v3.20.4
Income Taxes - Narrative (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Apr. 01, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Contingency [Line Items]          
Indirect tax effects excluded $ 144        
Federal and state tax credits 411   $ 331    
Uncertain tax benefit reserves 1,159   514 $ 462 $ 412
Valuation allowance (878)   (129) (210)  
Unrecognized tax benefits that would impact effective tax rate 857   $ 310 $ 263  
Sprint          
Income Tax Contingency [Line Items]          
Deferred tax assets   $ 848      
Federal          
Income Tax Contingency [Line Items]          
Unrecognized tax benefits, net operating loss 3,500        
Operating loss carryforwards 176        
Federal | Research Tax Credit Carryforward          
Income Tax Contingency [Line Items]          
Federal and state tax credits 569        
State          
Income Tax Contingency [Line Items]          
Unrecognized tax benefits, net operating loss 1,500        
Operating loss carryforwards 455        
Foreign Tax Authority          
Income Tax Contingency [Line Items]          
Unrecognized tax benefits, net operating loss 67        
Operating loss carryforwards $ 26