CONSOLIDATED BALANCE SHEET (PARENTHETICALS) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
CURRENT ASSETS:
Allowance for doubtful accounts	$ 126	$ 113
INVESTMENT IN CABLE PROPERTIES:
Property, plant and equipment, accumulated depreciation	$ 20,051	$ 18,077
SHAREHOLDERS' EQUITY:
Preferred stock, par value (dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (shares)	250,000,000	250,000,000
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Treasury stock, shares (shares)	7,506,399	0
Class A Common Stock [Member]
SHAREHOLDERS' EQUITY:
Common stock, par value (dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (shares)	900,000,000	900,000,000
Common stock, shares issued (shares)	239,370,330	238,506,059
Common stock, shares outstanding (shares)	231,863,931	238,506,059
Class B Common Stock [Member]
SHAREHOLDERS' EQUITY:
Common stock, par value (dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (shares)	1,000	1,000
Common stock, shares issued (shares)	1	1
Common stock, shares outstanding (shares)	1	1