Stockholders' Equity - Share Repurchases in the Open Market (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended	9 Months Ended
		Jun. 30, 2018	Jun. 30, 2018
Stockholders' Equity Note [Abstract]
Shares repurchased in the open market	[1],[2]	14	47
Average repurchase price per share	[2],[3]	$ 128.80	$ 119.29
Total cost	[2]	$ 1,754	$ 5,604

[1] All shares repurchased in the open market have been retired and constitute authorized but unissued shares.

[2] Shares repurchased in the open market reflect repurchases settled during the three and nine months ended June 30, 2018. These amounts include repurchases traded but not yet settled on or before September 30, 2017 for the nine months, or March 31, 2018 for the three months, and exclude repurchases traded but not yet settled on or before June 30, 2018.

[3] Figures in the table may not recalculate exactly due to rounding. Average repurchase price per share is calculated based on unrounded numbers.