Weighted Average Actuarial Assumptions (Detail)	12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on plan assets	7.00%	[1]	7.50%	[1]
Rate of increase in compensation levels for:
Benefit obligation	4.50%		4.50%		4.50%
Net periodic benefit cost	4.50%		4.50%		4.50%
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate for benefit obligation	4.81%	[2]	3.85%	[2]	4.70%	[2]
Discount rate for net periodic benefit cost	3.85%		4.70%		5.25%
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate for benefit obligation	2.76%	[2]	2.21%	[2]	3.39%	[2]
Discount rate for net periodic benefit cost	2.21%		3.39%		3.45%

[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] Based on a “bond duration matching” methodology, which reflects the matching of projected plan liability cash flows to an average of high-quality corporate bond yield curves whose duration matches the projected cash flows.