Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 18	$ 17
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	10,000	10,000
Common stock, shares issued (in shares)	1,069	1,060
Common stock, shares outstanding (in shares)	1,069	1,060

Amount of allowance for credit loss on accounts receivable, classified as current.

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Face amount or stated value per share of common stock.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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