Share Repurchases in the Open Market (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014		Mar. 31, 2014
Stockholders' Equity Note [Abstract]
Shares repurchased in the open market	5	[1]	11	[1]
Weighted-average repurchase price per share	$ 217.61		$ 208.31
Total cost	$ 1,119		$ 2,210

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