Defined Benefit Plans - Components of Consolidated Net Periodic Benefit and Deferred Compensation Benefit Costs and Contributions Made (Detail) (Net periodic benefit cost [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Net periodic benefit cost [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 1.2	$ 0.8
Interest cost	3.4	2.6
Expected return on assets	(3.6)	(2.5)
Recognized net actuarial loss	0.4	0.5
Net periodic benefit expense	1.4	1.4
Contributions made during period	$ 3.4	$ 0.7