Condensed Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Property and equipment - accumulated depreciation	$ 49,943	$ 49,694
Other intangible assets - accumulated amortization	$ 12,371	$ 11,013
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
NBCUniversal Media LLC [Member]
Property and equipment - accumulated depreciation	$ 3,999	$ 3,350
Other intangible assets - accumulated amortization	$ 7,372	$ 6,568
Class A Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	7,500,000,000	7,500,000,000
Common stock, shares issued (in shares)	5,537,118,483	5,614,950,039
Common stock, shares outstanding (in shares)	4,664,327,455	4,742,159,011
Treasury stock (in shares)	872,791,028	872,791,028
Class B Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	9,444,375	9,444,375
Common stock, shares outstanding (in shares)	9,444,375	9,444,375