v3.7.0.1
Supplemental Financial Information (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($)
$ in Millions
Mar. 31, 2017
Dec. 31, 2016
Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Unrealized gains (losses) on marketable securities $ 104   $ 2
Deferred gains (losses) on cash flow hedges (7)   (60)
Unrecognized gains (losses) on employee benefit obligations 282   8
Cumulative translation adjustments (37)   (34)
Accumulated other comprehensive income (loss) 342 $ 98 (84)
NBCUniversal Media LLC [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Unrealized gains (losses) on marketable securities 1   0
Deferred gains (losses) on cash flow hedges 9   (19)
Unrecognized gains (losses) on employee benefit obligations 120   3
Cumulative translation adjustments (59)   (52)
Accumulated other comprehensive income (loss) $ 71 $ (135) $ (68)