CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 60	$ 58
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	12,600,000,000	12,600,000,000
Common stock, shares issued (in shares)	4,943,282,000	5,126,201,000
Common stock, shares outstanding (in shares)	4,943,282,000	5,126,201,000