Long-Term Debt (Parenthetical) (Detail)	1 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2015	Jun. 30, 2017	Sep. 30, 2016
3.625% Senior Notes, due April 2023
Debt Instrument [Line Items]
Long-term debt interest rate	3.625%	3.625%	3.625%
Debt instruments maturity date	Apr. 30, 2023	Apr. 30, 2023	Apr. 30, 2023
U.S. Term Loan, due April 2020
Debt Instrument [Line Items]
Debt instruments maturity date		Apr. 30, 2020	Apr. 30, 2020