v3.20.4
Debt - Debt Assumed (Details) - USD ($)
Dec. 31, 2020
Oct. 28, 2020
Oct. 06, 2020
Aug. 15, 2020
Jun. 24, 2020
Apr. 09, 2020
Apr. 01, 2020
Dec. 31, 2019
Debt Instrument [Line Items]                
Principal Outstanding $ 54,750,000,000              
Carrying Value 71,125,000,000             $ 24,969,000,000
Sprint                
Debt Instrument [Line Items]                
Fair value             $ 31,797,000,000  
Principal Outstanding 24,605,000,000              
Carrying Value $ 26,740,000,000              
Senior Notes due 2021, 7.250% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             7.25%  
Senior Notes due 2023, 7.875% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             7.875%  
Senior Notes due 2024, 7.125% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             7.125%  
Senior Notes due 2025, 7.625% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             7.625%  
Senior Notes due 2026, 7.625% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             7.625%  
Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             3.36%  
Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             4.738%  
Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             5.152%  
Senior Notes due 2021, 11.500% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage 11.50%              
Senior Notes due 2022, 6.000% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             6.00%  
Senior Notes due 2028, 6.875% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             6.875%  
Senior Notes due 2032, 8.750% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             8.75%  
Accounts receivable facility | Sprint                
Debt Instrument [Line Items]                
Fair value             $ 2,310,000,000  
Principal Outstanding $ 0              
Carrying Value 0              
Other debt | Sprint                
Debt Instrument [Line Items]                
Fair value             464,000,000  
Principal Outstanding 256,000,000              
Carrying Value 240,000,000              
Senior Notes                
Debt Instrument [Line Items]                
Principal Outstanding   $ 4,750,000,000 $ 4,000,000,000.0   $ 4,000,000,000.0 $ 19,000,000,000.0    
Senior Notes | Senior Notes due 2021, 7.250% | Sprint                
Debt Instrument [Line Items]                
Fair value             2,324,000,000  
Principal Outstanding 2,250,000,000              
Carrying Value 2,287,000,000              
Senior Notes | Senior Notes due 2023, 7.875% | Sprint                
Debt Instrument [Line Items]                
Fair value             4,682,000,000  
Principal Outstanding 4,250,000,000              
Carrying Value 4,594,000,000              
Senior Notes | Senior Notes due 2024, 7.125% | Sprint                
Debt Instrument [Line Items]                
Fair value             2,746,000,000  
Principal Outstanding 2,500,000,000              
Carrying Value 2,706,000,000              
Senior Notes | Senior Notes due 2025, 7.625% | Sprint                
Debt Instrument [Line Items]                
Fair value             1,677,000,000  
Principal Outstanding 1,500,000,000              
Carrying Value 1,652,000,000              
Senior Notes | Senior Notes due 2026, 7.625% | Sprint                
Debt Instrument [Line Items]                
Fair value             1,701,000,000  
Principal Outstanding 1,500,000,000              
Carrying Value $ 1,679,000,000              
Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%                
Debt Instrument [Line Items]                
Interest rate, stated percentage 3.36%              
Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360% | Sprint                
Debt Instrument [Line Items]                
Fair value             1,310,000,000  
Principal Outstanding $ 656,000,000           3,500,000,000  
Carrying Value 656,000,000              
Senior Notes | Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738% | Sprint                
Debt Instrument [Line Items]                
Fair value             2,153,000,000  
Principal Outstanding 2,100,000,000              
Carrying Value 2,145,000,000              
Senior Notes | Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152% | Sprint                
Debt Instrument [Line Items]                
Fair value             1,960,000,000  
Principal Outstanding 1,838,000,000           $ 1,800,000,000  
Carrying Value 1,950,000,000              
Senior Notes | Senior Notes due 2020, 7.000%                
Debt Instrument [Line Items]                
Interest rate, stated percentage       7.00%        
Senior Notes | Senior Notes due 2020, 7.000% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             7.00%  
Fair value             $ 1,510,000,000  
Principal Outstanding 0              
Carrying Value 0              
Senior Notes | Senior Notes due 2021, 11.500% | Sprint                
Debt Instrument [Line Items]                
Interest rate, stated percentage             11.50%  
Fair value             $ 1,105,000,000  
Principal Outstanding 1,000,000,000              
Carrying Value 1,057,000,000              
Senior Notes | Senior Notes due 2022, 6.000% | Sprint                
Debt Instrument [Line Items]                
Fair value             2,372,000,000  
Principal Outstanding 2,280,000,000              
Carrying Value 2,346,000,000              
Senior Notes | Senior Notes due 2028, 6.875% | Sprint                
Debt Instrument [Line Items]                
Fair value             2,834,000,000  
Principal Outstanding 2,475,000,000              
Carrying Value 2,808,000,000              
Senior Notes | Senior Notes due 2032, 8.750% | Sprint                
Debt Instrument [Line Items]                
Fair value             $ 2,649,000,000  
Principal Outstanding 2,000,000,000              
Carrying Value $ 2,620,000,000