Supplemental Financial Information (Summary of Operating Lease Assets and Liabilities Recorded in the Consolidated Balance Sheets) (Details) - Accounting Standards Update 2016-02 [Member] - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Operating lease assets		$ 4,200
Other Noncurrent Assets, Net [Member]
Lessee, Lease, Description [Line Items]
Operating lease assets	$ 4,063
Accrued Expenses and Other Current Liabilities [Member]
Lessee, Lease, Description [Line Items]
Operating lease liabilities, current	685
Other Noncurrent Liabilities [Member]
Lessee, Lease, Description [Line Items]
Operating lease liabilities, noncurrent	3,976
NBCUniversal Media LLC [Member]
Lessee, Lease, Description [Line Items]
Operating lease assets		$ 1,700
NBCUniversal Media LLC [Member] | Other Noncurrent Assets, Net [Member]
Lessee, Lease, Description [Line Items]
Operating lease assets	1,591
NBCUniversal Media LLC [Member] | Accrued Expenses and Other Current Liabilities [Member]
Lessee, Lease, Description [Line Items]
Operating lease liabilities, current	166
NBCUniversal Media LLC [Member] | Other Noncurrent Liabilities [Member]
Lessee, Lease, Description [Line Items]
Operating lease liabilities, noncurrent	$ 1,535