Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 2	$ 2
Common Stock, Shares Authorized	200,000,000
Common Stock, Shares, Issued	107,035,818	123,547,974
Common Stock, Shares, Outstanding	90,222,524	106,240,030
Treasury Stock, Shares	16,813,294	17,307,944