CONSOLIDATED BALANCE SHEET (PARENTHETICALS) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Allowance for doubtful accounts	$ 193	$ 217
INVESTMENT IN CABLE PROPERTIES:
Property, plant and equipment, accumulated depreciation	$ 32,520	$ 31,639
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)	11,667,008	0
Class A Common Stock
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)	195,489,213	193,730,992
Common stock, shares outstanding (shares)	183,822,205	193,730,992
Class B Common Stock
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