Basis of Presentation and Summary of Significant Accounting Policies (Details) $ in Millions, £ in Billions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
|
Oct. 09, 2018
USD ($)
|
Dec. 31, 2018
USD ($)
|
Dec. 31, 2018
GBP (£)
|
Dec. 31, 2018
segment
business
|
|
| 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 | |||
| Sky Limited [Member] | ||||
| Business And Basis Of Presentation [Line Items] | ||||
| Interest in business acquired in acquisition | 100.00% | 100.00% | ||
| Cash consideration transferred by Comcast | $ 39,387 | $ 39,400 | £ 30.2 | |