Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Customer accounts receivable, net of allowance for doubtful accounts	$ 25	$ 24
Equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	100,000,000	100,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	1,500,000,000	1,500,000,000
Common stock, issued (in shares)	633,000,000	631,000,000
Common stock, outstanding (in shares)	558,000,000	561,000,000
Treasury stock (in shares)	75,000,000	70,000,000