Segment Information - Reconciliation of Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets	$ 263,303	$ 257,143
Operating Segments
Segment Reporting Information [Line Items]
Assets	330,258	311,155
Operating Segments | Wireless
Segment Reporting Information [Line Items]
Assets	253,319	235,873
Operating Segments | Wireline
Segment Reporting Information [Line Items]
Assets	76,939	75,282
Corporate and other
Segment Reporting Information [Line Items]
Assets	240,656	239,040
Eliminations
Segment Reporting Information [Line Items]
Assets	$ (307,611)	$ (293,052)