v3.20.4
Receivables and Expected Credit Losses - EIP Receivables (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
class
segment
Jan. 01, 2020
USD ($)
Dec. 31, 2019
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Portfolio segments | segment 2    
Customer classes | class 2    
Total EIP Receivables, net of unamortized imputed discounts $ 6,213   $ 4,582
Unamortized imputed discount (325)   (299)
EIP receivables, net of unamortized imputed discount 5,888   4,283
Allowance for credit losses (280)   (100)
Equipment installment plan receivables, net 5,608   4,183
Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Allowance for credit losses   $ (91)  
Equipment installment plan receivables, net of allowance for credit losses and imputed discount      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Equipment installment plan receivables, net 3,577   2,600
Equipment installment plan receivables due after one year, net of allowance for credit losses and imputed discount      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Equipment installment plan receivables, net $ 2,031   $ 1,583