Tax Matters - Reconciliation of Gross Unrecognized Tax Benefits - Footnotes (Details) - USD ($) $ in Millions	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021	[1]	Dec. 31, 2020
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 4,802	[1]	$ 4,494	[1]	$ 6,068		$ 5,595
Income Taxes Payable [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	94		40
Other Current Tax Assets [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	1		3
Noncurrent Deferred Tax Assets and Other Noncurrent Tax Assets [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	1,300		1,200
Noncurrent Deferred Tax Liabilities [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	4		5
Other Taxes Payable [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 3,400		$ 3,200

[1] In 2023, included in Income taxes payable ($94 million), Other current assets ($1 million), Noncurrent deferred tax assets and other noncurrent tax assets ($1.3 billion), Noncurrent deferred tax liabilities ($4 million) and Other taxes payable ($3.4 billion). In 2022, included in Income taxes payable ($40 million), Other current assets ($3 million), Noncurrent deferred tax assets and other noncurrent tax assets ($1.2 billion), Noncurrent deferred tax liabilities ($5 million) and Other taxes payable ($3.2 billion).