CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable, allowance	$ 41	$ 34
Treasury stock - Common stock, Shares	126,893,000	97,159,000
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, Shares authorized	400,000,000	400,000,000
Common stock, Shares issued	12,799,999	12,799,999
Common stock, Shares outstanding	5,523,452	12,799,999
Treasury stock - Common stock, Shares	7,300,000
Common stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, Shares authorized	1,600,000,000	1,600,000,000
Common stock, Shares issued	256,691,777	231,492,986
Common stock, Shares outstanding	137,075,799	134,334,400