v3.20.4
Tax Matters - Reconciliation of Gross Unrecognized Tax Benefits - Footnotes (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
 [1]
Dec. 31, 2017
Income Tax Contingency [Line Items]        
Unrecognized tax benefits $ 5,595 [1] $ 5,381 [1] $ 6,259 $ 6,558
Income Taxes Payable [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits 34 108    
Noncurrent Deferred Tax Assets And Other Noncurrent Tax Assets [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits 18 51    
Noncurrent Deferred Tax Liabilities [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits 3,000 2,800    
Other Taxes Payable [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits $ 2,500 2,400    
Current Tax Assets [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits   $ 2    
[1] In 2020, included in Income taxes payable ($34 million), Noncurrent deferred tax assets and other noncurrent tax assets ($18 million), Noncurrent deferred tax liabilities ($3.0 billion) and Other taxes payable ($2.5 billion). In 2019, included in Income taxes payable ($108 million), Current tax assets ($2 million), Noncurrent deferred tax assets and other noncurrent tax assets ($51 million), Noncurrent deferred tax liabilities ($2.8 billion) and Other taxes payable ($2.4 billion).