Supplemental Financial Information (Noncash Investing and Financing Activities)(Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares
Supplemental Financial Information [Line Items]
Capital expenditures incurred but not yet paid	$ 1,300
Dividends payable	$ 742
Dividends payable (in dollars per share) | $ / shares	$ 0.1575
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Capital expenditures incurred but not yet paid	$ 294