Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Receivables-
Allowance for uncollectible accounts	$ 159	$ 164
Stockholders’ equity-
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, authorized (in shares)	700,000,000	700,000,000
Common stock, outstanding (in shares)	570,261,104	543,117,533
Other
Receivables-
Allowance for uncollectible accounts	$ 10	$ 26