Weighted Average Actuarial Assumptions (Detail)		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on plan assets	[1]	7.00%	7.00%	7.00%
Rate of increase in compensation levels for:
Benefit obligation	[2]			4.00%
Net periodic benefit cost	[2]			4.00%
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on plan assets	[1]	4.50%	3.92%
Rate of increase in compensation levels for:
Benefit obligation	[2]	3.20%	3.20%
Net periodic benefit cost	[2]	3.20%	3.00%
Other Postretirement Benefits | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate for benefit obligation	[3]	2.44%	1.91%	2.43%
Discount rate for net periodic benefit cost		1.91%	2.43%	2.59%
Pension Benefits | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate for benefit obligation	[3]	3.84%	3.62%	4.33%
Discount rate for net periodic benefit cost		3.62%	4.33%	4.27%
Pension Benefits | Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate for benefit obligation	[3]	2.70%	2.40%
Discount rate for net periodic benefit cost		2.40%	3.10%

[1] Primarily based on the targeted allocation, and evaluated for reasonableness by considering such factors as: (i) actual return on plan assets; (ii) historical rates of return on various asset classes in the portfolio; (iii) projections of returns on various asset classes; and (iv) current and prospective capital market conditions and economic forecasts.

[2] This assumption is not applicable for the U.S. plans in fiscal 2017 and 2016 due to the amendment of the U.S. qualified defined benefit pension plan in October 2015, which discontinued the employer provided credits effective after December 31, 2015.

[3] Represents a single weighted-average discount rate derived based on a cash flow matching analysis, with the projected benefit payments matching spot rates from a yield curve developed from high-quality corporate bonds.