Basis of Presentation and Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2019 business segment
Business And Basis Of Presentation [Line Items]
Number of primary businesses | business	3
NBCUniversal Media LLC [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments	4
Cable Communications [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments	1
NBCUniversal Segments [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments	4
Sky Limited [Member]
Business And Basis Of Presentation [Line Items]
Number of reportable segments	1