Commitments and Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) employee	Dec. 31, 2018 USD ($)
Commitment And Contingencies [Line Items]
Operating lease expense inclusive of short-term and variable lease expenses	$ 1,100
Weighted average remaining lease term for operating leases	10 years
Weighted average discount rate used to calculate operating lease liabilities	3.74%
Cash payments for operating leases	$ 914
Carrying value of contractual obligation	1,100
Contractual value of a potential obligation	1,800
NBCUniversal Enterprise [Member]
Commitment And Contingencies [Line Items]
Preferred stock redemption value	$ 725
NBCUniversal Enterprise [Member] | Redeemable Subsidiary Preferred Stock [Member]
Commitment And Contingencies [Line Items]
Redeemable subsidiary preferred stock, put period	30 days
Redeemable subsidiary preferred stock, dividend rate	5.25%
Redeemable subsidiary preferred stock, call period	1 year
NBCUniversal Enterprise [Member] | Redeemable Subsidiary Preferred Stock [Member] | Level 2 [Member]
Commitment And Contingencies [Line Items]
Temporary equity, fair value of redeemable subsidiary preferred stock	$ 749	$ 741
NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Operating lease expense inclusive of short-term and variable lease expenses	$ 443
Weighted average remaining lease term for operating leases	15 years
Weighted average discount rate used to calculate operating lease liabilities	4.06%
Cash payments for operating leases	$ 271
Carrying value of contractual obligation	1,100
Contractual value of a potential obligation	$ 1,800
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitment And Contingencies [Line Items]
Number of employees covered under collective bargaining agreements | employee	9,400
Workforce Subject to Collective Bargaining Arrangements [Member] | NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Number of employees covered under collective bargaining agreements | employee	9,400
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitment And Contingencies [Line Items]
Percentage of full-time equivalent employees covered by collective bargaining agreements that have expired or are schedule to expire during the next year	12.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | NBCUniversal Media LLC [Member]
Commitment And Contingencies [Line Items]
Percentage of full-time equivalent employees covered by collective bargaining agreements that have expired or are schedule to expire during the next year	12.00%
Sky Limited [Member]
Commitment And Contingencies [Line Items]
Future cash payments related to additional contracts determined to be operating leases		$ 804