Device Payment Plan Agreement and Wireless Service Receivables - Schedule of Credit Quality Indicators (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Device payment plan agreement receivables, at amortized cost	$ 17,079	$ 19,493
Device payment plan agreement
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6,006
2019	9,217
2018	1,355
Prior to 2018	72
Device payment plan agreement receivables, at amortized cost	16,650
Device payment plan agreement | New customers
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,042
2019	1,360
2018	169
Prior to 2018	43
Device payment plan agreement receivables, at amortized cost	2,614
Device payment plan agreement | Existing customers
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,964
2019	7,857
2018	1,186
Prior to 2018	29
Device payment plan agreement receivables, at amortized cost	$ 14,036