v3.10.0.1
Tax Matters - Reconciliation of Gross Unrecognized Tax Benefits - Footnotes (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
 [1]
Dec. 31, 2015
Income Tax Contingency [Line Items]        
Unrecognized tax benefits $ 6,259 [1] $ 6,558 [1] $ 5,826 $ 5,919
Income Taxes Payable [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits 11 1    
Noncurrent Deferred Tax Assets And Other Noncurrent Tax Assets [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits 47 123    
Noncurrent Deferred Tax Liabilities [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits 3,200 3,300    
Other Taxes Payable [Member]        
Income Tax Contingency [Line Items]        
Unrecognized tax benefits $ 3,000 $ 3,200    
[1] In 2018, included in Income taxes payable ($11 million), Current tax assets ($1 million), Noncurrent deferred tax assets and other noncurrent tax assets ($47 million), Noncurrent deferred tax liabilities ($3.2 billion) and Other taxes payable ($3.0 billion). In 2017, included in Income taxes payable ($1 million), Noncurrent deferred tax assets and other noncurrent tax assets ($123 million), Noncurrent deferred tax liabilities ($3.3 billion) and Other taxes payable ($3.2 billion).