v3.7.0.1
Significant Transactions (Preliminary Allocation of Purchase Price) (Details) - USD ($)
$ in Millions
Aug. 22, 2016
Mar. 31, 2017
Dec. 31, 2016
Business Acquisition [Line Items]      
Goodwill   $ 36,592 $ 35,980
NBCUniversal Media LLC [Member]      
Business Acquisition [Line Items]      
Goodwill   $ 23,793 $ 23,323
DreamWorks Animation [Member]      
Business Acquisition [Line Items]      
Film and television costs $ 854    
Intangible assets 362    
Working capital 232    
Debt (381)    
Tax receivable agreement (146)    
Deferred income taxes 293    
Other noncurrent assets and liabilities and other 114    
Identifiable net assets (liabilities) acquired 1,328    
Noncontrolling interest (337)    
Goodwill 2,782    
Cash consideration transferred by Comcast 3,773    
DreamWorks Animation [Member] | NBCUniversal Media LLC [Member]      
Business Acquisition [Line Items]      
Film and television costs 854    
Intangible assets 362    
Working capital 232    
Debt (381)    
Tax receivable agreement (146)    
Other noncurrent assets and liabilities and other 407    
Identifiable net assets (liabilities) acquired 1,328    
Noncontrolling interest (337)    
Goodwill 2,782    
Cash consideration transferred by Comcast $ 3,773