Supplemental Financial Information (Cash, Cash Equivalents and Restricted Cash) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Financial Information [Line Items]
Cash and cash equivalents	$ 5,500	$ 3,814
Restricted cash included in other current assets	42	46
Restricted cash included in other noncurrent assets, net	47	49
Cash, cash equivalents and restricted cash, end of year	5,589	3,909	$ 3,571	$ 3,415
NBCUniversal Media LLC [Member]
Supplemental Financial Information [Line Items]
Cash and cash equivalents	1,424	1,444
Restricted cash included in other noncurrent assets, net	20	20
Cash, cash equivalents and restricted cash, end of year	$ 1,444	$ 1,464	$ 2,377	$ 1,987