Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Stockholders’ equity-
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	700,000,000	700,000,000
Common stock, shares outstanding (in shares)	544,419,619	543,117,533
Other
Receivables-
Allowance for uncollectible accounts	$ 12	$ 26