tax Contingency [Line Items]
Deferred tax liabilities, other		884
Two Thousand Seven Monetized Notes [Member]
Income Tax Contingency [Line Items]
Deferred tax liabilities, other		485
Tax Cuts and Jobs Act [Member]
Income Tax Contingency [Line Items]
Tax benefit of Tax Cuts and Jobs Act	$ (36)			(1,454)
Transition tax from Tax Cuts and Jobs Act				$ 231
Income tax expense (benefit) from Tax Cuts and Jobs Act			$ (36)
Secretariat of the Federal Revenue Bureau of Brazil [Member]
Income Tax Contingency [Line Items]
Income tax examination, estimate of possible loss		146
Income tax examination, penalties and interest Expense		$ 387