Stockholders' Equity - Share Repurchases in the Open Market (Detail) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Stockholders' Equity Note [Abstract]
Shares repurchased in the open market | shares	26	[1]
Average repurchase price per share | $ / shares	$ 78.52	[2]
Total cost | $	$ 2,015

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

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