Summary of Option Activity (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Aggregate Intrinsic Value
Stock price used to calculate aggregate intrinsic value	$ 105.24
Employee Stock Option
Options
Beginning balance | shares	8,876,484
Granted | shares	1,671,344
Forfeited | shares	(386,136)
Exercised | shares	(3,045,816)
Ending balance | shares	7,115,876
Options exercisable at September 30, 2017 | shares	4,463,008
Options exercisable and expected to be vested at September 30, 2017 | shares	6,773,571	[1]
Weighted-Average Remaining Contractual Term
Outstanding at September 30, 2017	5 years 4 months 24 days
Options exercisable at September 30, 2017	3 years 7 months 6 days
Options exercisable and expected to vest at September 30, 2017	5 years 3 months 18 days	[1]
Weighted-Average Exercise Price Per Share
Beginning balance	$ 38.42
Granted	80.82
Forfeited	75.01
Exercised	29.62
Ending balance	50.17
Options exercisable at September 30, 2017	33.39
Options exercisable and expected to vest at September 30, 2017	$ 48.73	[1]
Aggregate Intrinsic Value
Outstanding at September 30, 2017 | $	$ 392	[2]
Options exercisable at September 30, 2017 | $	321	[2]
Options exercisable and expected to vest at September 30, 2017 | $	$ 383	[1],[2]

[1] Applies a forfeiture rate to unvested options outstanding at September 30, 2017 to estimate the options expected to vest in the future.

[2] Calculated using the closing stock price on the last trading day of fiscal 2017 of $105.24, less the option exercise price, multiplied by the number of instruments.