Film and Television Costs (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Film And Television Cost [Line Items]
Amortization of completed film and television production expected to be amortized during the next fiscal year	$ 1,700
Expected amortization percentage of released and unamortized film and television costs during the next three fiscal years	86.00%
Remaining unamortized costs of acquired film and television libraries	$ 475
Expected amortization percentage of unamortized acquired film and television library costs during the next three fiscal years	44.00%
NBCUniversal Media LLC [Member]
Film And Television Cost [Line Items]
Amortization of completed film and television production expected to be amortized during the next fiscal year	$ 1,700
Expected amortization percentage of released and unamortized film and television costs during the next three fiscal years	86.00%
Remaining unamortized costs of acquired film and television libraries	$ 475
Expected amortization percentage of unamortized acquired film and television library costs during the next three fiscal years	44.00%
Maximum [Member]
Film And Television Cost [Line Items]
Amortization period of acquired film and television library costs	20 years
Maximum [Member] | NBCUniversal Media LLC [Member]
Film And Television Cost [Line Items]
Amortization period of acquired film and television library costs	20 years