Related Party Transactions (Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Receivables, net	$ 10,684	$ 11,104
Film and television costs	8,647	7,837
Other noncurrent assets, net	8,883	5,802
Accounts payable and accrued expenses related to trade creditors	10,198	8,494
Accrued expenses and other current liabilities	10,193	10,721
Long-term debt, less current portion	99,847	107,345
Other noncurrent liabilities	16,853	15,329
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Receivables, net	7,040	7,293
Notes receivable from Comcast, current	4,192	2,054
Film and television costs	7,776	7,292
Note receivable from Comcast, noncurrent	1,101	0
Other noncurrent assets, net	3,444	1,822
Accounts payable and accrued expenses related to trade creditors	1,944	1,933
Accrued expenses and other current liabilities	2,052	2,195
Notes payable to Comcast	91	54
Long-term debt, less current portion	10,574	12,731
Other noncurrent liabilities	6,451	5,177
Comcast and Consolidated Subsidiaries [Member] | NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Receivables, net	533	464
Notes receivable from Comcast, current	4,192	2,054
Film and television costs	21	27
Note receivable from Comcast, noncurrent	1,101	0
Other noncurrent assets, net	71	0
Accounts payable and accrued expenses related to trade creditors	75	78
Accrued expenses and other current liabilities	84	32
Notes payable to Comcast	91	54
Long-term debt, less current portion	158	701
Other noncurrent liabilities	$ 459	$ 410