CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts receivable, allowance	$ 118	$ 41
Treasury stock (in shares)	130,720,000	126,893,000
Series A Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	100,000,000	100,000,000
Preferred stock, shares issued (in shares)	1,200,000	0
Preferred stock, shares outstanding (in shares)	1,200,000	0
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized shares (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	12,800,000	12,800,000
Common stock, shares outstanding (in shares)	5,523,000	5,523,000
Treasury stock (in shares)	7,300,000	7,300,000
Common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized shares (in shares)	1,600,000,000	1,600,000,000
Common stock, shares issued (in shares)	259,350,000	256,692,000
Common stock, shares outstanding (in shares)	135,906,000	137,076,000