Summary of Performance-based Shares Activity (Detail)	12 Months Ended
	Sep. 30, 2016 $ / shares shares
Weighted- Average Remaining Contractual Term
Outstanding at September 30, 2016	5 years 2 months 19 days
Aggregate Intrinsic Value
Stock price used to calculate aggregate intrinsic value	$ 82.7
Performance Awards
Shares
Beginning balance | shares	(1,263,962)
Granted | shares	604,219	[1]
Vested | shares	(645,320)
Unearned | shares	123,387
Forfeited | shares	(57,462)
Ending balance | shares	(1,042,012)
Weighted- Average Grant Date Fair Value
Beginning balance	$ 57.61
Granted	92.71	[1]
Vested	54.59
Unearned	54.59
Forfeited	73.07
Ending balance	$ 78.24
Weighted- Average Remaining Contractual Term
Outstanding at September 30, 2016	10 months 29 days
Aggregate Intrinsic Value
Outstanding at September 30, 2016	$ 86,000,000	[2]

[1] Represents the maximum number of performance-based shares which could be earned.

[2] Calculated by multiplying the closing stock price on the last trading day of fiscal 2016 of $82.70 by the number of instruments.