v3.20.2
Receivables and Expected Credit Losses - Unamortized Imputed Discount and Allowance for Credit Losses (Details) - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Allowance for credit losses and imputed discount, beginning of period $ 460 $ 516 $ 516
Bad debt expense 346 144  
Write-offs, net of recoveries (152) (164)  
Change in imputed discount on short-term and long-term EIP receivables 10 89  
Impact on the imputed discount from sales of EIP receivables (81) (84)  
Allowance for credit losses and imputed discount, end of period 674 501 460
Beginning balance adjustment due to implementation of the new credit loss standard      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Allowance for credit losses and imputed discount, beginning of period 91    
Allowance for credit losses and imputed discount, end of period     91
Accounts Receivable Allowance      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Allowance for credit losses and imputed discount, beginning of period 61 67 67
Bad debt expense 178 31  
Write-offs, net of recoveries (56) (37)  
Allowance for credit losses and imputed discount, end of period 183 61 61
Accounts Receivable Allowance | Beginning balance adjustment due to implementation of the new credit loss standard      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Allowance for credit losses and imputed discount, beginning of period $ 0    
Allowance for credit losses and imputed discount, end of period     $ 0
EIP Receivables Allowance      
Financing Receivable, Allowance for Credit Loss [Line Items]      
Weighted average effective imputed interest rate (percentage) 7.70%   8.80%
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Allowance for credit losses and imputed discount, beginning of period $ 399 449 $ 449
Bad debt expense 168 113  
Write-offs, net of recoveries (96) (127)  
Change in imputed discount on short-term and long-term EIP receivables 10 89  
Impact on the imputed discount from sales of EIP receivables (81) (84)  
Allowance for credit losses and imputed discount, end of period 491 $ 440 399
EIP Receivables Allowance | Beginning balance adjustment due to implementation of the new credit loss standard      
Financing Receivable, Allowance for Credit Loss [Roll Forward]      
Allowance for credit losses and imputed discount, beginning of period $ 91    
Allowance for credit losses and imputed discount, end of period     $ 91