Pensions and Other Postretirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Reduction of Defined Benefit Plan Liability	$ 14.0
Recognition Period for Remeasured Benefit Plan Liability		27 months